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Posted to jira@kafka.apache.org by "ijuma (via GitHub)" <gi...@apache.org> on 2023/02/02 13:53:40 UTC
[GitHub] [kafka] ijuma commented on a diff in pull request #13046: KAFKA-14551 Move/Rewrite LeaderEpochFileCache and its dependencies to the storage module.
ijuma commented on code in PR #13046:
URL: https://github.com/apache/kafka/pull/13046#discussion_r1080718765
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
+ return lastEntry.map(epochEntry -> entry.epoch != epochEntry.epoch || entry.startOffset < epochEntry.startOffset).orElse(true);
+ }
+
+ private boolean assign(EpochEntry entry) {
+ if (entry.epoch < 0 || entry.startOffset < 0) {
+ throw new IllegalArgumentException("Received invalid partition leader epoch entry " + entry);
+ }
+
+ // Check whether the append is needed before acquiring the write lock
+ // in order to avoid contention with readers in the common case
+ if (!isUpdateNeeded(entry)) return false;
+
+ lock.writeLock().lock();
+ try {
+ if (isUpdateNeeded(entry)) {
+ maybeTruncateNonMonotonicEntries(entry);
+ epochs.put(entry.epoch, entry);
+ return true;
+ } else {
+ return false;
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Remove any entries which violate monotonicity prior to appending a new entry
+ */
+ public void maybeTruncateNonMonotonicEntries(EpochEntry newEntry) {
+ List<EpochEntry> removedEpochs = removeFromEnd(entry -> entry.epoch >= newEntry.epoch || entry.startOffset >= newEntry.startOffset);
+
+
+ if (removedEpochs.size() > 1 || (!removedEpochs.isEmpty() && removedEpochs.get(0).startOffset != newEntry.startOffset)) {
+
+ // Only log a warning if there were non-trivial removals. If the start offset of the new entry
+ // matches the start offset of the removed epoch, then no data has been written and the truncation
+ // is expected.
+ log.warn("New epoch entry {} caused truncation of conflicting entries {}. " + "Cache now contains {} entries.", newEntry, removedEpochs, epochs.size());
+ }
+ }
+
+ private List<EpochEntry> removeFromEnd(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.descendingMap().entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeFromStart(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeWhileMatching(Iterator<Map.Entry<Integer, EpochEntry>> iterator, Predicate<EpochEntry> predicate) {
+ ArrayList<EpochEntry> removedEpochs = new ArrayList<>();
+
+ while (iterator.hasNext()) {
+ EpochEntry entry = iterator.next().getValue();
+ if (predicate.test(entry)) {
+ removedEpochs.add(entry);
+ iterator.remove();
+ } else {
+ return removedEpochs;
+ }
+ }
+
+ return removedEpochs;
+ }
+
+ public boolean nonEmpty() {
+ lock.readLock().lock();
+ try {
+ return !epochs.isEmpty();
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public Optional<EpochEntry> latestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.lastEntry()).map(Map.Entry::getValue);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the current Leader Epoch if one exists. This is the latest epoch
+ * which has messages assigned to it.
+ */
+ public Optional<Integer> latestEpoch() {
Review Comment:
Should this and `previousEpoch` be `OptionalInt`?
##########
core/src/main/scala/kafka/server/checkpoints/OffsetCheckpointFile.scala:
##########
@@ -65,9 +65,14 @@ class OffsetCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureCh
val checkpoint = new CheckpointFileWithFailureHandler[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
- def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets)
+ def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets.toSeq.asJava)
- def read(): Map[TopicPartition, Long] = checkpoint.read().toMap
+ def read(): Map[TopicPartition, Long] = {
+ val list = checkpoint.read()
+ val result = mutable.Map.empty[TopicPartition, Long]
+ list.forEach { case (tp, offset) => result += tp -> offset }
+ result.toMap
Review Comment:
Can we avoid the conversion to an immutable map here? The additional copy doesn't buy us anything.
