satishd commented on a change in pull request #10579:
URL: https://github.com/apache/kafka/pull/10579#discussion_r671094510



##########
File path: 
storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/TopicBasedRemoteLogMetadataManager.java
##########
@@ -0,0 +1,484 @@
+/*
+ * 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.clients.admin.AdminClient;
+import org.apache.kafka.clients.admin.NewTopic;
+import org.apache.kafka.clients.admin.TopicDescription;
+import org.apache.kafka.clients.producer.RecordMetadata;
+import org.apache.kafka.common.KafkaException;
+import org.apache.kafka.common.TopicIdPartition;
+import org.apache.kafka.common.config.TopicConfig;
+import org.apache.kafka.common.errors.RetriableException;
+import org.apache.kafka.common.errors.TopicExistsException;
+import org.apache.kafka.common.internals.FatalExitError;
+import org.apache.kafka.common.utils.KafkaThread;
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.server.log.remote.storage.RemoteLogMetadata;
+import org.apache.kafka.server.log.remote.storage.RemoteLogMetadataManager;
+import org.apache.kafka.server.log.remote.storage.RemoteLogSegmentMetadata;
+import 
org.apache.kafka.server.log.remote.storage.RemoteLogSegmentMetadataUpdate;
+import org.apache.kafka.server.log.remote.storage.RemoteLogSegmentState;
+import 
org.apache.kafka.server.log.remote.storage.RemotePartitionDeleteMetadata;
+import org.apache.kafka.server.log.remote.storage.RemoteStorageException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * This is the {@link RemoteLogMetadataManager} implementation with storage as 
an internal topic with name {@link 
TopicBasedRemoteLogMetadataManagerConfig#REMOTE_LOG_METADATA_TOPIC_NAME}.
+ * This is used to publish and fetch {@link RemoteLogMetadata} for the 
registered user topic partitions with
+ * {@link #onPartitionLeadershipChanges(Set, Set)}. Each broker will have an 
instance of this class and it subscribes
+ * to metadata updates for the registered user topic partitions.
+ */
+public class TopicBasedRemoteLogMetadataManager implements 
RemoteLogMetadataManager {
+    private static final Logger log = 
LoggerFactory.getLogger(TopicBasedRemoteLogMetadataManager.class);
+
+    private volatile boolean configured = false;
+
+    // It indicates whether the close process of this instance is started or 
not via #close() method.
+    // Using AtomicBoolean instead of volatile as it may encounter 
http://findbugs.sourceforge.net/bugDescriptions.html#SP_SPIN_ON_FIELD
+    // if the field is read but not updated in a spin loop like in 
#initializeResources() method.
+    private final AtomicBoolean closing = new AtomicBoolean(false);
+    private final AtomicBoolean initialized = new AtomicBoolean(false);
+    private final Time time = Time.SYSTEM;
+
+    private Thread initializationThread;
+    private volatile ProducerManager producerManager;
+    private volatile ConsumerManager consumerManager;
+
+    // This allows to gracefully close this instance using {@link #close()} 
method while there are some pending or new
+    // requests calling different methods which use the resources like 
producer/consumer managers.
+    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+
+    private final RemotePartitionMetadataStore remotePartitionMetadataStore = 
new RemotePartitionMetadataStore();
+    private volatile TopicBasedRemoteLogMetadataManagerConfig rlmmConfig;
+    private volatile RemoteLogMetadataTopicPartitioner rlmmTopicPartitioner;
+    private final Set<TopicIdPartition> pendingAssignPartitions = 
Collections.synchronizedSet(new HashSet<>());

Review comment:
       It is needed because `pendingAssignPartitions` is updated in both 
`onPartitionLeadershipChanges` and `onStopPartitions` methods which can happen 
concurrently as both of them take read lock.




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