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Posted to jira@kafka.apache.org by GitBox <gi...@apache.org> on 2021/02/03 00:01:02 UTC
[GitHub] [kafka] cmccabe opened a new pull request #10030: Add KafkaEventQueue
cmccabe opened a new pull request #10030:
URL: https://github.com/apache/kafka/pull/10030
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[GitHub] [kafka] ijuma commented on pull request #10030: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
ijuma commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772102047
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[GitHub] [kafka] cmccabe commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772135933
It's also used in the broker, but that depends on the metadata module
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[GitHub] [kafka] junrao commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
junrao commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569890466
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
> Unless I'm missing something, the event that got prepended to the queue will be immediately run on the next iteration of the loop. There is no opportunity to prepend multiple deferred events to the toRun queue, since only one event can be prepended per loop run, and that event will be immediately run at the top of the loop.
Hmm, after the event is prepended, we continue to the next while loop before dequeuing and setting toRun, right? Then, in the next loop, we could be prepending the next deferred item before the previous one runs.
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570367570
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
@cmccabe What do you think about splitting this functionality into two types? For example:
1. `EventQueue` is a type which is responsible for ordering evens given the the insertion type and deadline. This type is thread-safe but doesn't instantiate thread(s). This type exposes methods for enqueuing and dequeuing events. The dequeuing method(s) can take in a "time" parameter and polls to see if there is an event ready. The dequeue method(s) would need to return the difference between "time" and the next closest event in the queue.
2. `SingleThreadEventExecutor` is a type which spawns a thread to dequeue events from the `EventQueue`, executes the `run` or `handleException` methods of the event and it is `AutoCloseable`.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
Okay. I suggested it because maybe unittests would be easier to write since the tests would have to deal with concurrency.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
@cmccabe What do you think about splitting this functionality into two types? For example:
1. `EventQueue` is a type which is responsible for ordering events given the the insertion type and deadline. This type is thread-safe but doesn't instantiate thread(s). This type exposes methods for enqueuing and dequeuing events. The dequeuing method(s) can take in a "time" parameter and polls to see if there is an event ready. The dequeue method(s) would need to return the difference between "time" and the next closest event in the queue.
2. `SingleThreadEventExecutor` is a type which spawns a thread to dequeue events from the `EventQueue`, executes the `run` or `handleException` methods of the event and it is `AutoCloseable`.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569818530
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
Review comment:
I think it's pretty standard for linked list insertion functions to overwrite the existing prev and next pointers of the object being inserted
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570442555
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
That's an interesting idea, but I'm not sure I see an advantage for this use-case. We only want a single thread here-- otherwise we would have to have locking in the controller and in the parts of the broker which use this queue. So the potential benefit that I can see from your proposal (allowing multiple executors) doesn't really apply here.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569781222
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
Review comment:
I added a comment saying that "Once the deadline has arrived, the event will be prepended to the queue"
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[GitHub] [kafka] cmccabe merged pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe merged pull request #10030:
URL: https://github.com/apache/kafka/pull/10030
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570367570
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
@cmccabe What do you think about splitting this functionality into two types? For example:
1. `EventQueue` is a type which is responsible for ordering events given the the insertion type and deadline. This type is thread-safe but doesn't instantiate thread(s). This type exposes methods for enqueuing and dequeuing events. The dequeuing method(s) can take in a "time" parameter and polls to see if there is an event ready. The dequeue method(s) would need to return the difference between "time" and the next closest event in the queue.
2. `SingleThreadEventExecutor` is a type which spawns a thread to dequeue events from the `EventQueue`, executes the `run` or `handleException` methods of the event and it is `AutoCloseable`.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569797937
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
Review comment:
good point... we don't need to lock here, since the caller already does.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569801978
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
Unless I'm missing something, the event that got prepended to the queue will be immediately run on the next iteration of the loop. There is no opportunity to prepend multiple deferred events to the toRun queue, since only one event can be prepended per loop run, and that event will be immediately run at the top of the loop.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569802821
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
+ try {
+ eventHandler.cancelDeferred(tag);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void beginShutdown(String source, Event newCleanupEvent,
+ TimeUnit timeUnit, long timeSpan) {
+ if (timeSpan < 0) {
+ throw new IllegalArgumentException("beginShutdown must be called with a " +
+ "non-negative timeout.");
+ }
+ Objects.requireNonNull(newCleanupEvent);
+ lock.lock();
+ try {
+ if (cleanupEvent != null) {
+ log.debug("{}: Event queue is already shut down.", source);
+ return;
+ }
+ log.info("{}: shutting down event queue.", source);
+ cleanupEvent = newCleanupEvent;
+ long newClosingTimeNs = time.nanoseconds() + timeUnit.toNanos(timeSpan);
+ if (closingTimeNs >= newClosingTimeNs)
+ closingTimeNs = newClosingTimeNs;
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void wakeup() {
+ lock.lock();
+ try {
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void close() throws InterruptedException {
+ beginShutdown("KafkaEventQueue#close");
+ eventHandlerThread.join();
+ log.info("closed event queue.");
Review comment:
I think it's useful since events can still be executed after beginShutdown is called. joining the thread is an important milestone (and won't happen if a buggy event hangs) so good to log.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569812521
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ enqueue(EventInsertionType.DEFERRED, tag, deadlineNsCalculator, event);
+ }
+
+ /**
+ * Cancel a deferred event.
+ *
+ * @param tag The unique tag for the event to be cancelled. Must be
+ * non-null. If the event with the tag has not been
+ * scheduled, this call will be ignored.
+ */
+ void cancelDeferred(String tag);
+
+ enum EventInsertionType {
+ PREPEND,
+ APPEND,
+ DEFERRED;
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param insertionType How to insert the event.
+ * PREPEND means insert the event as the first thing
+ * to run. APPEND means insert the event as the last
+ * thing to run. DEFERRED means insert the event to
+ * run after a delay.
Review comment:
I will change the description to reflect the fact that this function supports PREPEND and DEFERRED, so it's not always "FIFO order".
How to use deferred events is described in more detail in `scheduleDeferred`
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569799998
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
Review comment:
I think it's probably better to handle it through the Event callback, since all the other errors are handled that way. We do not throw exceptions from any of the enqueue functions-- they always succeed, and whatever error or timeout happens is handled through the events.
