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Posted to commits@kafka.apache.org by da...@apache.org on 2023/04/13 06:33:54 UTC
[kafka] branch trunk updated: KAFKA-14462; [5/N] Add EventAccumulator (#13505)
This is an automated email from the ASF dual-hosted git repository.
dajac pushed a commit to branch trunk
in repository https://gitbox.apache.org/repos/asf/kafka.git
The following commit(s) were added to refs/heads/trunk by this push:
new 440a53099d6 KAFKA-14462; [5/N] Add EventAccumulator (#13505)
440a53099d6 is described below
commit 440a53099d6aed34bc9f407b5fb3d74484f1e167
Author: David Jacot <dj...@confluent.io>
AuthorDate: Thu Apr 13 08:33:40 2023 +0200
KAFKA-14462; [5/N] Add EventAccumulator (#13505)
This patch adds the `EventAccumulator` which will be used in the runtime of the new group coordinator. The aim of this accumulator is to basically have a queue per __consumer_group partitions and to ensure that events addressed to the same partitions are not processed concurrently. The accumulator is generic so we could reuse it in different context.
Reviewers: Alexandre Dupriez <al...@gmail.com>, Justine Olshan <jo...@confluent.io>
---
.../group/runtime/EventAccumulator.java | 256 +++++++++++++++++++++
.../group/runtime/EventAccumulatorTest.java | 233 +++++++++++++++++++
2 files changed, 489 insertions(+)
diff --git a/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/runtime/EventAccumulator.java b/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/runtime/EventAccumulator.java
new file mode 100644
index 00000000000..6ffa018931b
--- /dev/null
+++ b/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/runtime/EventAccumulator.java
@@ -0,0 +1,256 @@
+/*
+ * 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.coordinator.group.runtime;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * A concurrent event accumulator which group events per key and ensure that only one
+ * event with a given key can't be processed concurrently.
+ *
+ * This class is threadsafe.
+ *
+ * @param <K> The type of the key of the event.
+ * @param <T> The type of the event itself. It implements the {{@link Event}} interface.
+ *
+ * There are a few examples about how to use it in the unit tests.
+ */
+public class EventAccumulator<K, T extends EventAccumulator.Event<K>> implements AutoCloseable {
+
+ /**
+ * The interface which must be implemented by all events.
+ *
+ * @param <K> The type of the key of the event.
+ */
+ public interface Event<K> {
+ K key();
+ }
+
+ /**
+ * The random generator used by this class.
+ */
+ private final Random random;
+
+ /**
+ * The map of queues keyed by K.
+ */
+ private final Map<K, Queue<T>> queues;
+
+ /**
+ * The list of available keys. Keys in this list can
+ * be delivered to pollers.
+ */
+ private final List<K> availableKeys;
+
+ /**
+ * The set of keys that are being processed.
+ */
+ private final Set<K> inflightKeys;
+
+ /**
+ * The lock for protecting access to the resources.
+ */
+ private final ReentrantLock lock;
+
+ /**
+ * The condition variable for waking up poller threads.
+ */
+ private final Condition condition;
+
+ /**
+ * The number of events in the accumulator.
+ */
+ private int size;
+
+ /**
+ * A boolean indicated whether the accumulator is closed.
+ */
+ private boolean closed;
+
+ public EventAccumulator() {
+ this(new Random());
+ }
+
+ public EventAccumulator(
+ Random random
+ ) {
+ this.random = random;
+ this.queues = new HashMap<>();
+ this.availableKeys = new ArrayList<>();
+ this.inflightKeys = new HashSet<>();
+ this.closed = false;
+ this.lock = new ReentrantLock();
+ this.condition = lock.newCondition();
+ }
+
+ /**
+ * Adds an {{@link Event}} to the queue.
+ *
+ * @param event An {{@link Event}}.
+ */
+ public void add(T event) {
+ lock.lock();
+ try {
+ if (closed) throw new IllegalStateException("Can't accept an event because the accumulator is closed.");
+
+ K key = event.key();
+ Queue<T> queue = queues.get(key);
+ if (queue == null) {
+ queue = new LinkedList<>();
+ queues.put(key, queue);
+ if (!inflightKeys.contains(key)) {
+ addAvailableKey(key);
+ }
+ }
+ queue.add(event);
+ size++;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Returns the next {{@link Event}} available. This method block indefinitely until
+ * one event is ready or the accumulator is closed.
+ *
+ * @return The next event.
+ */
+ public T poll() {
+ return poll(Long.MAX_VALUE, TimeUnit.SECONDS);
+ }
+
+ /**
+ * Returns the next {{@link Event}} available. This method blocks for the provided
+ * time and returns null of not event is available.
+ *
+ * @param timeout The timeout.
+ * @param unit The timeout unit.
+ * @return The next event available or null.
