RocketMQ消息存储的示例分析

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先梳理消息存储主干流程。本分切分为两部分，第一部分消息存储流程概览，主要为校验流程；第二部分CommitLog存储概览，即消息存储流程。

1.消息存储流程概览

调用链

@1 SendMessageProcessor#sendMessage
//消息存储
PutMessageResult putMessageResult = this.brokerController.getMessageStore().putMessage(msgInner);
@2 DefaultMessageStore#putMessage

流程图

备注：PageCache是否繁忙，内存锁定时间为1秒，在集群流量负载很高时可能出现system busy，broker buys等异常信息。

源代码

public PutMessageResult putMessage(MessageExtBrokerInner msg) {
//如果消息存储服务已关闭，则消息写入被拒绝
if (this.shutdown) {
log.warn("message store has shutdown, so putMessage is forbidden");
return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
}
//Slave不处理消息存储
if (BrokerRole.SLAVE == this.messageStoreConfig.getBrokerRole()) {
long value = this.printTimes.getAndIncrement();
if ((value % 50000) == 0) {
log.warn("message store is slave mode, so putMessage is forbidden ");
}
return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
}
//如果消息存储服务不可写，则消息写入会被拒绝
//出现该错误可能磁盘已满
if (!this.runningFlags.isWriteable()) {
long value = this.printTimes.getAndIncrement();
if ((value % 50000) == 0) {
log.warn("message store is not writeable, so putMessage is forbidden " + this.runningFlags.getFlagBits());
}
return new PutMessageResult(PutMessageStatus.SERVICE_NOT_AVAILABLE, null);
} else {
this.printTimes.set(0);
}
//Topic长度的限制不能超过127个字节
if (msg.getTopic().length() > Byte.MAX_VALUE) {
log.warn("putMessage message topic length too long " + msg.getTopic().length());
return new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, null);
}
//消息属性长度检查不能超过32K
if (msg.getPropertiesString() != null && msg.getPropertiesString().length() > Short.MAX_VALUE) {
log.warn("putMessage message properties length too long " + msg.getPropertiesString().length());
return new PutMessageResult(PutMessageStatus.PROPERTIES_SIZE_EXCEEDED, null);
}
//判断PageCache是否繁忙：阀值[osPageCacheBusyTimeOutMills = 1000 ] 比较时间为当前时间与Commit Lock时间之差
//如果返回true，意味着此时有消息在写入CommitLog，且那条消息的写入耗时较长（超过1s），则本条消息不再写入
//返回内存页写入繁忙
if (this.isOSPageCacheBusy()) {
return new PutMessageResult(PutMessageStatus.OS_PAGECACHE_BUSY, null);
}
long beginTime = this.getSystemClock().now();
//将消息写入CommitLog
PutMessageResult result = this.commitLog.putMessage(msg);
//消息写入时间过长，发出警告
long eclipseTime = this.getSystemClock().now() - beginTime;
if (eclipseTime > 500) {
log.warn("putMessage not in lock eclipse time(ms)={}, bodyLength={}", eclipseTime, msg.getBody().length);
}
//对消息的存储耗时进行分级记录，并记录当前所有消息存储时的最大耗时
this.storeStatsService.setPutMessageEntireTimeMax(eclipseTime);
//记录存粗失败次数
if (null == result || !result.isOk()) {
this.storeStatsService.getPutMessageFailedTimes().incrementAndGet();
}
return result;
}

2.CommitLog存储流程

调用链

@1 DefaultMessageStore#putMessage
//将消息写入CommitLog
PutMessageResult result = this.commitLog.putMessage(msg);
@2 CommitLog#putMessage