##########
storage/src/main/java/org/apache/kafka/storage/internals/checkpoint/LeaderEpochCheckpointFile.java:
##########
@@ -0,0 +1,83 @@
+/*
+ * 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.storage.internals.checkpoint;
+
+import org.apache.kafka.server.common.CheckpointFile.EntryFormatter;
+import org.apache.kafka.server.log.internals.CheckpointFileWithFailureHandler;
+import org.apache.kafka.server.log.internals.EpochEntry;
+import org.apache.kafka.server.log.internals.LogDirFailureChannel;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import java.util.regex.Pattern;
+
+/**
+ * This class persists a map of (LeaderEpoch => Offsets) to a file (for a certain replica)
+ * <p>
+ * The format in the LeaderEpoch checkpoint file is like this:
+ * -----checkpoint file begin------
+ * 0 <- LeaderEpochCheckpointFile.currentVersion
+ * 2 <- following entries size
+ * 0 1 <- the format is: leader_epoch(int32) start_offset(int64)
+ * 1 2
+ * -----checkpoint file end----------
+ */
+public class LeaderEpochCheckpointFile implements LeaderEpochCheckpoint {
+
+ public static final Formatter FORMATTER = new Formatter();
+
+ private static final String LEADER_EPOCH_CHECKPOINT_FILENAME = "leader-epoch-checkpoint";
+ private static final Pattern WHITE_SPACES_PATTERN = Pattern.compile("\\s+");
+ private static final int CURRENT_VERSION = 0;
+
+ private final CheckpointFileWithFailureHandler<EpochEntry> checkpoint;
+
+ public LeaderEpochCheckpointFile(File file, LogDirFailureChannel logDirFailureChannel) throws IOException {
+ checkpoint = new CheckpointFileWithFailureHandler<>(file, CURRENT_VERSION, FORMATTER, logDirFailureChannel, file.getParentFile().getParent());
+ }
+
+ public LeaderEpochCheckpointFile(File file) throws IOException {
+ this(file, null);
+ }
+
+ public void write(Collection<EpochEntry> epochs) {
+ checkpoint.write(epochs);
+ }
+
+ public List<EpochEntry> read() {
+ return checkpoint.read();
+ }
+
+ public static File newFile(File dir) {
+ return new File(dir, LEADER_EPOCH_CHECKPOINT_FILENAME);
+ }
+
+ public static class Formatter implements EntryFormatter<EpochEntry> {
Review Comment:
Does this need to be public?
##########
core/src/main/scala/kafka/log/LogSegment.scala:
##########
@@ -249,9 +248,10 @@ class LogSegment private[log] (val log: FileRecords,
if (batch.hasProducerId) {
val producerId = batch.producerId
val appendInfo = producerStateManager.prepareUpdate(producerId, origin = AppendOrigin.REPLICATION)
- val maybeCompletedTxn = appendInfo.append(batch, Optional.empty()).asScala
+ val maybeCompletedTxn = appendInfo.append(batch, Optional.empty())
producerStateManager.update(appendInfo)
- maybeCompletedTxn.foreach { completedTxn =>
+ if (maybeCompletedTxn.isPresent) {
Review Comment:
Nit: `ifPresent` is the equivalent to `foreach`.
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
+ return lastEntry.map(epochEntry -> entry.epoch != epochEntry.epoch || entry.startOffset < epochEntry.startOffset).orElse(true);
+ }
+
+ private boolean assign(EpochEntry entry) {
+ if (entry.epoch < 0 || entry.startOffset < 0) {
+ throw new IllegalArgumentException("Received invalid partition leader epoch entry " + entry);
+ }
+
+ // Check whether the append is needed before acquiring the write lock
+ // in order to avoid contention with readers in the common case
+ if (!isUpdateNeeded(entry)) return false;
+
+ lock.writeLock().lock();
+ try {
+ if (isUpdateNeeded(entry)) {
+ maybeTruncateNonMonotonicEntries(entry);
+ epochs.put(entry.epoch, entry);
+ return true;
+ } else {
+ return false;
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Remove any entries which violate monotonicity prior to appending a new entry
+ */
+ public void maybeTruncateNonMonotonicEntries(EpochEntry newEntry) {
Review Comment:
This was private before, why is it now public?
##########
core/src/main/scala/kafka/server/checkpoints/OffsetCheckpointFile.scala:
##########
@@ -65,9 +65,14 @@ class OffsetCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureCh
val checkpoint = new CheckpointFileWithFailureHandler[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
- def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets)
+ def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets.toSeq.asJava)
Review Comment:
Is this `toSeq` call still required?