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[GitHub] [kafka] cmccabe commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772738349
re-trigger jenkins to try to get a green build
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[GitHub] [kafka] junrao commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
junrao commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569666673
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
Review comment:
Do we need the lock here again since the caller already locks?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
Review comment:
Since this is unexpected, should we just throw the exception directly back to the caller?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
Review comment:
Perhaps we could document the ordering guarantee with the deferred event compared with other types of events?
##########
File path: metadata/src/test/java/org/apache/kafka/queue/KafkaEventQueueTest.java
##########
@@ -0,0 +1,239 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Supplier;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.MockTime;
+import org.apache.kafka.common.utils.Time;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+
+@Timeout(value = 60)
+public class KafkaEventQueueTest {
+ private static class FutureEvent<T> implements EventQueue.Event {
+ private final CompletableFuture<T> future;
+ private final Supplier<T> supplier;
+
+ FutureEvent(CompletableFuture<T> future, Supplier<T> supplier) {
+ this.future = future;
+ this.supplier = supplier;
+ }
+
+ @Override
+ public void run() throws Exception {
+ T value = supplier.get();
+ future.complete(value);
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ future.completeExceptionally(e);
+ }
+ }
+
+ @Test
+ public void testCreateAndClose() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testCreateAndClose");
+ queue.close();
+ }
+
+ @Test
+ public void testHandleEvents() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testHandleEvents");
+ AtomicInteger numEventsExecuted = new AtomicInteger(0);
+ CompletableFuture<Integer> future1 = new CompletableFuture<>();
+ queue.prepend(new FutureEvent<>(future1, () -> {
+ assertEquals(1, numEventsExecuted.incrementAndGet());
+ return 1;
+ }));
+ CompletableFuture<Integer> future2 = new CompletableFuture<>();
+ queue.appendWithDeadline(Time.SYSTEM.nanoseconds() + TimeUnit.SECONDS.toNanos(30),
Review comment:
Strictly speaking, with system time, this event could time out before the first future is executed. Should we use mock time?
##########
File path: metadata/src/test/java/org/apache/kafka/queue/KafkaEventQueueTest.java
##########
@@ -0,0 +1,239 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Supplier;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.MockTime;
+import org.apache.kafka.common.utils.Time;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+
+@Timeout(value = 60)
+public class KafkaEventQueueTest {
+ private static class FutureEvent<T> implements EventQueue.Event {
+ private final CompletableFuture<T> future;
+ private final Supplier<T> supplier;
+
+ FutureEvent(CompletableFuture<T> future, Supplier<T> supplier) {
+ this.future = future;
+ this.supplier = supplier;
+ }
+
+ @Override
+ public void run() throws Exception {
+ T value = supplier.get();
+ future.complete(value);
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ future.completeExceptionally(e);
+ }
+ }
+
+ @Test
+ public void testCreateAndClose() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testCreateAndClose");
+ queue.close();
+ }
+
+ @Test
+ public void testHandleEvents() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testHandleEvents");
+ AtomicInteger numEventsExecuted = new AtomicInteger(0);
+ CompletableFuture<Integer> future1 = new CompletableFuture<>();
+ queue.prepend(new FutureEvent<>(future1, () -> {
+ assertEquals(1, numEventsExecuted.incrementAndGet());
+ return 1;
+ }));
+ CompletableFuture<Integer> future2 = new CompletableFuture<>();
+ queue.appendWithDeadline(Time.SYSTEM.nanoseconds() + TimeUnit.SECONDS.toNanos(30),
+ new FutureEvent<>(future2, () -> {
+ assertEquals(2, numEventsExecuted.incrementAndGet());
+ return 2;
+ }));
+ CompletableFuture<Integer> future3 = new CompletableFuture<>();
+ queue.append(new FutureEvent<>(future3, () -> {
+ assertEquals(3, numEventsExecuted.incrementAndGet());
+ return 3;
+ }));
+ assertEquals(Integer.valueOf(1), future1.get());
+ assertEquals(Integer.valueOf(3), future3.get());
+ assertEquals(Integer.valueOf(2), future2.get());
+ CompletableFuture<Integer> future4 = new CompletableFuture<>();
+ queue.appendWithDeadline(Time.SYSTEM.nanoseconds() + TimeUnit.SECONDS.toNanos(30),
+ new FutureEvent<>(future4, () -> {
+ assertEquals(4, numEventsExecuted.incrementAndGet());
+ return 4;
+ }));
+ future4.get();
+ queue.beginShutdown("testHandleEvents");
+ queue.close();
+ }
+
+ @Test
+ public void testTimeouts() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testTimeouts");
+ AtomicInteger numEventsExecuted = new AtomicInteger(0);
+ CompletableFuture<Integer> future1 = new CompletableFuture<>();
+ queue.append(new FutureEvent<>(future1, () -> {
+ assertEquals(1, numEventsExecuted.incrementAndGet());
+ return 1;
+ }));
+ CompletableFuture<Integer> future2 = new CompletableFuture<>();
+ queue.append(new FutureEvent<>(future2, () -> {
+ assertEquals(2, numEventsExecuted.incrementAndGet());
+ Time.SYSTEM.sleep(1);
+ return 2;
+ }));
+ CompletableFuture<Integer> future3 = new CompletableFuture<>();
+ queue.appendWithDeadline(Time.SYSTEM.nanoseconds() + 1,
+ new FutureEvent<>(future3, () -> {
+ numEventsExecuted.incrementAndGet();
+ return 3;
+ }));
+ CompletableFuture<Integer> future4 = new CompletableFuture<>();
+ queue.append(new FutureEvent<>(future4, () -> {
+ numEventsExecuted.incrementAndGet();
+ return 4;
+ }));
+ assertEquals(Integer.valueOf(1), future1.get());
+ assertEquals(Integer.valueOf(2), future2.get());
+ assertEquals(Integer.valueOf(4), future4.get());
+ assertEquals(TimeoutException.class,
+ assertThrows(ExecutionException.class,
+ () -> future3.get()).getCause().getClass());
+ queue.close();
+ assertEquals(3, numEventsExecuted.get());
+ }
+
+ @Test
+ public void testScheduleDeferred() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testAppendDeferred");
+
+ // Wait for the deferred event to happen after the non-deferred event.