流程图

备注：此时写入消息并没有写入磁盘，而是写入了writeBuffer或者mappedByteBuffer（PageCache或堆外内存）

源代码

public PutMessageResult putMessage(final MessageExtBrokerInner msg) {
// Set the storage time
//设置消息存储时间（存储到Broker的时间）
msg.setStoreTimestamp(System.currentTimeMillis());
// Set the message body BODY CRC (consider the most appropriate setting
// on the client)
//Message Body的循环冗余校验码，防止消息体内容被篡改
msg.setBodyCRC(UtilAll.crc32(msg.getBody()));
// Back to Results
AppendMessageResult result = null;
//统计存储耗时相关的Metric
StoreStatsService storeStatsService = this.defaultMessageStore.getStoreStatsService();
String topic = msg.getTopic();
int queueId = msg.getQueueId();
//获取消息类型
final int tranType = MessageSysFlag.getTransactionValue(msg.getSysFlag());
//不处理事务消息
//重试(延时)消息发到SCHEDULE_TOPIC中
if (tranType == MessageSysFlag.TRANSACTION_NOT_TYPE//
|| tranType == MessageSysFlag.TRANSACTION_COMMIT_TYPE) {
// Delay Delivery
//延时投递时间级别
if (msg.getDelayTimeLevel() > 0) {
if (msg.getDelayTimeLevel() > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
msg.setDelayTimeLevel(this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel());
}
//将Topic更改为 SCHEDULE_TOPIC_XXXX
topic = ScheduleMessageService.SCHEDULE_TOPIC;
//根据延时级别获取延时消息新队列ID（queueId等于延时级别-1）
queueId = ScheduleMessageService.delayLevel2QueueId(msg.getDelayTimeLevel());
// Backup real topic, queueId
//将消息中原topic和queueId存入到消息属性中
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);
}
}
long eclipseTimeInLock = 0;
MappedFile unlockMappedFile = null;
//获取最新的日志文件CommitLog 内存映射文件 零拷贝
//mappedFileQueue 管理这些连续的CommitLog文件
//MappedFile 和 MappedFileQueue高性能的磁盘接口
//mappedFileQueue可以理解为commitLog文件夹，而MappedFile对应文件夹下的文件
MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();
//加锁，默认使用自旋锁。//依赖于messageStoreConfig#useReentrantLockWhenPutMessage配置
//putMessage会有多个工作线程并行处理，所以需要加锁。串行写入commitLog
putMessageLock.lock(); //spin or ReentrantLock ,depending on store config
try {
long beginLockTimestamp = this.defaultMessageStore.getSystemClock().now();
this.beginTimeInLock = beginLockTimestamp;
// Here settings are stored timestamp, in order to ensure an orderly
// global
//再次设置时间戳全局有序
msg.setStoreTimestamp(beginLockTimestamp);
//文件已满或者没有映射文件重新创建一个文件
if (null == mappedFile || mappedFile.isFull()) {
mappedFile = this.mappedFileQueue.getLastMappedFile(0); // Mark: NewFile may be cause noise
}
//创建映射文件失败（可能磁盘已满）
if (null == mappedFile) {
log.error("create maped file1 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
//消息写入完成后，先将beginTimeInLock设置为0，然后释放锁
//该值用来计算消息写入耗时。写入新消息前，会根据该值来检查操作系统内存页写入是否繁忙
//如果上一条消息在1s内没有成功写入，则本次消息不再写入
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, null);
}
//向映射文件中写入消息
//注意：只是将消息写入映射文件中的writeBuffer/mappedByteBuffer，没有刷盘
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
switch (result.getStatus()) {
case PUT_OK: //消息成功写入
break;
//文件已经到结尾了，重新建一个新的mappedFile.
case END_OF_FILE: //当前CommitLog可用空间不足
unlockMappedFile = mappedFile;
// Create a new file, re-write the message
//创建新的CommitLog，并重新写入消息
mappedFile = this.mappedFileQueue.getLastMappedFile(0);
if (null == mappedFile) {
// XXX: warn and notify me
log.error("create maped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result);
}
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
break;
case MESSAGE_SIZE_EXCEEDED: //消息长度超过了最大阀值
case PROPERTIES_SIZE_EXCEEDED: //消息属性超过了最大阀值
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, result);
case UNKNOWN_ERROR: //未知错误
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
default:
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
}
eclipseTimeInLock = this.defaultMessageStore.getSystemClock().now() - beginLockTimestamp;
beginTimeInLock = 0;
} finally {
putMessageLock.unlock(); //释放锁
}
if (eclipseTimeInLock > 500) {
log.warn("[NOTIFYME]putMessage in lock cost time(ms)={}, bodyLength={} AppendMessageResult={}", eclipseTimeInLock, msg.getBody().length, result);
}
if (null != unlockMappedFile && this.defaultMessageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
this.defaultMessageStore.unlockMappedFile(unlockMappedFile);
}
PutMessageResult putMessageResult = new PutMessageResult(PutMessageStatus.PUT_OK, result);
// Statistics Metrics指标
storeStatsService.getSinglePutMessageTopicTimesTotal(msg.getTopic()).incrementAndGet();
storeStatsService.getSinglePutMessageTopicSizeTotal(topic).addAndGet(result.getWroteBytes());
//同步刷盘或者异步刷盘
handleDiskFlush(result, putMessageResult, msg);
//主从同步
handleHA(result, putMessageResult, msg);
return putMessageResult;
}

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