##########
core/src/main/scala/kafka/server/checkpoints/OffsetCheckpointFile.scala:
##########
@@ -65,9 +65,14 @@ class OffsetCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureCh
val checkpoint = new CheckpointFileWithFailureHandler[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
- def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets)
+ def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets.toSeq.asJava)
- def read(): Map[TopicPartition, Long] = checkpoint.read().toMap
+ def read(): Map[TopicPartition, Long] = {
+ val list = checkpoint.read()
+ val result = mutable.Map.empty[TopicPartition, Long]
Review Comment:
We should size the map appropriately.
##########
core/src/main/scala/kafka/server/checkpoints/OffsetCheckpointFile.scala:
##########
@@ -65,9 +65,14 @@ class OffsetCheckpointFile(val file: File, logDirFailureChannel: LogDirFailureCh
val checkpoint = new CheckpointFileWithFailureHandler[(TopicPartition, Long)](file, OffsetCheckpointFile.CurrentVersion,
OffsetCheckpointFile.Formatter, logDirFailureChannel, file.getParent)
- def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets)
+ def write(offsets: Map[TopicPartition, Long]): Unit = checkpoint.write(offsets.toSeq.asJava)
- def read(): Map[TopicPartition, Long] = checkpoint.read().toMap
+ def read(): Map[TopicPartition, Long] = {
+ val list = checkpoint.read()
+ val result = mutable.Map.empty[TopicPartition, Long]
+ list.forEach { case (tp, offset) => result += tp -> offset }
Review Comment:
You can avoid the tuple creation by using something like:
`result(tp) = offset`
##########
storage/src/main/java/org/apache/kafka/server/log/internals/CheckpointFileWithFailureHandler.java:
##########
@@ -0,0 +1,62 @@
+/*
+ * 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.server.log.internals;
Review Comment:
Why is this not in the checkpoint package?
##########
storage/src/main/java/org/apache/kafka/server/log/internals/EpochEntry.java:
##########
@@ -0,0 +1,51 @@
+/*
+ * 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.server.log.internals;
Review Comment:
This was previously under the `epoch` package. Should we do the same, i.e. `storage.internals.epoch`? Same for `LeaderEpochFileCache`.
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
Review Comment:
The original code did this under a write lock. Did we establish that it wasn't required?
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
Review Comment:
Nit: can this be inlined?
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
+ return lastEntry.map(epochEntry -> entry.epoch != epochEntry.epoch || entry.startOffset < epochEntry.startOffset).orElse(true);
+ }
+
+ private boolean assign(EpochEntry entry) {
+ if (entry.epoch < 0 || entry.startOffset < 0) {
+ throw new IllegalArgumentException("Received invalid partition leader epoch entry " + entry);
+ }
+
+ // Check whether the append is needed before acquiring the write lock
+ // in order to avoid contention with readers in the common case
+ if (!isUpdateNeeded(entry)) return false;
+
+ lock.writeLock().lock();
+ try {
+ if (isUpdateNeeded(entry)) {
+ maybeTruncateNonMonotonicEntries(entry);
+ epochs.put(entry.epoch, entry);
+ return true;
+ } else {
+ return false;
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Remove any entries which violate monotonicity prior to appending a new entry
+ */
+ public void maybeTruncateNonMonotonicEntries(EpochEntry newEntry) {
+ List<EpochEntry> removedEpochs = removeFromEnd(entry -> entry.epoch >= newEntry.epoch || entry.startOffset >= newEntry.startOffset);
+
+
+ if (removedEpochs.size() > 1 || (!removedEpochs.isEmpty() && removedEpochs.get(0).startOffset != newEntry.startOffset)) {
+
+ // Only log a warning if there were non-trivial removals. If the start offset of the new entry
+ // matches the start offset of the removed epoch, then no data has been written and the truncation
+ // is expected.
+ log.warn("New epoch entry {} caused truncation of conflicting entries {}. " + "Cache now contains {} entries.", newEntry, removedEpochs, epochs.size());
+ }
+ }
+
+ private List<EpochEntry> removeFromEnd(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.descendingMap().entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeFromStart(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeWhileMatching(Iterator<Map.Entry<Integer, EpochEntry>> iterator, Predicate<EpochEntry> predicate) {
+ ArrayList<EpochEntry> removedEpochs = new ArrayList<>();
+
+ while (iterator.hasNext()) {
+ EpochEntry entry = iterator.next().getValue();
+ if (predicate.test(entry)) {
+ removedEpochs.add(entry);
+ iterator.remove();
+ } else {
+ return removedEpochs;
+ }
+ }
+
+ return removedEpochs;
+ }
+
+ public boolean nonEmpty() {
+ lock.readLock().lock();
+ try {
+ return !epochs.isEmpty();
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public Optional<EpochEntry> latestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.lastEntry()).map(Map.Entry::getValue);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the current Leader Epoch if one exists. This is the latest epoch
+ * which has messages assigned to it.