+ // It may not happpen every time, so we keep trying until it does.
Review comment:
typo happpen
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
+ try {
+ eventHandler.cancelDeferred(tag);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void beginShutdown(String source, Event newCleanupEvent,
+ TimeUnit timeUnit, long timeSpan) {
+ if (timeSpan < 0) {
+ throw new IllegalArgumentException("beginShutdown must be called with a " +
+ "non-negative timeout.");
+ }
+ Objects.requireNonNull(newCleanupEvent);
+ lock.lock();
+ try {
+ if (cleanupEvent != null) {
+ log.debug("{}: Event queue is already shut down.", source);
+ return;
+ }
+ log.info("{}: shutting down event queue.", source);
+ cleanupEvent = newCleanupEvent;
+ long newClosingTimeNs = time.nanoseconds() + timeUnit.toNanos(timeSpan);
+ if (closingTimeNs >= newClosingTimeNs)
+ closingTimeNs = newClosingTimeNs;
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void wakeup() {
+ lock.lock();
+ try {
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void close() throws InterruptedException {
+ beginShutdown("KafkaEventQueue#close");
+ eventHandlerThread.join();
+ log.info("closed event queue.");
Review comment:
Is this necessary since we already have an info logging in beginShutdown().
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
Since now can change after each while loop, it's possible that deferred events are prepended to the queue in reverse order. Does that matter?
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569811507
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
Review comment:
We need to support absolute times in order to support things like `EarliestDeadlineFunction`, and mixing relative and absolute times is kind of confusing.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569824001
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
Review comment:
> Let's document these two methods
Sure. I will add some JavaDoc.
> Any thoughts on why this design instead of not allowing run to throw a checked exception? For example:
Checked exceptions are sort of a failed idea. This would just force you to wrap all the checked exceptions that the event could throw, and unwrap them in handleException. That would not help the clarity of the controller code.
Also, implementing Runnable isn't really useful here because Java 8 lambdas can be used on any single-function interface, not just Runnable.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569806358
##########
File path: metadata/src/test/java/org/apache/kafka/queue/KafkaEventQueueTest.java
##########
@@ -0,0 +1,239 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Supplier;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.MockTime;
+import org.apache.kafka.common.utils.Time;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+
+@Timeout(value = 60)
+public class KafkaEventQueueTest {
+ private static class FutureEvent<T> implements EventQueue.Event {
+ private final CompletableFuture<T> future;
+ private final Supplier<T> supplier;
+
+ FutureEvent(CompletableFuture<T> future, Supplier<T> supplier) {
+ this.future = future;
+ this.supplier = supplier;
+ }
+
+ @Override
+ public void run() throws Exception {
+ T value = supplier.get();
+ future.complete(value);
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ future.completeExceptionally(e);
+ }
+ }
+
+ @Test
+ public void testCreateAndClose() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testCreateAndClose");
+ queue.close();
+ }
+
+ @Test
+ public void testHandleEvents() throws Exception {
+ KafkaEventQueue queue =
+ new KafkaEventQueue(Time.SYSTEM, new LogContext(), "testHandleEvents");
+ AtomicInteger numEventsExecuted = new AtomicInteger(0);
+ CompletableFuture<Integer> future1 = new CompletableFuture<>();
+ queue.prepend(new FutureEvent<>(future1, () -> {
+ assertEquals(1, numEventsExecuted.incrementAndGet());
+ return 1;
+ }));
+ CompletableFuture<Integer> future2 = new CompletableFuture<>();
+ queue.appendWithDeadline(Time.SYSTEM.nanoseconds() + TimeUnit.SECONDS.toNanos(30),
Review comment:
I will enlarge the timeout to 60 seconds so that it's equal to the test timeout as a whole. Assuming that timeout is reasonable (and I think it is) then there should be no issue...
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[GitHub] [kafka] cmccabe commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-773648975
Test failure is `org.apache.kafka.connect.mirror.integration.MirrorConnectorsIntegrationSSLTest` which is not related.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569832568
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
Review comment:
I will add a line to the JavaDoc stating "Events whose deadlines are only a few nanoseconds apart may be executed in any order"
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569829682
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
Review comment:
fair point. let's move this outside the lock.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570442555
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
That's an interesting idea, but I'm not sure I see an advantage for this use-case. We only want a single thread here-- otherwise we would have to have locking in the controller and in the parts of the broker which use this queue. So the potential benefit that I can see from your proposal (allowing multiple executors) doesn't really apply here.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
I looked at this again, and yes, you are right: it should just be `toRun = eventContext`. Fixed.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569817844
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
Review comment:
ok
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[GitHub] [kafka] junrao commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
junrao commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570453181
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,263 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.OptionalLong;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ /**
+ * Run the event.
+ */
+ void run() throws Exception;
+
+ /**
+ * Handle an exception that was either generated by running the event, or by the
+ * event queue's inability to run the event.
+ *
+ * @param e The exception. This will be a TimeoutException if the event hit
+ * its deadline before it could be scheduled.
+ * It will be a RejectedExecutionException if the event could not be
+ * scheduled because the event queue has already been closed.
+ * Otherweise, it will be whatever exception was thrown by run().
+ */
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof RejectedExecutionException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class NoDeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ public static final NoDeadlineFunction INSTANCE = new NoDeadlineFunction();
+
+ @Override
+ public OptionalLong apply(OptionalLong ignored) {
+ return OptionalLong.empty();
+ }
+ }
+
+ class DeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public OptionalLong apply(OptionalLong ignored) {
+ return OptionalLong.of(deadlineNs);
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public OptionalLong apply(OptionalLong prevDeadlineNs) {
+ if (!prevDeadlineNs.isPresent()) {
+ return OptionalLong.of(newDeadlineNs);
+ } else if (prevDeadlineNs.getAsLong() < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return OptionalLong.of(newDeadlineNs);
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, NoDeadlineFunction.INSTANCE, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, NoDeadlineFunction.INSTANCE, event);
+ }
+
+ /**
+ * Add an event to the end of the queue.
+ *
+ * @param deadlineNs The deadline for starting the event, in monotonic
+ * nanoseconds. If the event has not started by this
+ * deadline, handleException is called with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, new DeadlineFunction(deadlineNs), event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or empty if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * Once the deadline has arrived, the event will be
+ * prepended to the queue. Events whose deadlines are
Review comment:
"the event will be prepended to the queue" : This is no longer true in the implementation.