+ */
+ public T poll(long timeout, TimeUnit unit) {
+ lock.lock();
+ try {
+ K key = randomKey();
+ long nanos = unit.toNanos(timeout);
+ while (key == null && !closed && nanos > 0) {
+ try {
+ nanos = condition.awaitNanos(nanos);
+ } catch (InterruptedException e) {
+ // Ignore.
+ }
+ key = randomKey();
+ }
+
+ if (key == null) return null;
+
+ Queue<T> queue = queues.get(key);
+ T event = queue.poll();
+
+ if (queue.isEmpty()) queues.remove(key);
+ inflightKeys.add(key);
+ size--;
+
+ return event;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Marks the event as processed and releases the next event
+ * with the same key. This unblocks waiting threads.
+ *
+ * @param event The event that was processed.
+ */
+ public void done(T event) {
+ lock.lock();
+ try {
+ K key = event.key();
+ inflightKeys.remove(key);
+ if (queues.containsKey(key)) {
+ addAvailableKey(key);
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Returns the size of the accumulator.
+ */
+ public int size() {
+ lock.lock();
+ try {
+ return size;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Closes the accumulator. This unblocks all the waiting threads.
+ */
+ @Override
+ public void close() {
+ lock.lock();
+ try {
+ closed = true;
+ condition.signalAll();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Adds the key to the available keys set.
+ *
+ * This method must be called while holding the lock.
+ */
+ private void addAvailableKey(K key) {
+ availableKeys.add(key);
+ condition.signalAll();
+ }
+
+ /**
+ * Returns the next available key. The key is selected randomly
+ * from the available keys set.
+ *
+ * This method must be called while holding the lock.
+ */
+ private K randomKey() {
+ if (availableKeys.isEmpty()) return null;
+
+ int lastIndex = availableKeys.size() - 1;
+ int randomIndex = random.nextInt(availableKeys.size());
+ K randomKey = availableKeys.get(randomIndex);
+ Collections.swap(availableKeys, randomIndex, lastIndex);
+ availableKeys.remove(lastIndex);
+ return randomKey;
+ }
+}
diff --git a/group-coordinator/src/test/java/org/apache/kafka/coordinator/group/runtime/EventAccumulatorTest.java b/group-coordinator/src/test/java/org/apache/kafka/coordinator/group/runtime/EventAccumulatorTest.java
new file mode 100644
index 00000000000..f2524f83384
--- /dev/null
+++ b/group-coordinator/src/test/java/org/apache/kafka/coordinator/group/runtime/EventAccumulatorTest.java
@@ -0,0 +1,233 @@
+/*
+ * 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.coordinator.group.runtime;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+public class EventAccumulatorTest {
+
+ private class MockEvent implements EventAccumulator.Event<Integer> {
+ int key;
+ int value;
+
+ MockEvent(int key, int value) {
+ this.key = key;
+ this.value = value;
+ }
+
+ @Override
+ public Integer key() {
+ return key;
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o) return true;
+ if (o == null || getClass() != o.getClass()) return false;
+
+ MockEvent mockEvent = (MockEvent) o;
+
+ if (key != mockEvent.key) return false;
+ return value == mockEvent.value;
+ }
+
+ @Override
+ public int hashCode() {
+ int result = key;
+ result = 31 * result + value;
+ return result;
+ }
+
+ @Override
+ public String toString() {
+ return "MockEvent(key=" + key + ", value=" + value + ')';
+ }
+ }
+
+ @Test
+ public void testBasicOperations() {
+ EventAccumulator<Integer, MockEvent> accumulator = new EventAccumulator<>();
+
+ assertEquals(0, accumulator.size());
+ assertNull(accumulator.poll(0, TimeUnit.MICROSECONDS));
+
+ List<MockEvent> events = Arrays.asList(
+ new MockEvent(1, 0),
+ new MockEvent(1, 1),
+ new MockEvent(1, 2),
+ new MockEvent(2, 0),
+ new MockEvent(2, 1),
+ new MockEvent(2, 3),
+ new MockEvent(3, 0),
+ new MockEvent(3, 1),
+ new MockEvent(3, 2)
+ );
+
+ events.forEach(accumulator::add);
+ assertEquals(9, accumulator.size());
+
+ Set<MockEvent> polledEvents = new HashSet<>();
+ for (int i = 0; i < events.size(); i++) {
+ MockEvent event = accumulator.poll(0, TimeUnit.MICROSECONDS);
+ assertNotNull(event);
+ polledEvents.add(event);
+ assertEquals(events.size() - 1 - i, accumulator.size());
+ accumulator.done(event);
+ }
+
+ assertNull(accumulator.poll(0, TimeUnit.MICROSECONDS));
+ assertEquals(new HashSet<>(events), polledEvents);
+ assertEquals(0, accumulator.size());
+
+ accumulator.close();
+ }
+
+ @Test
+ public void testKeyConcurrentProcessingAndOrdering() {
+ EventAccumulator<Integer, MockEvent> accumulator = new EventAccumulator<>();
+
+ MockEvent event0 = new MockEvent(1, 0);
+ MockEvent event1 = new MockEvent(1, 1);
+ MockEvent event2 = new MockEvent(1, 2);
+ accumulator.add(event0);
+ accumulator.add(event1);
+ accumulator.add(event2);
+ assertEquals(3, accumulator.size());
+
+ MockEvent event = null;
+
+ // Poll event0.