+ */
+ public Optional<Integer> latestEpoch() {
+ return latestEntry().map(x -> x.epoch);
+ }
+
+ public Optional<Integer> previousEpoch() {
+ lock.readLock().lock();
+ try {
+ return latestEntry().flatMap(entry -> Optional.ofNullable(epochs.lowerEntry(entry.epoch))).map(Map.Entry::getKey);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Get the earliest cached entry if one exists.
+ */
+ public Optional<EpochEntry> earliestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.firstEntry()).map(x -> x.getValue());
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt previousEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.lowerKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt nextEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.higherKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ private static OptionalInt toOptionalInt(Integer value) {
+ return (value != null) ? OptionalInt.of(value) : OptionalInt.empty();
+ }
+
+ public Optional<EpochEntry> epochEntry(int epoch) {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.get(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the Leader Epoch and the End Offset for a requested Leader Epoch.
+ * <p>
+ * The Leader Epoch returned is the largest epoch less than or equal to the requested Leader
+ * Epoch. The End Offset is the end offset of this epoch, which is defined as the start offset
+ * of the first Leader Epoch larger than the Leader Epoch requested, or else the Log End
+ * Offset if the latest epoch was requested.
+ * <p>
+ * During the upgrade phase, where there are existing messages may not have a leader epoch,
+ * if requestedEpoch is < the first epoch cached, UNDEFINED_EPOCH_OFFSET will be returned
+ * so that the follower falls back to High Water Mark.
+ *
+ * @param requestedEpoch requested leader epoch
+ * @param logEndOffset the existing Log End Offset
+ * @return found leader epoch and end offset
+ */
+ public Map.Entry<Integer, Long> endOffsetFor(int requestedEpoch, long logEndOffset) {
+ lock.readLock().lock();
+ try {
+ Map.Entry<Integer, Long> epochAndOffset = null;
+ if (requestedEpoch == UNDEFINED_EPOCH) {
+ // This may happen if a bootstrapping follower sends a request with undefined epoch or
+ // a follower is on the older message format where leader epochs are not recorded
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else if (latestEpoch().isPresent() && latestEpoch().get() == requestedEpoch) {
+ // For the leader, the latest epoch is always the current leader epoch that is still being written to.
+ // Followers should not have any reason to query for the end offset of the current epoch, but a consumer
+ // might if it is verifying its committed offset following a group rebalance. In this case, we return
+ // the current log end offset which makes the truncation check work as expected.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, logEndOffset);
+ } else {
+ Map.Entry<Integer, EpochEntry> higherEntry = epochs.higherEntry(requestedEpoch);
+ if (higherEntry == null) {
+ // The requested epoch is larger than any known epoch. This case should never be hit because
+ // the latest cached epoch is always the largest.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else {
+ Map.Entry<Integer, EpochEntry> floorEntry = epochs.floorEntry(requestedEpoch);
+ if (floorEntry == null) {
+ // The requested epoch is smaller than any known epoch, so we return the start offset of the first
+ // known epoch which is larger than it. This may be inaccurate as there could have been
+ // epochs in between, but the point is that the data has already been removed from the log
+ // and we want to ensure that the follower can replicate correctly beginning from the leader's
+ // start offset.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, higherEntry.getValue().startOffset);
+ } else {
+ // We have at least one previous epoch and one subsequent epoch. The result is the first
+ // prior epoch and the starting offset of the first subsequent epoch.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(floorEntry.getValue().epoch, higherEntry.getValue().startOffset);
+ }
+ }
+ }
+ log.trace("Processed end offset request for epoch {} and returning epoch {} " + "with end offset {} from epoch cache of size {}}", requestedEpoch, epochAndOffset.getKey(), epochAndOffset.getValue(), epochs.size());
+ return epochAndOffset;
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Removes all epoch entries from the store with start offsets greater than or equal to the passed offset.
