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本文主要研究一下rocketmq的consumeConcurrentlyMaxSpan

consumeConcurrentlyMaxSpan

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/consumer/DefaultMQPushConsumer.java

public class DefaultMQPushConsumer extends ClientConfig implements MQPushConsumer {

    private final InternalLogger log = ClientLogger.getLog();

    //......

    /**
     * Concurrently max span offset.it has no effect on sequential consumption
     */
    private int consumeConcurrentlyMaxSpan = 2000;

    public int getConsumeConcurrentlyMaxSpan() {
        return consumeConcurrentlyMaxSpan;
    }

    public void setConsumeConcurrentlyMaxSpan(int consumeConcurrentlyMaxSpan) {
        this.consumeConcurrentlyMaxSpan = consumeConcurrentlyMaxSpan;
    }

    //......
}

• DefaultMQPushConsumer定义了consumeConcurrentlyMaxSpan属性，默认值为2000

checkConfig

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/impl/consumer/DefaultMQPushConsumerImpl.java

public class DefaultMQPushConsumerImpl implements MQConsumerInner {
    //......

    private void checkConfig() throws MQClientException {
        Validators.checkGroup(this.defaultMQPushConsumer.getConsumerGroup());

        //......

        // consumeConcurrentlyMaxSpan
        if (this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan() < 1
            || this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan() > 65535) {
            throw new MQClientException(
                "consumeConcurrentlyMaxSpan Out of range [1, 65535]"
                    + FAQUrl.suggestTodo(FAQUrl.CLIENT_PARAMETER_CHECK_URL),
                null);
        }

        //......
    }

    //......
}

• checkConfig方法要求defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()大于等于1且小于等于65535

pullMessage

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/impl/consumer/DefaultMQPushConsumerImpl.java

public class DefaultMQPushConsumerImpl implements MQConsumerInner {

    /**
     * Delay some time when exception occur
     */
    private static final long PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION = 3000;
    /**
     * Flow control interval
     */
    private static final long PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL = 50;

    //......

    public void pullMessage(final PullRequest pullRequest) {
        final ProcessQueue processQueue = pullRequest.getProcessQueue();
        if (processQueue.isDropped()) {
            log.info("the pull request[{}] is dropped.", pullRequest.toString());
            return;
        }

        pullRequest.getProcessQueue().setLastPullTimestamp(System.currentTimeMillis());

        //......

        if (!this.consumeOrderly) {
            if (processQueue.getMaxSpan() > this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()) {
                this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
                if ((queueMaxSpanFlowControlTimes++ % 1000) == 0) {
                    log.warn(
                        "the queue's messages, span too long, so do flow control, minOffset={}, maxOffset={}, maxSpan={}, pullRequest={}, flowControlTimes={}",
                        processQueue.getMsgTreeMap().firstKey(), processQueue.getMsgTreeMap().lastKey(), processQueue.getMaxSpan(),
                        pullRequest, queueMaxSpanFlowControlTimes);
                }
                return;
            }
        } else {
            if (processQueue.isLocked()) {
                if (!pullRequest.isLockedFirst()) {
                    final long offset = this.rebalanceImpl.computePullFromWhere(pullRequest.getMessageQueue());
                    boolean brokerBusy = offset < pullRequest.getNextOffset();
                    log.info("the first time to pull message, so fix offset from broker. pullRequest: {} NewOffset: {} brokerBusy: {}",
                        pullRequest, offset, brokerBusy);
                    if (brokerBusy) {
                        log.info("[NOTIFYME]the first time to pull message, but pull request offset larger than broker consume offset. pullRequest: {} NewOffset: {}",
                            pullRequest, offset);
                    }

                    pullRequest.setLockedFirst(true);
                    pullRequest.setNextOffset(offset);
                }
            } else {
                this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
                log.info("pull message later because not locked in broker, {}", pullRequest);
                return;
            }
        }

        //......        