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[GitHub] [kafka] ijuma commented on pull request #10030: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
ijuma commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772102047
Thanks for the PR. Why does this have to be in the `common` package?
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569820132
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
Review comment:
handleException really should not throw. But I will add an ERROR log message if it does.
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[GitHub] [kafka] ijuma commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
ijuma commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772361384
@junrao Do you have time to help review this?
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569928716
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
There is a `continue;` at line 219 so that means that `toRun` is not set in this iteration of the loop did you mean to have this instead: `toRun = eventContext;`
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569716767
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
Review comment:
Which future? Did you mean `Event`. I assume that `deadlineNs` is the deadline for scheduling/executing the `run` method. The `run` method can take longer than `deadlineNs`.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ enqueue(EventInsertionType.DEFERRED, tag, deadlineNsCalculator, event);
+ }
+
+ /**
+ * Cancel a deferred event.
+ *
+ * @param tag The unique tag for the event to be cancelled. Must be
+ * non-null. If the event with the tag has not been
+ * scheduled, this call will be ignored.
+ */
+ void cancelDeferred(String tag);
+
+ enum EventInsertionType {
+ PREPEND,
+ APPEND,
+ DEFERRED;
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param insertionType How to insert the event.
+ * PREPEND means insert the event as the first thing
+ * to run. APPEND means insert the event as the last
+ * thing to run. DEFERRED means insert the event to
+ * run after a delay.
Review comment:
The headline description says "Enqueue an event to be run in FIFO order." but looking the param description it doesn't looking like it is FIFO order since it support prepend, append and deferred.
What do you mean by DEFEREED? How is the delay specified? I see the param `deadlineNsCalculator` but it looks like this describe the maximum amount of time this event is allowed to stay in the queue before it is cancelled by the queue.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ enqueue(EventInsertionType.DEFERRED, tag, deadlineNsCalculator, event);
+ }
+
+ /**
+ * Cancel a deferred event.
+ *
+ * @param tag The unique tag for the event to be cancelled. Must be
+ * non-null. If the event with the tag has not been
+ * scheduled, this call will be ignored.
+ */
+ void cancelDeferred(String tag);
+
+ enum EventInsertionType {
+ PREPEND,
+ APPEND,
+ DEFERRED;
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param insertionType How to insert the event.
+ * PREPEND means insert the event as the first thing
+ * to run. APPEND means insert the event as the last
+ * thing to run. DEFERRED means insert the event to
+ * run after a delay.
+ * @param tag If this is non-null, the unique tag to use for
+ * this event. If an event with this tag already
+ * exists, it will be cancelled.
+ * @param deadlineNsCalculator If this is non-null, it is a function which takes
+ * as an argument the existing deadline for the
+ * event with this tag (or null if the event has no
+ * tag, or if there is none such), and produces the
+ * deadline to use for this event (or null to use
+ * none.)
+ * @param event The event to enqueue.
+ */
+ void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event);
+
+ /**
+ * Asynchronously shut down the event queue with no unnecessary delay.
+ * @see #beginShutdown(String, Event, TimeUnit, long)
+ *
+ * @param source The source of the shutdown.
+ */
+ default void beginShutdown(String source) {
+ beginShutdown(source, new VoidEvent());
+ }
+
+ /**
+ * Asynchronously shut down the event queue with no unnecessary delay.
+ *
+ * @param source The source of the shutdown.
+ * @param cleanupEvent The mandatory event to invoke after all other events have
+ * been processed.
+ * @see #beginShutdown(String, Event, TimeUnit, long)
+ */
+ default void beginShutdown(String source, Event cleanupEvent) {
+ beginShutdown(source, cleanupEvent, TimeUnit.SECONDS, 0);
+ }
+
+ /**
+ * Asynchronously shut down the event queue.
+ *
+ * No new events will be accepted, and the timeout will be initiated
+ * for all existing events.
+ *
+ * @param source The source of the shutdown.
+ * @param cleanupEvent The mandatory event to invoke after all other events have
+ * been processed.
+ * @param timeUnit The time unit to use for the timeout.
+ * @param timeSpan The amount of time to use for the timeout.
+ * Once the timeout elapses, any remaining queued
+ * events will get a
+ * @{org.apache.kafka.common.errors.TimeoutException}.
+ */
+ void beginShutdown(String source, Event cleanupEvent, TimeUnit timeUnit, long timeSpan);
Review comment:
In Java the unit of measure `timeUnit` and scalar `timeSpan` are declare in reverse order. For example:
```java
void beginShutdown(String source, Event cleanupEvent, long timeSpan, TimeUnit timeUnit);
```
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
Review comment:
Hmm. Does this mean that `DEFERRED` events cannot timeout? How about making the two threshold described independently when the event is enqueued?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
Review comment:
Hmm. This is surprising to me. The caller scheduling the event passed illegal arguments to the queue. Shouldn't this method throw an IllegalArgumentException instead of sending an exception to the event?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
Review comment:
The headline description says "Schedule an event to be run at a specific time" yet this param's description seem to indicate a different behavior.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
+ try {
+ eventHandler.cancelDeferred(tag);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void beginShutdown(String source, Event newCleanupEvent,
+ TimeUnit timeUnit, long timeSpan) {
+ if (timeSpan < 0) {
+ throw new IllegalArgumentException("beginShutdown must be called with a " +
+ "non-negative timeout.");
+ }
+ Objects.requireNonNull(newCleanupEvent);
+ lock.lock();
+ try {
+ if (cleanupEvent != null) {
+ log.debug("{}: Event queue is already shut down.", source);
+ return;
+ }
+ log.info("{}: shutting down event queue.", source);
+ cleanupEvent = newCleanupEvent;
+ long newClosingTimeNs = time.nanoseconds() + timeUnit.toNanos(timeSpan);
+ if (closingTimeNs >= newClosingTimeNs)
+ closingTimeNs = newClosingTimeNs;
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void wakeup() {
+ lock.lock();
+ try {
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
Review comment:
How about moving this concurrency complexity to `EventHandler` by adding a method called `EventHandler::wakeup`?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
Review comment:
How about "Insert the EventContext other in the circularly linked list after this node." I would also mention that this requires that `other.isSingleton()` is true. Should we check for that in this implementation?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueueClosedException.java
##########
@@ -0,0 +1,27 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+
+public class EventQueueClosedException extends RuntimeException {
Review comment:
Can we use Java's existing type `java.util.concurrent.RejectedExecutionException`?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
Review comment:
Do we want to handle the case where `Event::handleException` throws?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
Review comment:
Let's document these two methods. For example, looking at the implementation it looks like `handleException` needs to handle:
1. Exceptions thrown by `Event::run`
2. Exception passed by the `EventQueue` like `EventQueueClosedException`, `TimeoutException`, anything else?
Any thoughts on why this design instead of not allowing `run` to throw a checked exception? For example:
```java
interface Event extends Runnable {
default void cancel(Throwable e) {}
}
```
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
Review comment:
We can use `OptionalLong`.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
Review comment:
We can move this lock to `EventHandler::cancelDeferred`. `EventHandler` is already handling concurrent access to the fields in this object.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
Review comment:
We can use `Optional<String>`.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
Review comment:
Hmm. This can cause an event with delay X to be schedule after an event with delay Y even if X < Y.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
Review comment:
Looks like we are calling unknown code while holding a lock.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
Review comment:
It would be interesting to explain this design. I get the impression that we are interesting in rescheduling events that haven't triggered.
One way to change the deadline is to specified the previous event that is being rescheduled. E.g.
```java
rescheduleDeferred(Event oldEvent, Function<Long, Long> deadlineNsCalculator, Event newEvent);
```
This API allows the deadline to either increase or decrease. Are both cases used by the Controller?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
Review comment:
Hmm. The word "delay" suggests relative time but it looks like the keys are absolute times. How about `scheduleMap`?
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
+ try {
+ eventHandler.cancelDeferred(tag);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void beginShutdown(String source, Event newCleanupEvent,
+ TimeUnit timeUnit, long timeSpan) {
+ if (timeSpan < 0) {
+ throw new IllegalArgumentException("beginShutdown must be called with a " +
+ "non-negative timeout.");
+ }
+ Objects.requireNonNull(newCleanupEvent);
+ lock.lock();
+ try {
+ if (cleanupEvent != null) {
+ log.debug("{}: Event queue is already shut down.", source);
Review comment:
".. shutting down"
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
Review comment:
Looking at the implementation, it looks like this Long is an absolute time. Is there a reason why absolute times are used instead of relative times like delay and timeout?
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[GitHub] [kafka] cmccabe commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-773648975
Test failure is `org.apache.kafka.connect.mirror.integration.MirrorConnectorsIntegrationSSLTest` which is not related.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569813199
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or null if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * @param event The event to schedule.
+ */
+ default void scheduleDeferred(String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ enqueue(EventInsertionType.DEFERRED, tag, deadlineNsCalculator, event);
+ }
+
+ /**
+ * Cancel a deferred event.
+ *
+ * @param tag The unique tag for the event to be cancelled. Must be
+ * non-null. If the event with the tag has not been
+ * scheduled, this call will be ignored.
+ */
+ void cancelDeferred(String tag);
+
+ enum EventInsertionType {
+ PREPEND,
+ APPEND,
+ DEFERRED;
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param insertionType How to insert the event.
+ * PREPEND means insert the event as the first thing
+ * to run. APPEND means insert the event as the last
+ * thing to run. DEFERRED means insert the event to
+ * run after a delay.
+ * @param tag If this is non-null, the unique tag to use for
+ * this event. If an event with this tag already
+ * exists, it will be cancelled.
+ * @param deadlineNsCalculator If this is non-null, it is a function which takes
+ * as an argument the existing deadline for the
+ * event with this tag (or null if the event has no
+ * tag, or if there is none such), and produces the
+ * deadline to use for this event (or null to use
+ * none.)
+ * @param event The event to enqueue.
+ */
+ void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event);
+
+ /**
+ * Asynchronously shut down the event queue with no unnecessary delay.
+ * @see #beginShutdown(String, Event, TimeUnit, long)
+ *
+ * @param source The source of the shutdown.
+ */
+ default void beginShutdown(String source) {
+ beginShutdown(source, new VoidEvent());
+ }
+
+ /**
+ * Asynchronously shut down the event queue with no unnecessary delay.
+ *
+ * @param source The source of the shutdown.
+ * @param cleanupEvent The mandatory event to invoke after all other events have
+ * been processed.
+ * @see #beginShutdown(String, Event, TimeUnit, long)
+ */
+ default void beginShutdown(String source, Event cleanupEvent) {
+ beginShutdown(source, cleanupEvent, TimeUnit.SECONDS, 0);
+ }
+
+ /**
+ * Asynchronously shut down the event queue.
+ *
+ * No new events will be accepted, and the timeout will be initiated
+ * for all existing events.
+ *
+ * @param source The source of the shutdown.
+ * @param cleanupEvent The mandatory event to invoke after all other events have
+ * been processed.
+ * @param timeUnit The time unit to use for the timeout.
+ * @param timeSpan The amount of time to use for the timeout.
+ * Once the timeout elapses, any remaining queued
+ * events will get a
+ * @{org.apache.kafka.common.errors.TimeoutException}.
+ */
+ void beginShutdown(String source, Event cleanupEvent, TimeUnit timeUnit, long timeSpan);
Review comment:
fair enough, I will put timeSpan first
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569825102
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
Review comment:
In general I would prefer to do all the error handling in one place (the event). Having to handle errors in multiple places is more difficult.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569827578
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, __ -> deadlineNs, event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
Review comment:
> One way to change the deadline is to specified the previous event that is being rescheduled
Having to store the previous event object somewhere would be very annoying. Since the thread triggering deferred events is often not the controller thread itself, it would require complex locking or volatile objects. Also then you run into issues like should the equals function be used, or object identity.
It's a lot easier to just pass a string (which is immutable). This also has the nice effect of describing the deferred event.
> This API allows the deadline to either increase or decrease. Are both cases used by the Controller?
In the controller we are mainly interested in making the deadline closer to "now" (decreasing it) or cancelling the deferred event.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569821586
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
Review comment:
I'd rather not here.
