RocketMQ中broker消息存储之如何实现消息转储
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broker在接收到producer发送的消息之后，首先会将消息存储到CommitLog的末尾，然后通过一个异步的分发线程ReputMessageService将消息转储到ConsumeQueue以及IndexFile中。
转储的核心逻辑在ReputMessageService.doReput中：
// DefaultMessageStore.ReputMessageService
private void doReput() {
if (this.reputFromOffset < DefaultMessageStore.this.commitLog.getMinOffset()) {
log.warn("The reputFromOffset={} is smaller than minPyOffset={}, this usually indicate that the dispatch behind too much and the commitlog has expired.",
this.reputFromOffset, DefaultMessageStore.this.commitLog.getMinOffset());
this.reputFromOffset = DefaultMessageStore.this.commitLog.getMinOffset();
}
for (boolean doNext = true; this.isCommitLogAvailable() && doNext; ) {
if (DefaultMessageStore.this.getMessageStoreConfig().isDuplicationEnable()
&& this.reputFromOffset >= DefaultMessageStore.this.getConfirmOffset()) {
break;
}
// 1. 获取reputFromOffset偏移所指向的数据
SelectMappedBufferResult result = DefaultMessageStore.this.commitLog.getData(reputFromOffset);
if (result != null) {
try {
this.reputFromOffset = result.getStartOffset();
for (int readSize = 0; readSize < result.getSize() && doNext; ) {
// 2. 解析消息体
DispatchRequest dispatchRequest =
DefaultMessageStore.this.commitLog.checkMessageAndReturnSize(result.getByteBuffer(), false, false);
int size = dispatchRequest.getBufferSize() == -1 ? dispatchRequest.getMsgSize() : dispatchRequest.getBufferSize();
if (dispatchRequest.isSuccess()) {
if (size > 0) {
// 3. 执行分发
DefaultMessageStore.this.doDispatch(dispatchRequest);
// ...
this.reputFromOffset += size;
readSize += size;
// ...
} else if (size == 0) {
this.reputFromOffset = DefaultMessageStore.this.commitLog.rollNextFile(this.reputFromOffset);
readSize = result.getSize();
}
} else if (!dispatchRequest.isSuccess()) {
// ...
}
}
} finally {
result.release();
}
} else {
doNext = false;
}
}
}ConsumeQueue的插入操作如下：
// ConsumeQueue.java
private boolean putMessagePositionInfo(final long offset, final int size, final long tagsCode,
final long cqOffset) {
if (offset + size <= this.maxPhysicOffset) {
log.warn("Maybe try to build consume queue repeatedly maxPhysicOffset={} phyOffset={}", maxPhysicOffset, offset);
return true;
}
// 1. 将commitlog offset/msg size/tags code写到内存缓存
this.byteBufferIndex.flip();
this.byteBufferIndex.limit(CQ_STORE_UNIT_SIZE);
this.byteBufferIndex.putLong(offset);
this.byteBufferIndex.putInt(size);
this.byteBufferIndex.putLong(tagsCode);
final long expectLogicOffset = cqOffset * CQ_STORE_UNIT_SIZE; // ConsumeQueue中偏移
// 2. 获取最后一个MappedFile
MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile(expectLogicOffset);
if (mappedFile != null) {
// ...
this.maxPhysicOffset = offset + size;
// 3. 写入索引数据
return mappedFile.appendMessage(this.byteBufferIndex.array());
}
return false;
}IndexFile的写入逻辑如下：
// IndexService.java
public void buildIndex(DispatchRequest req) {
IndexFile indexFile = retryGetAndCreateIndexFile();
if (indexFile != null) {
long endPhyOffset = indexFile.getEndPhyOffset();
DispatchRequest msg = req;
String topic = msg.getTopic();
String keys = msg.getKeys();
if (msg.getCommitLogOffset() < endPhyOffset) {
return;
}
// ...
if (keys != null && keys.length() > 0) {
String[] keyset = keys.split(MessageConst.KEY_SEPARATOR);
for (int i = 0; i < keyset.length; i++) { // 为每个key执行写入
String key = keyset[i];
if (key.length() > 0) {
indexFile = putKey(indexFile, msg, buildKey(topic, key));
if (indexFile == null) {
log.error("putKey error commitlog {} uniqkey {}", req.getCommitLogOffset(), req.getUniqKey());
return;
}
}
}
}
} else {
log.error("build index error, stop building index");
}
}
private IndexFile putKey(IndexFile indexFile, DispatchRequest msg, String idxKey) {
for (boolean ok = indexFile.putKey(idxKey, msg.getCommitLogOffset(), msg.getStoreTimestamp()); !ok; ) {
log.warn("Index file [" + indexFile.getFileName() + "] is full, trying to create another one");
indexFile = retryGetAndCreateIndexFile(); // 文件已满，重试
if (null == indexFile) {
return null;
}
ok = indexFile.putKey(idxKey, msg.getCommitLogOffset(), msg.getStoreTimestamp());
}
return indexFile;
}消息转储的整体流程如下图：
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