divijvaidya commented on code in PR #13456: URL: https://github.com/apache/kafka/pull/13456#discussion_r1154306477
########## storage/src/main/java/org/apache/kafka/storage/internals/checkpoint/InMemoryLeaderEpochCheckpoint.java: ########## @@ -0,0 +1,58 @@ +/* + * 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 + */ +public class InMemoryLeaderEpochCheckpoint implements LeaderEpochCheckpoint { Review Comment: Thanks for the explanation @showuon. It's clear now. To rephrase what you mentioned (correct me if I misunderstood) we want to create an in-memory copy of the `LeaderEpochCheckpointCache` so that we can modify it without modifying the original checkpointcache & checkpoint. Is that right? At the end of the day, RLSM requires `Map<Int, Long> segmentLeaderEpochs()` and the source is `LeaderEpochCheckpointCache`. I was wondering if it would be possible to copy the `LeaderEpochCheckpointCache` into an intermediate data structure (which doesn't have to be of type LeaderEpochCheckpointCache, hence decoupling it from the need to create a dummy `InMemoryLeaderEpochCheckpoint `) and then using that intermediate data structure to extract the required Map (after whatever manipulation we want to do with it). Similar logic could be employed for the requirement to provide `ByteBuffer leaderEpochIndex` to `LogSegmentData`. Thoughts? Having said that I don't want to block this PR on this refactoring discussion. It can be done separately after this is merged. In the scope of this PR, if you add a comment to InMemoryLeaderEpochCheckpoint which could explain future reader of the code about the purpose of this class (the way you described in the comment above), that would be enough to make me happy. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