Checking strings for null seems like idiomatic Java. Strings have always been nullable reference types. This is different than the OptionalLong case above, where it always felt awkward checking if a numeric type was null. At least that's my feeling.
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[GitHub] [kafka] junrao commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
junrao commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569820385
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
Hmm, after the event is prepended, we continue to the next while loop before dequeuing and setting toRun, right? Then, in the next loop, we could be prepending the next deferred item before the previous one runs.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570450458
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
Review comment:
I looked at this again, and yes, you are right: it should just be `toRun = eventContext`. Fixed.
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570462338
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
Okay. I suggested it because maybe unittests would be easier to write since the tests would have to deal with concurrency.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569814344
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueueClosedException.java
##########
@@ -0,0 +1,27 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+
+public class EventQueueClosedException extends RuntimeException {
Review comment:
Good idea. I will just use that exception instead.
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[GitHub] [kafka] jsancio commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
jsancio commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570367570
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
Review comment:
@cmccabe What do you think about splitting this functionality into two types? For example:
1. `EventQueue` is a type which is responsible for ordering evens given the the insertion type and deadline. This type is thread-safe but doesn't instantiate thread(s). This type exposes methods for enqueuing and dequeuing events. The dequeuing method(s) can take in a "time" parameter and polls to see if there is an event ready. The dequeue method(s) would need to return the difference between "time" and the next closest event in the queue.
2. `SingleThreadEventExecutor` is a type which spawns a thread to dequeue events from the `EventQueue`, executes the `run` or `handleException` methods of the event and it is `AutoCloseable`.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569824844
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
Review comment:
We can call it `deadlineMap`
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[GitHub] [kafka] junrao commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
junrao commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r570453181
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,263 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.OptionalLong;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ /**
+ * Run the event.
+ */
+ void run() throws Exception;
+
+ /**
+ * Handle an exception that was either generated by running the event, or by the
+ * event queue's inability to run the event.
+ *
+ * @param e The exception. This will be a TimeoutException if the event hit
+ * its deadline before it could be scheduled.
+ * It will be a RejectedExecutionException if the event could not be
+ * scheduled because the event queue has already been closed.
+ * Otherweise, it will be whatever exception was thrown by run().
+ */
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof RejectedExecutionException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class NoDeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ public static final NoDeadlineFunction INSTANCE = new NoDeadlineFunction();
+
+ @Override
+ public OptionalLong apply(OptionalLong ignored) {
+ return OptionalLong.empty();
+ }
+ }
+
+ class DeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public OptionalLong apply(OptionalLong ignored) {
+ return OptionalLong.of(deadlineNs);
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<OptionalLong, OptionalLong> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public OptionalLong apply(OptionalLong prevDeadlineNs) {
+ if (!prevDeadlineNs.isPresent()) {
+ return OptionalLong.of(newDeadlineNs);
+ } else if (prevDeadlineNs.getAsLong() < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return OptionalLong.of(newDeadlineNs);
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, NoDeadlineFunction.INSTANCE, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, NoDeadlineFunction.INSTANCE, event);
+ }
+
+ /**
+ * Add an event to the end of the queue.
+ *
+ * @param deadlineNs The deadline for starting the event, in monotonic
+ * nanoseconds. If the event has not started by this
+ * deadline, handleException is called with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
+ * @param event The event to append.
+ */
+ default void appendWithDeadline(long deadlineNs, Event event) {
+ enqueue(EventInsertionType.APPEND, null, new DeadlineFunction(deadlineNs), event);
+ }
+
+ /**
+ * Schedule an event to be run at a specific time.
+ *
+ * @param tag If this is non-null, the unique tag to use for this
+ * event. If an event with this tag already exists, it
+ * will be cancelled.
+ * @param deadlineNsCalculator A function which takes as an argument the existing
+ * deadline for the event with this tag (or empty if the
+ * event has no tag, or if there is none such), and
+ * produces the deadline to use for this event.
+ * Once the deadline has arrived, the event will be
+ * prepended to the queue. Events whose deadlines are
Review comment:
"the event will be prepended to the queue" : This is no longer true in the implementation.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569802821
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
+ // The deferred event is ready to run. Prepend it to the
+ // queue. (The value for deferred events is a schedule time
+ // rather than a timeout.)
+ remove(eventContext);
+ head.insertAfter(eventContext);
+ } else {
+ // not a deferred event, so it is a deadline, and it is timed out.
+ remove(eventContext);
+ toTimeout = eventContext;
+ }
+ continue;
+ } else if (closingTimeNs <= now) {
+ remove(eventContext);
+ toTimeout = eventContext;
+ continue;
+ }
+ awaitNs = timeoutNs - now;
+ }
+ if (head.next == head) {
+ if ((closingTimeNs != Long.MAX_VALUE) && delayMap.isEmpty()) {
+ // If there are no more entries to process, and the queue is
+ // closing, exit the thread.
+ return;
+ }
+ } else {
+ toRun = head.next;
+ remove(toRun);
+ continue;
+ }
+ if (closingTimeNs != Long.MAX_VALUE) {
+ long now = time.nanoseconds();
+ if (awaitNs > closingTimeNs - now) {
+ awaitNs = closingTimeNs - now;
+ }
+ }
+ if (awaitNs == Long.MAX_VALUE) {
+ cond.await();
+ } else {
+ cond.awaitNanos(awaitNs);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ private void enqueue(EventContext eventContext,
+ Function<Long, Long> deadlineNsCalculator) {
+ lock.lock();
+ try {
+ Long existingDeadlineNs = null;
+ if (eventContext.tag != null) {
+ EventContext toRemove =
+ tagToEventContext.put(eventContext.tag, eventContext);
+ if (toRemove != null) {
+ existingDeadlineNs = toRemove.deadlineNs;
+ remove(toRemove);
+ }
+ }
+ Long deadlineNs = deadlineNsCalculator.apply(existingDeadlineNs);
+ boolean queueWasEmpty = head.isSingleton();
+ boolean shouldSignal = false;
+ switch (eventContext.insertionType) {
+ case APPEND:
+ head.insertBefore(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case PREPEND:
+ head.insertAfter(eventContext);
+ if (queueWasEmpty) {
+ shouldSignal = true;
+ }
+ break;
+ case DEFERRED:
+ if (deadlineNs == null) {
+ eventContext.completeWithException(new RuntimeException(
+ "You must specify a deadline for deferred events."));
+ return;
+ }
+ break;
+ }
+ if (deadlineNs != null) {
+ long insertNs = deadlineNs;
+ long prevStartNs = delayMap.isEmpty() ? Long.MAX_VALUE : delayMap.firstKey();
+ // If the time in nanoseconds is already taken, take the next one.
