【原】RocketMQ Broker消息处理流程剩余源码解析

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文章目录

DefaultMessageStore

接上文，SendMessageProcessor对象接收到消息之后，会把消息变成存储对象DefaultStoreMessage实例：

DefaultMessageStore的默认存储消息的方法asyncPutMessage如下：

@Override
public CompletableFuture<PutMessageResult> asyncPutMessage(MessageExtBrokerInner msg) {
    PutMessageStatus checkStoreStatus = this.checkStoreStatus();
    if (checkStoreStatus != PutMessageStatus.PUT_OK) {
        return CompletableFuture.completedFuture(new PutMessageResult(checkStoreStatus, null));
    }

    PutMessageStatus msgCheckStatus = this.checkMessage(msg);
    if (msgCheckStatus == PutMessageStatus.MESSAGE_ILLEGAL) {
        return CompletableFuture.completedFuture(new PutMessageResult(msgCheckStatus, null));
    }

    long beginTime = this.getSystemClock().now();
    CompletableFuture<PutMessageResult> putResultFuture = this.commitLog.asyncPutMessage(msg);

    putResultFuture.thenAccept((result) -> {
        long elapsedTime = this.getSystemClock().now() - beginTime;
        if (elapsedTime > 500) {
            log.warn("putMessage not in lock elapsed time(ms)={}, bodyLength={}", elapsedTime, msg.getBody().length);
        }
        this.storeStatsService.setPutMessageEntireTimeMax(elapsedTime);

        if (null == result || !result.isOk()) {
            this.storeStatsService.getPutMessageFailedTimes().incrementAndGet();
        }
    });

    return putResultFuture;
}

整个存储流程的代码还是比较清晰的：

1. 先判断消息是否投放成功 及 检查消息的格式
2. 上述检查都没问题时就会把消息存储在CommitLog里

CompletableFuture<PutMessageResult> putResultFuturethis.commitLog.asyncPutMessage(msg);

CommitLog

Broker接收到消息后，最终消息存储在Commitlog对象中，调用的是CommitLog的putMessage方法

 public CompletableFuture<PutMessageResult> asyncPutMessage(final MessageExtBrokerInner msg) {
        // Set the storage time
        msg.setStoreTimestamp(System.currentTimeMillis());
        // Set the message body BODY CRC (consider the most appropriate setting
        // on the client)
        msg.setBodyCRC(UtilAll.crc32(msg.getBody()));
        // Back to Results
        AppendMessageResult result = null;

        StoreStatsService storeStatsService = this.defaultMessageStore.getStoreStatsService();

        String topic = msg.getTopic();
        int queueId = msg.getQueueId();
		
		// 延时消息处理，事务为TRANSACTION_PREPARED_TYPE 和 TRANSACTION_ROLLBACK_TYPE 消息不支持延时投递
        final int tranType = MessageSysFlag.getTransactionValue(msg.getSysFlag());
        if (tranType == MessageSysFlag.TRANSACTION_NOT_TYPE
                || tranType == MessageSysFlag.TRANSACTION_COMMIT_TYPE) {
            // Delay Delivery
            if (msg.getDelayTimeLevel() > 0) {
                if (msg.getDelayTimeLevel() > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
                    msg.setDelayTimeLevel(this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel());
                }
				// 存储消息时，延时消息进入SCHEDULE_TOPIC_XXXX的主题下
                topic = TopicValidator.RMQ_SYS_SCHEDULE_TOPIC;
                // 消息队列编号 = 延迟级别 - 1
                queueId = ScheduleMessageService.delayLevel2QueueId(msg.getDelayTimeLevel());

                // Backup real topic, queueId
                MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_TOPIC, msg.getTopic());
                MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_QUEUE_ID, String.valueOf(msg.getQueueId()));
                msg.setPropertiesString(MessageDecoder.messageProperties2String(msg.getProperties()));

                msg.setTopic(topic);
                msg.setQueueId(queueId);
            }
        }

        InetSocketAddress bornSocketAddress = (InetSocketAddress) msg.getBornHost();
        if (bornSocketAddress.getAddress() instanceof Inet6Address) {
            msg.setBornHostV6Flag();
        }