+ */
+ public void truncateFromEnd(long endOffset) {
+ lock.writeLock().lock();
+ try {
+ Optional<EpochEntry> epochEntry = latestEntry();
+ if (endOffset >= 0 && epochEntry.isPresent() && epochEntry.get().startOffset >= endOffset) {
+ List<EpochEntry> removedEntries = removeFromEnd(x -> x.startOffset >= endOffset);
+
+ flush();
+
+ log.debug("Cleared entries {} from epoch cache after " + "truncating to end offset {}, leaving {} entries in the cache.", removedEntries, endOffset, epochs.size());
Review Comment:
No need for string concat here.
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
+ return lastEntry.map(epochEntry -> entry.epoch != epochEntry.epoch || entry.startOffset < epochEntry.startOffset).orElse(true);
+ }
+
+ private boolean assign(EpochEntry entry) {
+ if (entry.epoch < 0 || entry.startOffset < 0) {
+ throw new IllegalArgumentException("Received invalid partition leader epoch entry " + entry);
+ }
+
+ // Check whether the append is needed before acquiring the write lock
+ // in order to avoid contention with readers in the common case
+ if (!isUpdateNeeded(entry)) return false;
+
+ lock.writeLock().lock();
+ try {
+ if (isUpdateNeeded(entry)) {
+ maybeTruncateNonMonotonicEntries(entry);
+ epochs.put(entry.epoch, entry);
+ return true;
+ } else {
+ return false;
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Remove any entries which violate monotonicity prior to appending a new entry
+ */
+ public void maybeTruncateNonMonotonicEntries(EpochEntry newEntry) {
+ List<EpochEntry> removedEpochs = removeFromEnd(entry -> entry.epoch >= newEntry.epoch || entry.startOffset >= newEntry.startOffset);
+
+
+ if (removedEpochs.size() > 1 || (!removedEpochs.isEmpty() && removedEpochs.get(0).startOffset != newEntry.startOffset)) {
+
+ // Only log a warning if there were non-trivial removals. If the start offset of the new entry
+ // matches the start offset of the removed epoch, then no data has been written and the truncation
+ // is expected.
+ log.warn("New epoch entry {} caused truncation of conflicting entries {}. " + "Cache now contains {} entries.", newEntry, removedEpochs, epochs.size());
+ }
+ }
+
+ private List<EpochEntry> removeFromEnd(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.descendingMap().entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeFromStart(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeWhileMatching(Iterator<Map.Entry<Integer, EpochEntry>> iterator, Predicate<EpochEntry> predicate) {
+ ArrayList<EpochEntry> removedEpochs = new ArrayList<>();
+
+ while (iterator.hasNext()) {
+ EpochEntry entry = iterator.next().getValue();
+ if (predicate.test(entry)) {
+ removedEpochs.add(entry);
+ iterator.remove();
+ } else {
+ return removedEpochs;
+ }
+ }
+
+ return removedEpochs;
+ }
+
+ public boolean nonEmpty() {
+ lock.readLock().lock();
+ try {
+ return !epochs.isEmpty();
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public Optional<EpochEntry> latestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.lastEntry()).map(Map.Entry::getValue);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the current Leader Epoch if one exists. This is the latest epoch
+ * which has messages assigned to it.
+ */
+ public Optional<Integer> latestEpoch() {
+ return latestEntry().map(x -> x.epoch);
+ }
+
+ public Optional<Integer> previousEpoch() {
+ lock.readLock().lock();
+ try {
+ return latestEntry().flatMap(entry -> Optional.ofNullable(epochs.lowerEntry(entry.epoch))).map(Map.Entry::getKey);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Get the earliest cached entry if one exists.
+ */
+ public Optional<EpochEntry> earliestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.firstEntry()).map(x -> x.getValue());
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt previousEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.lowerKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt nextEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.higherKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ private static OptionalInt toOptionalInt(Integer value) {
+ return (value != null) ? OptionalInt.of(value) : OptionalInt.empty();
+ }
+
+ public Optional<EpochEntry> epochEntry(int epoch) {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.get(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the Leader Epoch and the End Offset for a requested Leader Epoch.
+ * <p>
+ * The Leader Epoch returned is the largest epoch less than or equal to the requested Leader
+ * Epoch. The End Offset is the end offset of this epoch, which is defined as the start offset
+ * of the first Leader Epoch larger than the Leader Epoch requested, or else the Log End
+ * Offset if the latest epoch was requested.
+ * <p>
+ * During the upgrade phase, where there are existing messages may not have a leader epoch,
+ * if requestedEpoch is < the first epoch cached, UNDEFINED_EPOCH_OFFSET will be returned
+ * so that the follower falls back to High Water Mark.