+ while (delayMap.putIfAbsent(insertNs, eventContext) != null) {
+ insertNs++;
+ }
+ eventContext.deadlineNs = insertNs;
+ // If the new timeout is before all the existing ones, wake up the
+ // timeout thread.
+ if (insertNs <= prevStartNs) {
+ shouldSignal = true;
+ }
+ }
+ if (shouldSignal) {
+ cond.signal();
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public void cancelDeferred(String tag) {
+ EventContext eventContext = tagToEventContext.get(tag);
+ if (eventContext != null) {
+ remove(eventContext);
+ }
+ }
+ }
+
+ private final Time time;
+ private final ReentrantLock lock;
+ private final Logger log;
+ private final EventHandler eventHandler;
+ private final Thread eventHandlerThread;
+
+ /**
+ * The time in monotonic nanoseconds when the queue is closing, or Long.MAX_VALUE if
+ * the queue is not currently closing.
+ */
+ private long closingTimeNs;
+
+ private Event cleanupEvent;
+
+ public KafkaEventQueue(Time time,
+ LogContext logContext,
+ String threadNamePrefix) {
+ this.time = time;
+ this.lock = new ReentrantLock();
+ this.log = logContext.logger(KafkaEventQueue.class);
+ this.eventHandler = new EventHandler();
+ this.eventHandlerThread = new KafkaThread(threadNamePrefix + "EventHandler",
+ this.eventHandler, false);
+ this.closingTimeNs = Long.MAX_VALUE;
+ this.cleanupEvent = null;
+ this.eventHandlerThread.start();
+ }
+
+ @Override
+ public void enqueue(EventInsertionType insertionType,
+ String tag,
+ Function<Long, Long> deadlineNsCalculator,
+ Event event) {
+ lock.lock();
+ try {
+ EventContext eventContext = new EventContext(event, insertionType, tag);
+ if (closingTimeNs != Long.MAX_VALUE) {
+ eventContext.completeWithException(new EventQueueClosedException());
+ } else {
+ eventHandler.enqueue(eventContext,
+ deadlineNsCalculator == null ? __ -> null : deadlineNsCalculator);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void cancelDeferred(String tag) {
+ lock.lock();
+ try {
+ eventHandler.cancelDeferred(tag);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void beginShutdown(String source, Event newCleanupEvent,
+ TimeUnit timeUnit, long timeSpan) {
+ if (timeSpan < 0) {
+ throw new IllegalArgumentException("beginShutdown must be called with a " +
+ "non-negative timeout.");
+ }
+ Objects.requireNonNull(newCleanupEvent);
+ lock.lock();
+ try {
+ if (cleanupEvent != null) {
+ log.debug("{}: Event queue is already shut down.", source);
+ return;
+ }
+ log.info("{}: shutting down event queue.", source);
+ cleanupEvent = newCleanupEvent;
+ long newClosingTimeNs = time.nanoseconds() + timeUnit.toNanos(timeSpan);
+ if (closingTimeNs >= newClosingTimeNs)
+ closingTimeNs = newClosingTimeNs;
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void wakeup() {
+ lock.lock();
+ try {
+ eventHandler.cond.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ @Override
+ public void close() throws InterruptedException {
+ beginShutdown("KafkaEventQueue#close");
+ eventHandlerThread.join();
+ log.info("closed event queue.");
Review comment:
I think it's useful since events can still be executed after beginShutdown is called. joining the thread is an important milestone (and won't happen if a buggy event gets stuck) so good to log.
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[GitHub] [kafka] cmccabe commented on pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#issuecomment-772123503
> Why does this have to be in the common package?
I put it in the clients module since it's fairly generic and could be used in other places.
However, thinking about it more, maybe we should put it in the metadata module for now, to avoid adding more stuff to clients.
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569807496
##########
File path: metadata/src/main/java/org/apache/kafka/queue/EventQueue.java
##########
@@ -0,0 +1,232 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import org.slf4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+
+public interface EventQueue extends AutoCloseable {
+ interface Event {
+ void run() throws Exception;
+ default void handleException(Throwable e) {}
+ }
+
+ abstract class FailureLoggingEvent implements Event {
+ private final Logger log;
+
+ public FailureLoggingEvent(Logger log) {
+ this.log = log;
+ }
+
+ @Override
+ public void handleException(Throwable e) {
+ if (e instanceof EventQueueClosedException) {
+ log.info("Not processing {} because the event queue is closed.",
+ this.toString());
+ } else {
+ log.error("Unexpected error handling {}", this.toString(), e);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return this.getClass().getSimpleName();
+ }
+ }
+
+ class DeadlineFunction implements Function<Long, Long> {
+ private final long deadlineNs;
+
+ public DeadlineFunction(long deadlineNs) {
+ this.deadlineNs = deadlineNs;
+ }
+
+ @Override
+ public Long apply(Long t) {
+ return deadlineNs;
+ }
+ }
+
+ class EarliestDeadlineFunction implements Function<Long, Long> {
+ private final long newDeadlineNs;
+
+ public EarliestDeadlineFunction(long newDeadlineNs) {
+ this.newDeadlineNs = newDeadlineNs;
+ }
+
+ @Override
+ public Long apply(Long prevDeadlineNs) {
+ if (prevDeadlineNs == null) {
+ return newDeadlineNs;
+ } else if (prevDeadlineNs < newDeadlineNs) {
+ return prevDeadlineNs;
+ } else {
+ return newDeadlineNs;
+ }
+ }
+ }
+
+ class VoidEvent implements Event {
+ public final static VoidEvent INSTANCE = new VoidEvent();
+
+ @Override
+ public void run() throws Exception {
+ }
+ }
+
+ /**
+ * Add an element to the front of the queue.
+ *
+ * @param event The mandatory event to prepend.