    }

    private void executePullRequestLater(final PullRequest pullRequest, final long timeDelay) {
        this.mQClientFactory.getPullMessageService().executePullRequestLater(pullRequest, timeDelay);
    }

    //......
}   

• pullMessage方法在不是consumeOrderly的时候，会判断processQueue.getMaxSpan()是否大于this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()，大于则执行executePullRequestLater方法进行流控，PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL默认值为50

ProcessQueue

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/impl/consumer/ProcessQueue.java

public class ProcessQueue {
    public final static long REBALANCE_LOCK_MAX_LIVE_TIME =
        Long.parseLong(System.getProperty("rocketmq.client.rebalance.lockMaxLiveTime", "30000"));
    public final static long REBALANCE_LOCK_INTERVAL = Long.parseLong(System.getProperty("rocketmq.client.rebalance.lockInterval", "20000"));
    private final static long PULL_MAX_IDLE_TIME = Long.parseLong(System.getProperty("rocketmq.client.pull.pullMaxIdleTime", "120000"));
    private final InternalLogger log = ClientLogger.getLog();
    private final ReadWriteLock lockTreeMap = new ReentrantReadWriteLock();
    private final TreeMap<Long, MessageExt> msgTreeMap = new TreeMap<Long, MessageExt>();

    //......

    public long getMaxSpan() {
        try {
            this.lockTreeMap.readLock().lockInterruptibly();
            try {
                if (!this.msgTreeMap.isEmpty()) {
                    return this.msgTreeMap.lastKey() - this.msgTreeMap.firstKey();
                }
            } finally {
                this.lockTreeMap.readLock().unlock();
            }
        } catch (InterruptedException e) {
            log.error("getMaxSpan exception", e);
        }

        return 0;
    }

    //......
}

• ProcessQueue的getMaxSpan取的是msgTreeMap.lastKey() - this.msgTreeMap.firstKey()

PullMessageService

rocketmq-client-4.5.2-sources.jar!/org/apache/rocketmq/client/impl/consumer/PullMessageService.java

public class PullMessageService extends ServiceThread {
    private final InternalLogger log = ClientLogger.getLog();
    private final LinkedBlockingQueue<PullRequest> pullRequestQueue = new LinkedBlockingQueue<PullRequest>();
    private final MQClientInstance mQClientFactory;
    private final ScheduledExecutorService scheduledExecutorService = Executors
        .newSingleThreadScheduledExecutor(new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                return new Thread(r, "PullMessageServiceScheduledThread");
            }
        });

    public PullMessageService(MQClientInstance mQClientFactory) {
        this.mQClientFactory = mQClientFactory;
    }

    public void executePullRequestLater(final PullRequest pullRequest, final long timeDelay) {
        if (!isStopped()) {
            this.scheduledExecutorService.schedule(new Runnable() {
                @Override
                public void run() {
                    PullMessageService.this.executePullRequestImmediately(pullRequest);
                }
            }, timeDelay, TimeUnit.MILLISECONDS);
        } else {
            log.warn("PullMessageServiceScheduledThread has shutdown");
        }
    }

    public void executePullRequestImmediately(final PullRequest pullRequest) {
        try {
            this.pullRequestQueue.put(pullRequest);
        } catch (InterruptedException e) {
            log.error("executePullRequestImmediately pullRequestQueue.put", e);
        }
    }

    @Override
    public void run() {
        log.info(this.getServiceName() + " service started");

        while (!this.isStopped()) {
            try {
                PullRequest pullRequest = this.pullRequestQueue.take();
                this.pullMessage(pullRequest);
            } catch (InterruptedException ignored) {
            } catch (Exception e) {
                log.error("Pull Message Service Run Method exception", e);
            }
        }

        log.info(this.getServiceName() + " service end");
    }

    private void pullMessage(final PullRequest pullRequest) {
        final MQConsumerInner consumer = this.mQClientFactory.selectConsumer(pullRequest.getConsumerGroup());
        if (consumer != null) {
            DefaultMQPushConsumerImpl impl = (DefaultMQPushConsumerImpl) consumer;
            impl.pullMessage(pullRequest);
        } else {
            log.warn("No matched consumer for the PullRequest {}, drop it", pullRequest);
        }
    }

    //......
}

• executePullRequestLater方法往scheduledExecutorService调度一个延时任务，该任务执行的是executePullRequestImmediately(pullRequest)方法，该方法往pullRequestQueue队列放入pullRequest；run方法会从pullRequestQueue取pullRequest，然后执行pullMessage方法；pullMessage方法首先通过mQClientFactory.selectConsumer取出consumer，然后执行该consumer的pullMessage方法

小结

DefaultMQPushConsumer定义了consumeConcurrentlyMaxSpan属性，默认值为2000；DefaultMQPushConsumerImpl的pullMessage方法在不是consumeOrderly的时候，会判断processQueue.getMaxSpan()是否大于this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()，大于则执行executePullRequestLater方法进行流控，PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL默认值为50

doc

• DefaultMQPushConsumer