+ *
+ * @param requestedEpoch requested leader epoch
+ * @param logEndOffset the existing Log End Offset
+ * @return found leader epoch and end offset
+ */
+ public Map.Entry<Integer, Long> endOffsetFor(int requestedEpoch, long logEndOffset) {
+ lock.readLock().lock();
+ try {
+ Map.Entry<Integer, Long> epochAndOffset = null;
+ if (requestedEpoch == UNDEFINED_EPOCH) {
+ // This may happen if a bootstrapping follower sends a request with undefined epoch or
+ // a follower is on the older message format where leader epochs are not recorded
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else if (latestEpoch().isPresent() && latestEpoch().get() == requestedEpoch) {
+ // For the leader, the latest epoch is always the current leader epoch that is still being written to.
+ // Followers should not have any reason to query for the end offset of the current epoch, but a consumer
+ // might if it is verifying its committed offset following a group rebalance. In this case, we return
+ // the current log end offset which makes the truncation check work as expected.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, logEndOffset);
+ } else {
+ Map.Entry<Integer, EpochEntry> higherEntry = epochs.higherEntry(requestedEpoch);
+ if (higherEntry == null) {
+ // The requested epoch is larger than any known epoch. This case should never be hit because
+ // the latest cached epoch is always the largest.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else {
+ Map.Entry<Integer, EpochEntry> floorEntry = epochs.floorEntry(requestedEpoch);
+ if (floorEntry == null) {
+ // The requested epoch is smaller than any known epoch, so we return the start offset of the first
+ // known epoch which is larger than it. This may be inaccurate as there could have been
+ // epochs in between, but the point is that the data has already been removed from the log
+ // and we want to ensure that the follower can replicate correctly beginning from the leader's
+ // start offset.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, higherEntry.getValue().startOffset);
+ } else {
+ // We have at least one previous epoch and one subsequent epoch. The result is the first
+ // prior epoch and the starting offset of the first subsequent epoch.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(floorEntry.getValue().epoch, higherEntry.getValue().startOffset);
+ }
+ }
+ }
+ log.trace("Processed end offset request for epoch {} and returning epoch {} " + "with end offset {} from epoch cache of size {}}", requestedEpoch, epochAndOffset.getKey(), epochAndOffset.getValue(), epochs.size());
+ return epochAndOffset;
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Removes all epoch entries from the store with start offsets greater than or equal to the passed offset.
+ */
+ public void truncateFromEnd(long endOffset) {
+ lock.writeLock().lock();
+ try {
+ Optional<EpochEntry> epochEntry = latestEntry();
+ if (endOffset >= 0 && epochEntry.isPresent() && epochEntry.get().startOffset >= endOffset) {
+ List<EpochEntry> removedEntries = removeFromEnd(x -> x.startOffset >= endOffset);
+
+ flush();
+
+ log.debug("Cleared entries {} from epoch cache after " + "truncating to end offset {}, leaving {} entries in the cache.", removedEntries, endOffset, epochs.size());
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Clears old epoch entries. This method searches for the oldest epoch < offset, updates the saved epoch offset to
+ * be offset, then clears any previous epoch entries.
+ * <p>
+ * This method is exclusive: so truncateFromStart(6) will retain an entry at offset 6.
+ *
+ * @param startOffset the offset to clear up to
+ */
+ public void truncateFromStart(long startOffset) {
+ lock.writeLock().lock();
+ try {
+ List<EpochEntry> removedEntries = removeFromStart(entry -> entry.startOffset <= startOffset);
+
+ EpochEntry firstBeforeStartOffset;
Review Comment:
Why do we need this before the `if`?
##########
storage/src/main/java/org/apache/kafka/server/log/internals/LeaderEpochFileCache.java:
##########
@@ -0,0 +1,385 @@
+/*
+ * 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.server.log.internals;
+
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.storage.internals.checkpoint.LeaderEpochCheckpoint;
+import org.slf4j.Logger;
+
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalInt;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.function.Predicate;
+
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH;
+import static org.apache.kafka.common.requests.OffsetsForLeaderEpochResponse.UNDEFINED_EPOCH_OFFSET;
+
+/**
+ * Represents a cache of (LeaderEpoch => Offset) mappings for a particular replica.
+ * <p>
+ * Leader Epoch = epoch assigned to each leader by the controller.
+ * Offset = offset of the first message in each epoch.
