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Posted to jira@kafka.apache.org by "satishd (via GitHub)" <gi...@apache.org> on 2023/04/04 06:55:01 UTC
[GitHub] [kafka] satishd commented on a diff in pull request #13456: KAFKA-14850: introduce InMemoryLeaderEpochCheckpoint
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.
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