RocketMQ源码分析之延迟消息

 

设置延迟消息只需要在消息的属性中设置延迟级别就行，范围在1到18，当消息在存储之前会更换原消息的topic以及队列id，替换成延迟队列统一的topic以及18个队列中的其中一个id。

public void setDelayTimeLevel(int level) {
    this.putProperty(MessageConst.PROPERTY_DELAY_TIME_LEVEL, String.valueOf(level));
}

 

在消息存储类加载的时候，定时消息服务ScheduleMessageService也会跟着加载。解析出18个级别对应的延迟时间。

private String messageDelayLevel = "1s 5s 10s 30s 1m 2m 3m 4m 5m 6m 7m 8m 9m 10m 20m 30m 1h 2h";

public boolean parseDelayLevel() {
    HashMap<String, Long> timeUnitTable = new HashMap<String, Long>();
    timeUnitTable.put("s", 1000L);
    timeUnitTable.put("m", 1000L * 60);
    timeUnitTable.put("h", 1000L * 60 * 60);
    timeUnitTable.put("d", 1000L * 60 * 60 * 24);

    String levelString = this.defaultMessageStore.getMessageStoreConfig().getMessageDelayLevel();
    try {
        String[] levelArray = levelString.split(" ");
        for (int i = 0; i < levelArray.length; i++) {
            String value = levelArray[i];
            String ch = value.substring(value.length() - 1);
            Long tu = timeUnitTable.get(ch);

            int level = i + 1;
            if (level > this.maxDelayLevel) {
                this.maxDelayLevel = level;
            }
            long num = Long.parseLong(value.substring(0, value.length() - 1));
            long delayTimeMillis = tu * num;
            this.delayLevelTable.put(level, delayTimeMillis);
        }
    } catch (Exception e) {
        log.error("parseDelayLevel exception", e);
        log.info("levelString String = {}", levelString);
        return false;
    }

    return true;
}

只有主broker才有启动定时任务，查找每个级别下面对应的偏移量的信息，当第一次的时候默认偏移量是0，总共是18个任务在执行，定时持久化任务。

private final ConcurrentMap<Integer /* level */, Long/* delay timeMillis */> delayLevelTable =
    new ConcurrentHashMap<Integer, Long>(32);

private final ConcurrentMap<Integer /* level */, Long/* offset */> offsetTable =
    new ConcurrentHashMap<Integer, Long>(32);

public void start() {

    for (Map.Entry<Integer, Long> 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);
        }
    }

    this.timer.scheduleAtFixedRate(new TimerTask() {

        @Override
        public void run() {
            try {
                ScheduleMessageService.this.persist();
            } catch (Throwable e) {
                log.error("scheduleAtFixedRate flush exception", e);
            }
        }
    }, 10000, this.defaultMessageStore.getMessageStoreConfig().getFlushDelayOffsetInterval());
}

 

查找SCHEDULE_TOPIC = "SCHEDULE_TOPIC_XXXX"下面每个队列id的消息消费队列，根据偏移量取出对应的数据

public void executeOnTimeup() {
    ConsumeQueue cq =
        ScheduleMessageService.this.defaultMessageStore.findConsumeQueue(SCHEDULE_TOPIC,
            delayLevel2QueueId(delayLevel));

    long failScheduleOffset = offset;

    if (cq != null) {
        SelectMappedBufferResult bufferCQ = cq.getIndexBuffer(this.offset);
        if (bufferCQ != null) {
            try {
                long nextOffset = offset;
                int i = 0;
                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);

                    nextOffset = offset + (i / ConsumeQueue.CQ_STORE_UNIT_SIZE);

                    long countdown = deliverTimestamp - now;

                    if (countdown <= 0) {
                        MessageExt msgExt =
                            ScheduleMessageService.this.defaultMessageStore.lookMessageByOffset(
                                offsetPy, sizePy);

                        if (msgExt != null) {
                            try {
                                MessageExtBrokerInner msgInner = this.messageTimeup(msgExt);
                                PutMessageResult putMessageResult =
                                    ScheduleMessageService.this.defaultMessageStore
                                        .putMessage(msgInner);

                                if (putMessageResult != null
                                    && putMessageResult.getPutMessageStatus() == PutMessageStatus.PUT_OK) {
                                    continue;
                                } else {
                                    // XXX: warn and notify me
                                    log.error(
                                        "ScheduleMessageService, a message time up, but reput it failed, topic: {} msgId {}",
                                        msgExt.getTopic(), msgExt.getMsgId());
                                    ScheduleMessageService.this.timer.schedule(
                                        new DeliverDelayedMessageTimerTask(this.delayLevel,
                                            nextOffset), DELAY_FOR_A_PERIOD);
                                    ScheduleMessageService.this.updateOffset(this.delayLevel,
                                        nextOffset);
                                    return;
                                }
                            } catch (Exception e) {
                                /*
                                 * XXX: warn and notify me



                                 */
                                log.error(
                                    "ScheduleMessageService, messageTimeup execute error, drop it. msgExt="
                                        + msgExt + ", nextOffset=" + nextOffset + ",offsetPy="
                                        + offsetPy + ",sizePy=" + sizePy, e);
                            }
                        }
                    } else {
                        ScheduleMessageService.this.timer.schedule(
                            new DeliverDelayedMessageTimerTask(this.delayLevel, nextOffset),
                            countdown);
                        ScheduleMessageService.this.updateOffset(this.delayLevel, nextOffset);
                        return;
                    }
                } // end of for

                nextOffset = offset + (i / ConsumeQueue.CQ_STORE_UNIT_SIZE);
                ScheduleMessageService.this.timer.schedule(new DeliverDelayedMessageTimerTask(
                    this.delayLevel, nextOffset), DELAY_FOR_A_WHILE);
                ScheduleMessageService.this.updateOffset(this.delayLevel, nextOffset);
                return;
            } finally {

                bufferCQ.release();
            }
        } // end of if (bufferCQ != null)
        else {

            long cqMinOffset = cq.getMinOffsetInQueue();
            if (offset < cqMinOffset) {
                failScheduleOffset = cqMinOffset;
                log.error("schedule CQ offset invalid. offset=" + offset + ", cqMinOffset="
                    + cqMinOffset + ", queueId=" + cq.getQueueId());
            }
        }
    } // end of if (cq != null)

    ScheduleMessageService.this.timer.schedule(new DeliverDelayedMessageTimerTask(this.delayLevel,
        failScheduleOffset), DELAY_FOR_A_WHILE);
}

计算对应的延迟时间已经到达，延迟消息的tagsCode保存的都是延迟后的时间

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;
}

 

当时间到达时，查找消息内容，重新组装消息实体，移除延迟级别属性，还原topic和队列id，然后重新存储消息。如果没有存储成功的话就放进定时程序，稍候再次执行，当延迟时间还没到时，设置对应的延迟时间后放入定时程序。更新对应级别执行到的偏移量信息。

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);

    msgInner.setTopic(msgInner.getProperty(MessageConst.PROPERTY_REAL_TOPIC));

    String queueIdStr = msgInner.getProperty(MessageConst.PROPERTY_REAL_QUEUE_ID);
    int queueId = Integer.parseInt(queueIdStr);
    msgInner.setQueueId(queueId);

    return msgInner;
}