+ event = accumulator.poll(0, TimeUnit.MICROSECONDS);
+ assertEquals(event0, event);
+
+ // Poll returns null because key is inflight.
+ assertNull(accumulator.poll(0, TimeUnit.MICROSECONDS));
+ accumulator.done(event);
+
+ // Poll event1.
+ event = accumulator.poll(0, TimeUnit.MICROSECONDS);
+ assertEquals(event1, event);
+
+ // Poll returns null because key is inflight.
+ assertNull(accumulator.poll(0, TimeUnit.MICROSECONDS));
+ accumulator.done(event);
+
+ // Poll event2.
+ event = accumulator.poll(0, TimeUnit.MICROSECONDS);
+ assertEquals(event2, event);
+
+ // Poll returns null because key is inflight.
+ assertNull(accumulator.poll(0, TimeUnit.MICROSECONDS));
+ accumulator.done(event);
+
+ accumulator.close();
+ }
+
+ @Test
+ public void testDoneUnblockWaitingThreads() throws ExecutionException, InterruptedException, TimeoutException {
+ EventAccumulator<Integer, MockEvent> accumulator = new EventAccumulator<>();
+
+ MockEvent event0 = new MockEvent(1, 0);
+ MockEvent event1 = new MockEvent(1, 1);
+ MockEvent event2 = new MockEvent(1, 2);
+
+ CompletableFuture<MockEvent> future0 = CompletableFuture.supplyAsync(accumulator::poll);
+ CompletableFuture<MockEvent> future1 = CompletableFuture.supplyAsync(accumulator::poll);
+ CompletableFuture<MockEvent> future2 = CompletableFuture.supplyAsync(accumulator::poll);
+ List<CompletableFuture<MockEvent>> futures = Arrays.asList(future0, future1, future2);
+
+ assertFalse(future0.isDone());
+ assertFalse(future1.isDone());
+ assertFalse(future2.isDone());
+
+ accumulator.add(event0);
+ accumulator.add(event1);
+ accumulator.add(event2);
+
+ // One future should be completed with event0.
+ assertEquals(event0, CompletableFuture
+ .anyOf(futures.toArray(new CompletableFuture[0]))
+ .get(5, TimeUnit.SECONDS));
+
+ futures = futures.stream().filter(future -> !future.isDone()).collect(Collectors.toList());
+ assertEquals(2, futures.size());
+
+ // Processing of event0 is done.
+ accumulator.done(event0);
+
+ // One future should be completed with event1.
+ assertEquals(event1, CompletableFuture
+ .anyOf(futures.toArray(new CompletableFuture[0]))
+ .get(5, TimeUnit.SECONDS));
+
+ futures = futures.stream().filter(future -> !future.isDone()).collect(Collectors.toList());
+ assertEquals(1, futures.size());
+
+ // Processing of event1 is done.
+ accumulator.done(event1);
+
+ // One future should be completed with event2.
+ assertEquals(event2, CompletableFuture
+ .anyOf(futures.toArray(new CompletableFuture[0]))
+ .get(5, TimeUnit.SECONDS));
+
+ futures = futures.stream().filter(future -> !future.isDone()).collect(Collectors.toList());
+ assertEquals(0, futures.size());
+
+ // Processing of event2 is done.
+ accumulator.done(event2);
+
+ assertEquals(0, accumulator.size());
+
+ accumulator.close();
+ }
+
+ @Test
+ public void testCloseUnblockWaitingThreads() throws ExecutionException, InterruptedException, TimeoutException {
+ EventAccumulator<Integer, MockEvent> accumulator = new EventAccumulator<>();
+
+ CompletableFuture<MockEvent> future0 = CompletableFuture.supplyAsync(accumulator::poll);
+ CompletableFuture<MockEvent> future1 = CompletableFuture.supplyAsync(accumulator::poll);
+ CompletableFuture<MockEvent> future2 = CompletableFuture.supplyAsync(accumulator::poll);
+
+ assertFalse(future0.isDone());
+ assertFalse(future1.isDone());
+ assertFalse(future2.isDone());
+
+ // Closing should release all the pending futures.
+ accumulator.close();
+
+ assertNull(future0.get(5, TimeUnit.SECONDS));
+ assertNull(future1.get(5, TimeUnit.SECONDS));
+ assertNull(future2.get(5, TimeUnit.SECONDS));
+ }
+}