+ */
+public class LeaderEpochFileCache {
+ private final LeaderEpochCheckpoint checkpoint;
+ private final Logger log;
+
+ private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+ private final TreeMap<Integer, EpochEntry> epochs = new TreeMap<>();
+
+ /**
+ * @param topicPartition the associated topic partition
+ * @param checkpoint the checkpoint file
+ */
+ public LeaderEpochFileCache(TopicPartition topicPartition, LeaderEpochCheckpoint checkpoint) {
+ this.checkpoint = checkpoint;
+ LogContext logContext = new LogContext("[LeaderEpochCache " + topicPartition + "] ");
+ log = logContext.logger(LeaderEpochFileCache.class);
+ checkpoint.read().forEach(this::assign);
+ }
+
+ /**
+ * Assigns the supplied Leader Epoch to the supplied Offset
+ * Once the epoch is assigned it cannot be reassigned
+ */
+ public void assign(int epoch, long startOffset) {
+ EpochEntry entry = new EpochEntry(epoch, startOffset);
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ flush();
+ }
+ }
+
+ public void assign(List<EpochEntry> entries) {
+ entries.forEach(entry -> {
+ if (assign(entry)) {
+ log.debug("Appended new epoch entry {}. Cache now contains {} entries.", entry, epochs.size());
+ }
+ });
+ flush();
+ }
+
+ private boolean isUpdateNeeded(EpochEntry entry) {
+ Optional<EpochEntry> lastEntry = latestEntry();
+ return lastEntry.map(epochEntry -> entry.epoch != epochEntry.epoch || entry.startOffset < epochEntry.startOffset).orElse(true);
+ }
+
+ private boolean assign(EpochEntry entry) {
+ if (entry.epoch < 0 || entry.startOffset < 0) {
+ throw new IllegalArgumentException("Received invalid partition leader epoch entry " + entry);
+ }
+
+ // Check whether the append is needed before acquiring the write lock
+ // in order to avoid contention with readers in the common case
+ if (!isUpdateNeeded(entry)) return false;
+
+ lock.writeLock().lock();
+ try {
+ if (isUpdateNeeded(entry)) {
+ maybeTruncateNonMonotonicEntries(entry);
+ epochs.put(entry.epoch, entry);
+ return true;
+ } else {
+ return false;
+ }
+ } finally {
+ lock.writeLock().unlock();
+ }
+ }
+
+ /**
+ * Remove any entries which violate monotonicity prior to appending a new entry
+ */
+ public void maybeTruncateNonMonotonicEntries(EpochEntry newEntry) {
+ List<EpochEntry> removedEpochs = removeFromEnd(entry -> entry.epoch >= newEntry.epoch || entry.startOffset >= newEntry.startOffset);
+
+
+ if (removedEpochs.size() > 1 || (!removedEpochs.isEmpty() && removedEpochs.get(0).startOffset != newEntry.startOffset)) {
+
+ // Only log a warning if there were non-trivial removals. If the start offset of the new entry
+ // matches the start offset of the removed epoch, then no data has been written and the truncation
+ // is expected.
+ log.warn("New epoch entry {} caused truncation of conflicting entries {}. " + "Cache now contains {} entries.", newEntry, removedEpochs, epochs.size());
+ }
+ }
+
+ private List<EpochEntry> removeFromEnd(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.descendingMap().entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeFromStart(Predicate<EpochEntry> predicate) {
+ return removeWhileMatching(epochs.entrySet().iterator(), predicate);
+ }
+
+ private List<EpochEntry> removeWhileMatching(Iterator<Map.Entry<Integer, EpochEntry>> iterator, Predicate<EpochEntry> predicate) {
+ ArrayList<EpochEntry> removedEpochs = new ArrayList<>();
+
+ while (iterator.hasNext()) {
+ EpochEntry entry = iterator.next().getValue();
+ if (predicate.test(entry)) {
+ removedEpochs.add(entry);
+ iterator.remove();
+ } else {
+ return removedEpochs;
+ }
+ }
+
+ return removedEpochs;
+ }
+
+ public boolean nonEmpty() {
+ lock.readLock().lock();
+ try {
+ return !epochs.isEmpty();
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public Optional<EpochEntry> latestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.lastEntry()).map(Map.Entry::getValue);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the current Leader Epoch if one exists. This is the latest epoch
+ * which has messages assigned to it.
