[GitHub] [kafka] ccding commented on a change in pull request #11058: KAFKA-12802 Added a file based cache for consumed remote log metadata for each partition to avoid consuming again incase of broker restarts.

[GitBox <gi...@apache.org>]

ccding commented on a change in pull request #11058:
URL: https://github.com/apache/kafka/pull/11058#discussion_r708590530



##########
File path: storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/CommittedOffsetsFile.java
##########
@@ -0,0 +1,80 @@
+/*
+ * 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.remote.metadata.storage;
+
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.server.common.CheckpointFile;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.regex.Pattern;
+
+/**
+ * This class represents a file containing the committed offsets of remote log metadata partitions.
+ */
+public class CommittedOffsetsFile {
+    private static final int CURRENT_VERSION = 0;
+    private static final String SEPARATOR = " ";
+
+    private static final Pattern MINIMUM_ONE_WHITESPACE = Pattern.compile("\\s+");
+    private final CheckpointFile<Map.Entry<Integer, Long>> checkpointFile;
+
+    CommittedOffsetsFile(File offsetsFile) throws IOException {
+        CheckpointFile.EntryFormatter<Map.Entry<Integer, Long>> formatter = new EntryFormatter();
+        checkpointFile = new CheckpointFile<>(offsetsFile, CURRENT_VERSION, formatter);
+    }
+
+    private static class EntryFormatter implements CheckpointFile.EntryFormatter<Map.Entry<Integer, Long>> {
+
+        @Override
+        public String toString(Map.Entry<Integer, Long> entry) {
+            // Each entry is stored in a new line as <partition-num offset>
+            return entry.getKey() + SEPARATOR + entry.getValue();
+        }
+
+        @Override
+        public Optional<Map.Entry<Integer, Long>> fromString(String line) {
+            String[] strings = MINIMUM_ONE_WHITESPACE.split(line);
+            if (strings.length != 2) {
+                return Optional.empty();
+            }
+            int partition = Integer.parseInt(strings[0]);
+            long offset = Long.parseLong(strings[1]);

Review comment:
       do we need to handle NumberFormatException here?

##########
File path: storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/ConsumerTask.java
##########
@@ -85,21 +90,68 @@
     // Map of remote log metadata topic partition to consumed offsets.
     private final Map<Integer, Long> partitionToConsumedOffsets = new ConcurrentHashMap<>();
 
+    private Map<Integer, Long> committedPartitionToConsumedOffsets = Collections.emptyMap();
+
+    private final long committedOffsetSyncIntervalMs;
+    private CommittedOffsetsFile committedOffsetsFile;
+    private long lastSyncedTimeMs;
+
     public ConsumerTask(KafkaConsumer<byte[], byte[]> consumer,
                         RemotePartitionMetadataEventHandler remotePartitionMetadataEventHandler,
-                        RemoteLogMetadataTopicPartitioner topicPartitioner) {
-        Objects.requireNonNull(consumer);
-        Objects.requireNonNull(remotePartitionMetadataEventHandler);
-        Objects.requireNonNull(topicPartitioner);
-
-        this.consumer = consumer;
-        this.remotePartitionMetadataEventHandler = remotePartitionMetadataEventHandler;
-        this.topicPartitioner = topicPartitioner;
+                        RemoteLogMetadataTopicPartitioner topicPartitioner,
+                        Path committedOffsetsPath,
+                        Time time,
+                        long committedOffsetSyncIntervalMs) {
+        this.consumer = Objects.requireNonNull(consumer);
+        this.remotePartitionMetadataEventHandler = Objects.requireNonNull(remotePartitionMetadataEventHandler);
+        this.topicPartitioner = Objects.requireNonNull(topicPartitioner);
+        this.time = Objects.requireNonNull(time);
+        this.committedOffsetSyncIntervalMs = committedOffsetSyncIntervalMs;
+
+        initializeConsumerAssignment(committedOffsetsPath);
+    }
+
+    private void initializeConsumerAssignment(Path committedOffsetsPath) {
+        try {
+            committedOffsetsFile = new CommittedOffsetsFile(committedOffsetsPath.toFile());
+        } catch (IOException e) {
+            throw new KafkaException(e);
+        }
+
+        Map<Integer, Long> committedOffsets = Collections.emptyMap();
+        try {
+            // Load committed offset and assign them in the consumer.
+            committedOffsets = committedOffsetsFile.readEntries();
+        } catch (IOException e) {
+            // Ignore the error and consumer consumes from the earliest offset.
+            log.error("Encountered error while building committed offsets from the file", e);
+        }
+
+        final Set<Map.Entry<Integer, Long>> entries = committedOffsets.entrySet();

Review comment:
       out of curiosity: what is the purpose of converting a map to a set of map entries?

##########
File path: storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/ConsumerManager.java
##########
@@ -49,21 +52,23 @@
 
     public ConsumerManager(TopicBasedRemoteLogMetadataManagerConfig rlmmConfig,
                            RemotePartitionMetadataEventHandler remotePartitionMetadataEventHandler,
-                           RemoteLogMetadataTopicPartitioner rlmmTopicPartitioner,
+                           RemoteLogMetadataTopicPartitioner topicPartitioner,
                            Time time) {
         this.rlmmConfig = rlmmConfig;
         this.time = time;
 
         //Create a task to consume messages and submit the respective events to RemotePartitionMetadataEventHandler.
         KafkaConsumer<byte[], byte[]> consumer = new KafkaConsumer<>(rlmmConfig.consumerProperties());
-        consumerTask = new ConsumerTask(consumer, remotePartitionMetadataEventHandler, rlmmTopicPartitioner);
+        Path committedOffsetsPath = new File(rlmmConfig.logDir(), COMMITTED_OFFSETS_FILE_NAME).toPath();
+        consumerTask = new ConsumerTask(consumer, remotePartitionMetadataEventHandler, topicPartitioner, committedOffsetsPath, time, 60_000L);

Review comment:
       do we plan to make `60_000L` a variable/configurable in the future? like other intervals in KafkaConfig.




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