Rocketmq 定时消息源码分析
定时消息定义
生产者将消息投放到broker后，不会马上被消费者消费。需要等待到特定时间才会被消费。
调用链路
- producer 将定时消息写入commitLog
- 线程ReputThead 休息1毫秒，读取一次commitlog数据，写入ConsumeQueue和IndexFile
- 线程ScheduledService 首次延时1秒执行，以后延迟100毫秒执行。职责是将到期的延时消息投放普通消息
定时消息详细介绍
核心类
ScheduedMessageService
rocketmq 不支持任意精度的定时消息，仅支持指定级别的定时消息。
核心配置
delayLevelTable
1s 5s 10s 30s 1m 2m ..... 1h 2h 每个级别对应一个TimerTask
offsetTable
消息消费进度维护
具体逻辑
定时消息写入commitlog
检查msg的DelayTimeLevel ，若大于0.重写消息主题改成SCHEDUELED_TOPIC_XXXX
按延迟级别改写队列id。
CommitLog#putMessage
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());
}
topic = TopicValidator.RMQ_SYS_SCHEDULE_TOPIC;
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);
}ScheduledMessageService#delayLevel2QueueId
public static int delayLevel2QueueId(final int delayLevel) {
return delayLevel - 1;
}时序图
定时消息写入ConsumeQueue
DefaultMessageStore.ReputMessageService#run
休息1毫秒执行一次
@Override
public void run() {
DefaultMessageStore.log.info(this.getServiceName() + " service started");
while (!this.isStopped()) {
try {
Thread.sleep(1);
this.doReput();
} catch (Exception e) {
DefaultMessageStore.log.warn(this.getServiceName() + " service has exception. ", e);
}
}
DefaultMessageStore.log.info(this.getServiceName() + " service end");
}DefaultMessageStore.ReputMessageService#run
从commitLog取出数据，
SelectMappedBufferResult result = DefaultMessageStore.this.commitLog.getData(reputFromOffset);
if (result != null) {
try {
this.reputFromOffset = result.getStartOffset();
for (int readSize = 0; readSize < result.getSize() && doNext; ) {
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) {
DefaultMessageStore.this.doDispatch(dispatchRequest);若消息主题是 SCHEDULED_TOPIC_XXXX ，则设置consumeQueue的tagsCode是延时消息的到期时间
CommitLog#checkMessageAndReturnSize
String t = propertiesMap.get(MessageConst.PROPERTY_DELAY_TIME_LEVEL);
if (TopicValidator.RMQ_SYS_SCHEDULE_TOPIC.equals(topic) && t != null) {
int delayLevel = Integer.parseInt(t);
if (delayLevel > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
delayLevel = this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel();
}
if (delayLevel > 0) {
tagsCode = this.defaultMessageStore.getScheduleMessageService().computeDeliverTimestamp(delayLevel,
storeTimestamp);
}
}返回对象DispatchRquest
int readLength = calMsgLength(sysFlag, bodyLen, topicLen, propertiesLength);
if (totalSize != readLength) {
doNothingForDeadCode(reconsumeTimes);
doNothingForDeadCode(flag);
doNothingForDeadCode(bornTimeStamp);
doNothingForDeadCode(byteBuffer1);
doNothingForDeadCode(byteBuffer2);
log.error(
"[BUG]read total count not equals msg total size. totalSize={}, readTotalCount={}, bodyLen={}, topicLen={}, propertiesLength={}",
totalSize, readLength, bodyLen, topicLen, propertiesLength);
return new DispatchRequest(totalSize, false/* success */);
}
return new DispatchRequest(
topic,
queueId,
physicOffset,
totalSize,
tagsCode,
storeTimestamp,
queueOffset,
keys,
uniqKey,
sysFlag,
preparedTransactionOffset,
propertiesMap
);
} catch (Exception e) {
}
return new DispatchRequest(-1, false /* success */);
}追加到ConsumeQueue和IndexFile
DefaultMessageStore.this.doDispatch(dispatchRequest);
public void doDispatch(DispatchRequest req) {
for (CommitLogDispatcher dispatcher : this.dispatcherList) {
dispatcher.dispatch(req);
}
}
时序图
检查定时消息线程配置
首次执行延迟1秒
this.timer = new Timer("ScheduleMessageTimerThread", true);
