satishd commented on code in PR #13456: URL: https://github.com/apache/kafka/pull/13456#discussion_r1156800195
########## storage/src/main/java/org/apache/kafka/storage/internals/checkpoint/InMemoryLeaderEpochCheckpoint.java: ########## @@ -0,0 +1,64 @@ +/* + * 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; +import org.apache.kafka.storage.internals.log.EpochEntry; + +import java.io.BufferedWriter; +import java.io.ByteArrayOutputStream; +import java.io.IOException; +import java.io.OutputStreamWriter; +import java.nio.ByteBuffer; +import java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.Collection; +import java.util.List; + +/** + * This class stores a list of EpochEntry(LeaderEpoch + Offsets) to memory + * + * The motivation for this class is to allow remote log manager to create the RemoteLogSegmentMetadata(RLSM) + * with the correct leader epoch info for a specific segment. To do that, we need to rely on the LeaderEpochCheckpointCache + * to truncate from start and end, to get the epoch info. However, we don't really want to truncate the epochs in cache + * (and write to checkpoint file in the end). So, we introduce this InMemoryLeaderEpochCheckpoint to feed into LeaderEpochCheckpointCache, + * and when we truncate the epoch for RLSM, we can do them in memory without affecting the checkpoint file, and without interacting with file system. + */ +public class InMemoryLeaderEpochCheckpoint implements LeaderEpochCheckpoint { + private List<EpochEntry> epochs = new ArrayList<>(); Review Comment: `epochs` can be initialized as an empty List like `Collections.emptyList()`. ########## storage/src/main/java/org/apache/kafka/storage/internals/checkpoint/InMemoryLeaderEpochCheckpoint.java: ########## @@ -0,0 +1,64 @@ +/* + * 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; +import org.apache.kafka.storage.internals.log.EpochEntry; + +import java.io.BufferedWriter; +import java.io.ByteArrayOutputStream; +import java.io.IOException; +import java.io.OutputStreamWriter; +import java.nio.ByteBuffer; +import java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.Collection; +import java.util.List; + +/** + * This class stores a list of EpochEntry(LeaderEpoch + Offsets) to memory + * + * The motivation for this class is to allow remote log manager to create the RemoteLogSegmentMetadata(RLSM) + * with the correct leader epoch info for a specific segment. To do that, we need to rely on the LeaderEpochCheckpointCache + * to truncate from start and end, to get the epoch info. However, we don't really want to truncate the epochs in cache + * (and write to checkpoint file in the end). So, we introduce this InMemoryLeaderEpochCheckpoint to feed into LeaderEpochCheckpointCache, + * and when we truncate the epoch for RLSM, we can do them in memory without affecting the checkpoint file, and without interacting with file system. + */ +public class InMemoryLeaderEpochCheckpoint implements LeaderEpochCheckpoint { + private List<EpochEntry> epochs = new ArrayList<>(); + + public void write(Collection<EpochEntry> epochs) { + this.epochs.addAll(epochs); + } + + public List<EpochEntry> read() { + return epochs; Review Comment: Return an unmodifiable List like below so that the internal list is unmodifiable from out side of this class. ``` Collections.unmodifiableList(epochs) ``` ########## storage/src/main/java/org/apache/kafka/storage/internals/checkpoint/InMemoryLeaderEpochCheckpoint.java: ########## @@ -0,0 +1,64 @@ +/* + * 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; +import org.apache.kafka.storage.internals.log.EpochEntry; + +import java.io.BufferedWriter; +import java.io.ByteArrayOutputStream; +import java.io.IOException; +import java.io.OutputStreamWriter; +import java.nio.ByteBuffer; +import java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.Collection; +import java.util.List; + +/** + * This class stores a list of EpochEntry(LeaderEpoch + Offsets) to memory + * + * The motivation for this class is to allow remote log manager to create the RemoteLogSegmentMetadata(RLSM) + * with the correct leader epoch info for a specific segment. To do that, we need to rely on the LeaderEpochCheckpointCache + * to truncate from start and end, to get the epoch info. However, we don't really want to truncate the epochs in cache + * (and write to checkpoint file in the end). So, we introduce this InMemoryLeaderEpochCheckpoint to feed into LeaderEpochCheckpointCache, + * and when we truncate the epoch for RLSM, we can do them in memory without affecting the checkpoint file, and without interacting with file system. + */ +public class InMemoryLeaderEpochCheckpoint implements LeaderEpochCheckpoint { + private List<EpochEntry> epochs = new ArrayList<>(); + + public void write(Collection<EpochEntry> epochs) { + this.epochs.addAll(epochs); Review Comment: A new ArrayList with the intended collection can be created here and store like below. ``` this.epochs = new ArrayList<EpochEntry>(epochs) ``` ########## storage/src/main/java/org/apache/kafka/storage/internals/epoch/LeaderEpochFileCache.java: ########## @@ -147,6 +152,16 @@ private List<EpochEntry> removeWhileMatching(Iterator<Map.Entry<Integer, EpochEn return removedEpochs; } + public LeaderEpochFileCache cloneWithLeaderEpochCheckpoint(LeaderEpochCheckpoint leaderEpochCheckpoint) { + lock.readLock().lock(); + try { + flushTo(leaderEpochCheckpoint, epochEntries()); Review Comment: `epochs.values()` can be used instead of calling `epochEnrties()` which creates a new ArrayList that is not needed here. -- This is an automated message from the Apache Git Service. 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