        InetSocketAddress storeSocketAddress = (InetSocketAddress) msg.getStoreHost();
        if (storeSocketAddress.getAddress() instanceof Inet6Address) {
            msg.setStoreHostAddressV6Flag();
        }

        PutMessageThreadLocal putMessageThreadLocal = this.putMessageThreadLocal.get();
        PutMessageResult encodeResult = putMessageThreadLocal.getEncoder().encode(msg);
        if (encodeResult != null) {
            return CompletableFuture.completedFuture(encodeResult);
        }
        msg.setEncodedBuff(putMessageThreadLocal.getEncoder().encoderBuffer);
        PutMessageContext putMessageContext = new PutMessageContext(generateKey(putMessageThreadLocal.getKeyBuilder(), msg));

        long elapsedTimeInLock = 0;
        MappedFile unlockMappedFile = null;

		// 加锁，同一时刻只能有一个线程put消息
        putMessageLock.lock(); //spin or ReentrantLock ,depending on store config
        try {
            MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();
            long beginLockTimestamp = this.defaultMessageStore.getSystemClock().now();
            this.beginTimeInLock = beginLockTimestamp;

            // Here settings are stored timestamp, in order to ensure an orderly
            // global
            msg.setStoreTimestamp(beginLockTimestamp);
			// 只有不存在映射文件或文件已存满，才进行创建
            if (null == mappedFile || mappedFile.isFull()) {
                mappedFile = this.mappedFileQueue.getLastMappedFile(0); 
            }
            if (null == mappedFile) {
                log.error("create mapped file1 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
                beginTimeInLock = 0;
                return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, null));
            }
			// 追加消息至MappedFile的缓存中，更新写入位置wrotePosition
            result = mappedFile.appendMessage(msg, this.appendMessageCallback, putMessageContext);
            switch (result.getStatus()) {
                case PUT_OK:
                    break;
                // 当文件剩余空间不足时，创建新的MappedFile并写入
                case END_OF_FILE: 
                    unlockMappedFile = mappedFile;
                    // Create a new file, re-write the message
                    mappedFile = this.mappedFileQueue.getLastMappedFile(0);
                    if (null == mappedFile) {
                        // XXX: warn and notify me
                        log.error("create mapped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
                        beginTimeInLock = 0;
                        return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result));
                    }
                    result = mappedFile.appendMessage(msg, this.appendMessageCallback, putMessageContext);
                    break;
                case MESSAGE_SIZE_EXCEEDED:
                case PROPERTIES_SIZE_EXCEEDED:
                    beginTimeInLock = 0;
                    return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, result));
                case UNKNOWN_ERROR:
                    beginTimeInLock = 0;
                    return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result));
                default:
                    beginTimeInLock = 0;
                    return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result));
            }

            elapsedTimeInLock = this.defaultMessageStore.getSystemClock().now() - beginLockTimestamp;
            beginTimeInLock = 0;
        } finally {
        	// 释放锁
            putMessageLock.unlock();
        }

        /** log **/

        if (null != unlockMappedFile && this.defaultMessageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
            this.defaultMessageStore.unlockMappedFile(unlockMappedFile);
        }

        PutMessageResult putMessageResult = new PutMessageResult(PutMessageStatus.PUT_OK, result);

        // Statistics
        storeStatsService.getSinglePutMessageTopicTimesTotal(msg.getTopic()).incrementAndGet();
        storeStatsService.getSinglePutMessageTopicSizeTotal(topic).addAndGet(result.getWroteBytes());

        CompletableFuture<PutMessageStatus> flushResultFuture = submitFlushRequest(result, msg);
        CompletableFuture<PutMessageStatus> replicaResultFuture = submitReplicaRequest(result, msg);

		// 异步刷盘流程
        return flushResultFuture.thenCombine(replicaResultFuture, (flushStatus, replicaStatus) -> {
            if (flushStatus != PutMessageStatus.PUT_OK) {
                putMessageResult.setPutMessageStatus(flushStatus);
            }
            if (replicaStatus != PutMessageStatus.PUT_OK) {
                putMessageResult.setPutMessageStatus(replicaStatus);
                if (replicaStatus == PutMessageStatus.FLUSH_SLAVE_TIMEOUT) {
                    log.error("do sync transfer other node, wait return, but failed, topic: {} tags: {} client address: {}",
                            msg.getTopic(), msg.getTags(), msg.getBornHostNameString());
                }
            }
            return putMessageResult;
        });
    }

