功能：作为CommitLog文件的索引文件。

本文着重分析为consumequeue/topic/queueId目录下的索引文件。

1.ConsumeQueueStore

public class ConsumeQueueStore {protected final ConcurrentMap<String>, ConcurrentMap<Integer>, ConsumeQueueInterface>> consumeQueueTable;public boolean load() {String storePathRootDir = this.messageStoreConfig.getStorePathRootDir();String storePathConsumeQueue = getStorePathConsumeQueue(storePathRootDir);boolean cqLoadResult = loadConsumeQueues(storePathConsumeQueue, CQType.SimpleCQ);String storePathBatchConsumeQueue = getStorePathBatchConsumeQueue(storePathRootDir);boolean bcqLoadResult = loadConsumeQueues(storePathBatchConsumeQueue, CQType.BatchCQ);return cqLoadResult && bcqLoadResult;}//Broker启动后加载本地的consumequeue文件private boolean loadConsumeQueues(String storePath, CQType cqType) {File dirLogic = new File(storePath);File[] fileTopicList = dirLogic.listFiles();if (fileTopicList != null) {for (File fileTopic : fileTopicList) {String topic = fileTopic.getName();File[] fileQueueIdList = fileTopic.listFiles();if (fileQueueIdList != null) {for (File fileQueueId : fileQueueIdList) {int queueId = Integer.parseInt(fileQueueId.getName());;queueTypeShouldBe(topic, cqType);//选择 ConsumeQueue or BatchConsumeQueue 本文以 ConsumeQueue 作为分析案例ConsumeQueueInterface logic = createConsumeQueueByType(cqType, topic, queueId, storePath);this.putConsumeQueue(topic, queueId, logic);if (!this.load(logic)) {return false;}}}}}return true;}private void putConsumeQueue(final String topic, final int queueId, final ConsumeQueueInterface consumeQueue) {ConcurrentMap<Integer/* queueId */, ConsumeQueueInterface> map = this.consumeQueueTable.get(topic);if (null == map) {map = new ConcurrentHashMap<>();map.put(queueId, consumeQueue);this.consumeQueueTable.put(topic, map);} else {map.put(queueId, consumeQueue);}}public boolean load(ConsumeQueueInterface consumeQueue) {// 通过 topic & queueId 从consumeQueueTable 获取到 对应的FileQueueLifeCycle 即ConsumeQueueFileQueueLifeCycle fileQueueLifeCycle = getLifeCycle(consumeQueue.getTopic(), consumeQueue.getQueueId());return fileQueueLifeCycle.load();}
}

1.1.ConsumeQueue

public class ConsumeQueue implements ConsumeQueueInterface, FileQueueLifeCycle {private final MappedFileQueue mappedFileQueue;@Overridepublic boolean load() {boolean result = this.mappedFileQueue.load();return result;}
}

1.2.MappedFileQueue

mappedFileQueue.load核心功能就是加载consumequeue/topic/queueId目录下的消费索引本地文件。区别CommitLog加载的是/commitlog目录下真正的用户数据。
ConsumeQueue & CommitLog 均持有属性类MappedFileQueue【mmap零拷贝之内存映射的磁盘文件】。

DefaultMessageStore#ReputMessageService

CommitLog & ConsumerQueue 目录下的所有问题在Broker端启动的时候默认都会加载到内存中建立与磁盘之间的映射关系。但是在CommitLog不断增加数据过程中，ConsumerQueue是如何确认每条消息的索引文件呢？