RocketMQ源码分析之消息消费概述

最新推荐文章于 2023-06-10 14:24:01 发布

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最新推荐文章于 2023-06-10 14:24:01 发布

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文章标签： java 分布式大数据

本文链接：https://blog.youkuaiyun.com/qq_33291299/article/details/129087407

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本文简要介绍RocketMQ的消息消费流程，包括从服务器拉取消息，消费者消费及根据消费结果更新进度。后续将深入探讨消费的各个方面，如负载、消费模式与消息进度管理。

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2.1.2 消息消费过程

消息的消费过程，就是从服务器拉取，然后消费者进行消费，再根据业务反馈是否成功消费来推动消费进度，也就是消息的消费进度并不是保存在服务端（比如 commitlog 文件中），而是保存在消费端（可以是本地（广播模式）、broke端（集群模式））具体的代码实现：

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());

        try {
            this.makeSureStateOK();
        } catch (MQClientException e) {
            log.warn("pullMessage exception, consumer state not ok", e);
            this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_EXCEPTION);
            return;
        }

        if (this.isPause()) {
            log.warn("consumer was paused, execute pull request later. instanceName={}, group={}", this.defaultMQPushConsumer.getInstanceName(), this.defaultMQPushConsumer.getConsumerGroup());
            this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_SUSPEND);
            return;
        }

        long size = processQueue.getMsgCount().get();
        if (size > this.defaultMQPushConsumer.getPullThresholdForQueue()) {
            this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
            if ((flowControlTimes1++ % 1000) == 0) {
                log.warn(
                    "the consumer message buffer is full, so do flow control, minOffset={}, maxOffset={}, size={}, pullRequest={}, flowControlTimes={}",
                    processQueue.getMsgTreeMap().firstKey(), processQueue.getMsgTreeMap().lastKey(), size, pullRequest, flowControlTimes1);
            }
            return;
        }

        if (!this.consumeOrderly) {
            if (processQueue.getMaxSpan() > this.defaultMQPushConsumer.getConsumeConcurrentlyMaxSpan()) {
                this.executePullRequestLater(pullRequest, PULL_TIME_DELAY_MILLS_WHEN_FLOW_CONTROL);
                if ((flowControlTimes2++ % 1000) == 0) {
                    log.warn(
                        "the queue's messages, span too long, so do flow control, minOffset={}, maxOffset={}, maxSpan={}, pullRequest={}, flowControlTimes=

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