消息在CommitLog文件中是顺序存储的

RocketMQ消息存储在CommitLog文件里，最终落盘，对应的类为MappedFile，它是从MappedFileQueue中获取的，如果对象不存在，就会创建：

MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();

// 只有不存在映射文件或文件已存满，才进行创建
if (null == mappedFile || mappedFile.isFull()) {
    mappedFile = this.mappedFileQueue.getLastMappedFile(0); 
}

创建（获取）完成对象之后就会把消息插入到mappedFile里，如果文件放不下了，则会重新创建一个mappedFile来对其进行写入，最后就是使用异步Future的方式把消息持久化到磁盘上。

MappedFileQueue

上面的源码里首先从MappedFileQueue映射队列尾部中获取MappedFile对象：

public MappedFile getLastMappedFile() {
        MappedFile mappedFileLast = null;

        while (!this.mappedFiles.isEmpty()) {
            try {
                mappedFileLast = this.mappedFiles.get(this.mappedFiles.size() - 1);
                break;
            } catch (IndexOutOfBoundsException e) {
                //continue;
            } catch (Exception e) {
                log.error("getLastMappedFile has exception.", e);
                break;
            }
        }

        return mappedFileLast;
    }

当MappedFile对象为空时，表示MappedFile对象不存在，此时就需要重新创建一个MappedFile对象，相应的方法在MappedFileQueue里

public class MappedFileQueue {
    private static final InternalLogger log = InternalLoggerFactory.getLogger(LoggerName.STORE_LOGGER_NAME);
    private static final InternalLogger LOG_ERROR = InternalLoggerFactory.getLogger(LoggerName.STORE_ERROR_LOGGER_NAME);
	
	// 批量删除文件上限
    private static final int DELETE_FILES_BATCH_MAX = 10;
	// 目录
    private final String storePath;
	// 每个映射文件的大小
    private final int mappedFileSize;
	// 映射文件数组
    private final CopyOnWriteArrayList<MappedFile> mappedFiles = new CopyOnWriteArrayList<MappedFile>();
	// 分配MappedFile服务
    private final AllocateMappedFileService allocateMappedFileService;
	// 最后flush到的offset
    private long flushedWhere = 0;
    // 最后commit到的offset
    private long committedWhere = 0;
	// 最后保存的时间戳
	private volatile long storeTimestamp = 0;
	
	/**
	*	获取最后一个可写入的映射文件
	*	当最后一个文件已经满的时候，创建一个新的文件
	*/
	public MappedFile getLastMappedFile(final long startOffset, boolean needCreate) {
        long createOffset = -1;
        MappedFile mappedFileLast = getLastMappedFile();
		
		// 不存在映射文件
        if (mappedFileLast == null) {
        	// 计算从哪个offset开始
            createOffset = startOffset - (startOffset % this.mappedFileSize);
        }
		
		// 最后一个文件已满
        if (mappedFileLast != null && mappedFileLast.isFull()) {
            createOffset = mappedFileLast.getFileFromOffset() + this.mappedFileSize;
        }
		
		// 创建文件
        if (createOffset != -1 && needCreate) {
            String nextFilePath = this.storePath + File.separator + UtilAll.offset2FileName(createOffset);
            String nextNextFilePath = this.storePath + File.separator
                + UtilAll.offset2FileName(createOffset + this.mappedFileSize);
            MappedFile mappedFile = null;

            if (this.allocateMappedFileService != null) {
                mappedFile = this.allocateMappedFileService.putRequestAndReturnMappedFile(nextFilePath,
                    nextNextFilePath, this.mappedFileSize);
            } else {
                try {
                    mappedFile = new MappedFile(nextFilePath, this.mappedFileSize);
                } catch (IOException e) {
                    log.error("create mappedFile exception", e);
                }
            }

            if (mappedFile != null) {
                if (this.mappedFiles.isEmpty()) {
                    mappedFile.setFirstCreateInQueue(true);
                }
                this.mappedFiles.add(mappedFile);
            }

            return mappedFile;
        }

        return mappedFileLast;
    }

    public MappedFile getLastMappedFile(final long startOffset) {
        return getLastMappedFile(startOffset, true);
    }
}