+ */
+ default void prepend(Event event) {
+ enqueue(EventInsertionType.PREPEND, null, null, event);
+ }
+
+ /**
+ * Add an element to the end of the queue.
+ *
+ * @param event The event to append.
+ */
+ default void append(Event event) {
+ enqueue(EventInsertionType.APPEND, null, null, event);
+ }
+
+ /**
+ * Enqueue an event to be run in FIFO order.
+ *
+ * @param deadlineNs The time in monotonic nanoseconds after which the future
+ * is completed with a
+ * @{org.apache.kafka.common.errors.TimeoutException},
+ * and the event is cancelled.
Review comment:
Good question. I clarified this comment a bit.
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[GitHub] [kafka] cmccabe merged pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe merged pull request #10030:
URL: https://github.com/apache/kafka/pull/10030
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[GitHub] [kafka] cmccabe commented on a change in pull request #10030: MINOR: Add KafkaEventQueue
Posted by GitBox <gi...@apache.org>.
cmccabe commented on a change in pull request #10030:
URL: https://github.com/apache/kafka/pull/10030#discussion_r569824493
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
Review comment:
> Hmm. Does this mean that DEFERRED events cannot timeout?
yes
> How about making the two threshold described independently when the event is enqueued?
there's no use-case for timing out deferred events. they go to the head of the queue when their time arrives in any case.
##########
File path: metadata/src/main/java/org/apache/kafka/queue/KafkaEventQueue.java
##########
@@ -0,0 +1,420 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.kafka.queue;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
+import org.apache.kafka.common.errors.TimeoutException;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.common.utils.Time;
+import org.slf4j.Logger;
+
+
+public final class KafkaEventQueue implements EventQueue {
+ /**
+ * A context object that wraps events.
+ */
+ private static class EventContext {
+ /**
+ * The caller-supplied event.
+ */
+ private final Event event;
+
+ /**
+ * How this event was inserted.
+ */
+ private final EventInsertionType insertionType;
+
+ /**
+ * The previous pointer of our circular doubly-linked list.
+ */
+ private EventContext prev = this;
+
+ /**
+ * The next pointer in our circular doubly-linked list.
+ */
+ private EventContext next = this;
+
+ /**
+ * If this event is in the delay map, this is the key it is there under.
+ * If it is not in the map, this is null.
+ */
+ private Long deadlineNs = null;
+
+ /**
+ * The tag associated with this event.
+ */
+ private String tag;
+
+ EventContext(Event event, EventInsertionType insertionType, String tag) {
+ this.event = event;
+ this.insertionType = insertionType;
+ this.tag = tag;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list after this node.
+ */
+ void insertAfter(EventContext other) {
+ this.next.prev = other;
+ other.next = this.next;
+ other.prev = this;
+ this.next = other;
+ }
+
+ /**
+ * Insert a new node in the circularly linked list before this node.
+ */
+ void insertBefore(EventContext other) {
+ this.prev.next = other;
+ other.prev = this.prev;
+ other.next = this;
+ this.prev = other;
+ }
+
+ /**
+ * Remove this node from the circularly linked list.
+ */
+ void remove() {
+ this.prev.next = this.next;
+ this.next.prev = this.prev;
+ this.prev = this;
+ this.next = this;
+ }
+
+ /**
+ * Returns true if this node is the only element in its list.
+ */
+ boolean isSingleton() {
+ return prev == this && next == this;
+ }
+
+ /**
+ * Run the event associated with this EventContext.
+ */
+ void run() throws InterruptedException {
+ try {
+ event.run();
+ } catch (InterruptedException e) {
+ throw e;
+ } catch (Exception e) {
+ event.handleException(e);
+ }
+ }
+
+ /**
+ * Complete the event associated with this EventContext with a timeout exception.
+ */
+ void completeWithTimeout() {
+ completeWithException(new TimeoutException());
+ }
+
+ /**
+ * Complete the event associated with this EventContext with the specified
+ * exception.
+ */
+ void completeWithException(Throwable t) {
+ event.handleException(t);
+ }
+ }
+
+ private class EventHandler implements Runnable {
+ /**
+ * Event contexts indexed by tag. Events without a tag are not included here.
+ */
+ private final Map<String, EventContext> tagToEventContext = new HashMap<>();
+
+ /**
+ * The head of the event queue.
+ */
+ private final EventContext head = new EventContext(null, null, null);
+
+ /**
+ * An ordered map of times in monotonic nanoseconds to events to time out.
+ */
+ private final TreeMap<Long, EventContext> delayMap = new TreeMap<>();
+
+ /**
+ * A condition variable for waking up the event handler thread.
+ */
+ private final Condition cond = lock.newCondition();
+
+ @Override
+ public void run() {
+ try {
+ handleEvents();
+ cleanupEvent.run();
+ } catch (Throwable e) {
+ log.warn("event handler thread exiting with exception", e);
+ }
+ }
+
+ private void remove(EventContext eventContext) {
+ eventContext.remove();
+ if (eventContext.deadlineNs != null) {
+ delayMap.remove(eventContext.deadlineNs);
+ eventContext.deadlineNs = null;
+ }
+ if (eventContext.tag != null) {
+ tagToEventContext.remove(eventContext.tag, eventContext);
+ eventContext.tag = null;
+ }
+ }
+
+ private void handleEvents() throws InterruptedException {
+ EventContext toTimeout = null;
+ EventContext toRun = null;
+ while (true) {
+ if (toTimeout != null) {
+ toTimeout.completeWithTimeout();
+ toTimeout = null;
+ } else if (toRun != null) {
+ toRun.run();
+ toRun = null;
+ }
+ lock.lock();
+ try {
+ long awaitNs = Long.MAX_VALUE;
+ Map.Entry<Long, EventContext> entry = delayMap.firstEntry();
+ if (entry != null) {
+ // Search for timed-out events or deferred events that are ready
+ // to run.
+ long now = time.nanoseconds();
+ long timeoutNs = entry.getKey();
+ EventContext eventContext = entry.getValue();
+ if (timeoutNs <= now) {
+ if (eventContext.insertionType == EventInsertionType.DEFERRED) {
Review comment:
> Hmm. Does this mean that DEFERRED events cannot timeout?
yes
> How about making the two threshold described independently when the event is enqueued?
there's no use-case for timing out deferred events. they go to the head of the queue when their time arrives in any case.
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