for (Map.Entry entry : this.delayLevelTable.entrySet()) {
Integer level = entry.getKey();
Long timeDelay = entry.getValue();
Long offset = this.offsetTable.get(level);
if (null == offset) {
offset = 0L;
}
if (timeDelay != null) {
this.timer.schedule(new DeliverDelayedMessageTimerTask(level, offset), FIRST_DELAY_TIME);
}
} 以后延迟100毫秒执行
ScheduleMessageService.this.timer.schedule(new DeliverDelayedMessageTimerTask(this.delayLevel,
failScheduleOffset), DELAY_FOR_A_WHILE);线程检查ConsumeQueue
取出指定主题和队列的数据。
public static final String RMQ_SYS_SCHEDULE_TOPIC = "SCHEDULE_TOPIC_XXXX";
ConsumeQueue cq =
ScheduleMessageService.this.defaultMessageStore.findConsumeQueue(TopicValidator.RMQ_SYS_SCHEDULE_TOPIC,
delayLevel2QueueId(delayLevel));
long failScheduleOffset = offset;
if (cq != null) {
SelectMappedBufferResult bufferCQ = cq.getIndexBuffer(this.offset);检查延迟消息是否到期
correctDeliverTimestamp 检查是否到期
ConsumeQueueExt.CqExtUnit cqExtUnit = new ConsumeQueueExt.CqExtUnit();
for (; i < bufferCQ.getSize(); i += ConsumeQueue.CQ_STORE_UNIT_SIZE) {
long offsetPy = bufferCQ.getByteBuffer().getLong();
int sizePy = bufferCQ.getByteBuffer().getInt();
long tagsCode = bufferCQ.getByteBuffer().getLong();
if (cq.isExtAddr(tagsCode)) {
if (cq.getExt(tagsCode, cqExtUnit)) {
tagsCode = cqExtUnit.getTagsCode();
} else {
//can't find ext content.So re compute tags code.
log.error("[BUG] can't find consume queue extend file content!addr={}, offsetPy={}, sizePy={}",
tagsCode, offsetPy, sizePy);
long msgStoreTime = defaultMessageStore.getCommitLog().pickupStoreTimestamp(offsetPy, sizePy);
tagsCode = computeDeliverTimestamp(delayLevel, msgStoreTime);
}
}
long now = System.currentTimeMillis();
long deliverTimestamp = this.correctDeliverTimestamp(now, tagsCode);
private long correctDeliverTimestamp(final long now, final long deliverTimestamp) {
long result = deliverTimestamp;
long maxTimestamp = now + ScheduleMessageService.this.delayLevelTable.get(this.delayLevel);
if (deliverTimestamp > maxTimestamp) {
result = now;
}
return result;
}投放普通消息到CommitLog
创建普通消息
private MessageExtBrokerInner messageTimeup(MessageExt msgExt) {
MessageExtBrokerInner msgInner = new MessageExtBrokerInner();
msgInner.setBody(msgExt.getBody());
msgInner.setFlag(msgExt.getFlag());
MessageAccessor.setProperties(msgInner, msgExt.getProperties());
TopicFilterType topicFilterType = MessageExt.parseTopicFilterType(msgInner.getSysFlag());
long tagsCodeValue =
MessageExtBrokerInner.tagsString2tagsCode(topicFilterType, msgInner.getTags());
msgInner.setTagsCode(tagsCodeValue);
msgInner.setPropertiesString(MessageDecoder.messageProperties2String(msgExt.getProperties()));
msgInner.setSysFlag(msgExt.getSysFlag());
msgInner.setBornTimestamp(msgExt.getBornTimestamp());
msgInner.setBornHost(msgExt.getBornHost());
msgInner.setStoreHost(msgExt.getStoreHost());
msgInner.setReconsumeTimes(msgExt.getReconsumeTimes());
msgInner.setWaitStoreMsgOK(false);
MessageAccessor.clearProperty(msgInner, MessageConst.PROPERTY_DELAY_TIME_LEVEL);
//原消息主题
msgInner.setTopic(msgInner.getProperty(MessageConst.PROPERTY_REAL_TOPIC));
//原消息队列id
String queueIdStr = msgInner.getProperty(MessageConst.PROPERTY_REAL_QUEUE_ID);
int queueId = Integer.parseInt(queueIdStr);
msgInner.setQueueId(queueId);
return msgInner;
}写入消息
PutMessageResult putMessageResult =
ScheduleMessageService.this.writeMessageStore
.putMessage(msgInner);