当获取到的“最后一个”MappedFile不存在或文件已满时，则新建一个，并计算新文件的createOffset

MappedFile

在CommitLog的代码中，最终把消息追加到MappedFile文件的缓冲区中，同时更新其写入位置writePosition，但是还没有刷盘：

result = mappedFile.appendMessages(messageExtBatch, this.appendMessageCallback, putMessageContext);

其中调用了MappedFile的appendMessage方法实现添加消息到消息映射文件：

public AppendMessageResult appendMessagesInner(final MessageExt messageExt, final AppendMessageCallback cb,
            PutMessageContext putMessageContext) {
        assert messageExt != null;
        assert cb != null;

        int currentPos = this.wrotePosition.get();

        if (currentPos < this.fileSize) {
        	// 缓冲区
            ByteBuffer byteBuffer = writeBuffer != null ? writeBuffer.slice() : this.mappedByteBuffer.slice();
            byteBuffer.position(currentPos);
            AppendMessageResult result;
            // 判断是否是批量操作
            if (messageExt instanceof MessageExtBrokerInner) {
                result = cb.doAppend(this.getFileFromOffset(), byteBuffer, this.fileSize - currentPos,
                        (MessageExtBrokerInner) messageExt, putMessageContext);
            } else if (messageExt instanceof MessageExtBatch) {
                result = cb.doAppend(this.getFileFromOffset(), byteBuffer, this.fileSize - currentPos,
                        (MessageExtBatch) messageExt, putMessageContext);
            } else {
                return new AppendMessageResult(AppendMessageStatus.UNKNOWN_ERROR);
            }
            // 更新写入位置 + 写入偏移量
            this.wrotePosition.addAndGet(result.getWroteBytes());
            this.storeTimestamp = result.getStoreTimestamp();
            return result;
        }
        log.error("MappedFile.appendMessage return null, wrotePosition: {} fileSize: {}", currentPos, this.fileSize);
        return new AppendMessageResult(AppendMessageStatus.UNKNOWN_ERROR);
    }

通过源码可以看到，实际上是吧消息放入ByteBuffer，同时更新写入位置和偏移量

submitFlushRequest

提交刷盘请求的源码如下：

public CompletableFuture<PutMessageStatus> submitFlushRequest(AppendMessageResult result, MessageExt messageExt) {
        // 异步flush
        if (FlushDiskType.SYNC_FLUSH == this.defaultMessageStore.getMessageStoreConfig().getFlushDiskType()) {
            final GroupCommitService service = (GroupCommitService) this.flushCommitLogService;
            if (messageExt.isWaitStoreMsgOK()) {
                GroupCommitRequest request = new GroupCommitRequest(result.getWroteOffset() + result.getWroteBytes(),
                        this.defaultMessageStore.getMessageStoreConfig().getSyncFlushTimeout());
                service.putRequest(request);
                return request.future();
            } else {
                service.wakeup();
                return CompletableFuture.completedFuture(PutMessageStatus.PUT_OK);
            }
        }
        // 同步flush
        else {
            if (!this.defaultMessageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
                flushCommitLogService.wakeup();	// 异步，使用MappedByteBuffer（默认策略）
            } else  {
                commitLogService.wakeup();	// 异步，使用字节缓冲区 + FileChannel
            }
            return CompletableFuture.completedFuture(PutMessageStatus.PUT_OK);
        }
    }

CommitLog文件刷盘是由FlushCommitLogService服务具体执行，一共有两种刷盘策略：

1. FlushDiskType.SYNC_FLUSH：同步刷盘
2. FlushDiskType.ASYNC_FLUSH：异步刷盘

同步刷盘的情况下，必须要等到数据刷盘成功后才会有返回结果；如果是异步刷盘，只需要把消息放入内存之后即可返回。

上述策略可以在broker.conf配置文件中进行配置