+ */
+ public Optional<Integer> latestEpoch() {
+ return latestEntry().map(x -> x.epoch);
+ }
+
+ public Optional<Integer> previousEpoch() {
+ lock.readLock().lock();
+ try {
+ return latestEntry().flatMap(entry -> Optional.ofNullable(epochs.lowerEntry(entry.epoch))).map(Map.Entry::getKey);
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Get the earliest cached entry if one exists.
+ */
+ public Optional<EpochEntry> earliestEntry() {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.firstEntry()).map(x -> x.getValue());
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt previousEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.lowerKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ public OptionalInt nextEpoch(int epoch) {
+ lock.readLock().lock();
+ try {
+ return toOptionalInt(epochs.higherKey(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ private static OptionalInt toOptionalInt(Integer value) {
+ return (value != null) ? OptionalInt.of(value) : OptionalInt.empty();
+ }
+
+ public Optional<EpochEntry> epochEntry(int epoch) {
+ lock.readLock().lock();
+ try {
+ return Optional.ofNullable(epochs.get(epoch));
+ } finally {
+ lock.readLock().unlock();
+ }
+ }
+
+ /**
+ * Returns the Leader Epoch and the End Offset for a requested Leader Epoch.
+ * <p>
+ * The Leader Epoch returned is the largest epoch less than or equal to the requested Leader
+ * Epoch. The End Offset is the end offset of this epoch, which is defined as the start offset
+ * of the first Leader Epoch larger than the Leader Epoch requested, or else the Log End
+ * Offset if the latest epoch was requested.
+ * <p>
+ * During the upgrade phase, where there are existing messages may not have a leader epoch,
+ * if requestedEpoch is < the first epoch cached, UNDEFINED_EPOCH_OFFSET will be returned
+ * so that the follower falls back to High Water Mark.
+ *
+ * @param requestedEpoch requested leader epoch
+ * @param logEndOffset the existing Log End Offset
+ * @return found leader epoch and end offset
+ */
+ public Map.Entry<Integer, Long> endOffsetFor(int requestedEpoch, long logEndOffset) {
+ lock.readLock().lock();
+ try {
+ Map.Entry<Integer, Long> epochAndOffset = null;
+ if (requestedEpoch == UNDEFINED_EPOCH) {
+ // This may happen if a bootstrapping follower sends a request with undefined epoch or
+ // a follower is on the older message format where leader epochs are not recorded
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else if (latestEpoch().isPresent() && latestEpoch().get() == requestedEpoch) {
+ // For the leader, the latest epoch is always the current leader epoch that is still being written to.
+ // Followers should not have any reason to query for the end offset of the current epoch, but a consumer
+ // might if it is verifying its committed offset following a group rebalance. In this case, we return
+ // the current log end offset which makes the truncation check work as expected.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, logEndOffset);
+ } else {
+ Map.Entry<Integer, EpochEntry> higherEntry = epochs.higherEntry(requestedEpoch);
+ if (higherEntry == null) {
+ // The requested epoch is larger than any known epoch. This case should never be hit because
+ // the latest cached epoch is always the largest.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(UNDEFINED_EPOCH, UNDEFINED_EPOCH_OFFSET);
+ } else {
+ Map.Entry<Integer, EpochEntry> floorEntry = epochs.floorEntry(requestedEpoch);
+ if (floorEntry == null) {
+ // The requested epoch is smaller than any known epoch, so we return the start offset of the first
+ // known epoch which is larger than it. This may be inaccurate as there could have been
+ // epochs in between, but the point is that the data has already been removed from the log
+ // and we want to ensure that the follower can replicate correctly beginning from the leader's
+ // start offset.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(requestedEpoch, higherEntry.getValue().startOffset);
+ } else {
+ // We have at least one previous epoch and one subsequent epoch. The result is the first
+ // prior epoch and the starting offset of the first subsequent epoch.
+ epochAndOffset = new AbstractMap.SimpleImmutableEntry<>(floorEntry.getValue().epoch, higherEntry.getValue().startOffset);
+ }
+ }
+ }
+ log.trace("Processed end offset request for epoch {} and returning epoch {} " + "with end offset {} from epoch cache of size {}}", requestedEpoch, epochAndOffset.getKey(), epochAndOffset.getValue(), epochs.size());
Review Comment:
No need for the string concat here. Also, since this is a trace log, we may want to have it under a if check (to avoid the array allocation for the parameters, etc.).
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