RocketMQ源码分析之Broker处理拉取消息请求（1）

最新推荐文章于 2023-01-19 17:10:19 发布

ph3636

最新推荐文章于 2023-01-19 17:10:19 发布

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分类专栏： RocketMQ 文章标签： RocketMQ

本文链接：https://blog.youkuaiyun.com/ph3636/article/details/90294000

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本文深入探讨了RocketMQ Broker如何处理拉取消息请求，涉及可读性检查、消费组与订阅信息验证、消息过滤、队列范围校验以及消息获取与过滤等多个关键步骤。通过详细分析源码，揭示了RocketMQ在消息拉取过程中的核心逻辑。

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broker处理拉取消息请求，第一次brokerAllowSuspend为true。


public RemotingCommand processRequest(final ChannelHandlerContext ctx,
    RemotingCommand request) throws RemotingCommandException {
    return this.processRequest(ctx.channel(), request, true);
}

判断当前broker是都可读，是否由消费组的订阅信息，是否可被消费

if (!PermName.isReadable(this.brokerController.getBrokerConfig().getBrokerPermission())) {
    response.setCode(ResponseCode.NO_PERMISSION);
    response.setRemark(String.format("the broker[%s] pulling message is forbidden", this.brokerController.getBrokerConfig().getBrokerIP1()));
    return response;
}

SubscriptionGroupConfig subscriptionGroupConfig =
    this.brokerController.getSubscriptionGroupManager().findSubscriptionGroupConfig(requestHeader.getConsumerGroup());
if (null == subscriptionGroupConfig) {
    response.setCode(ResponseCode.SUBSCRIPTION_GROUP_NOT_EXIST);
    response.setRemark(String.format("subscription group [%s] does not exist, %s", requestHeader.getConsumerGroup(), FAQUrl.suggestTodo(FAQUrl.SUBSCRIPTION_GROUP_NOT_EXIST)));
    return response;
}

if (!subscriptionGroupConfig.isConsumeEnable()) {
    response.setCode(ResponseCode.NO_PERMISSION);
    response.setRemark("subscription group no permission, " + requestHeader.getConsumerGroup());
    return response;
}

获取各个标志位，是否可暂停，是否提交偏移量，是否重新订阅，暂停时间

final boolean hasSuspendFlag = PullSysFlag.hasSuspendFlag(requestHeader.getSysFlag());
final boolean hasCommitOffsetFlag = PullSysFlag.hasCommitOffsetFlag(requestHeader.getSysFlag());
final boolean hasSubscriptionFlag = PullSysFlag.hasSubscriptionFlag(requestHeader.getSysFlag());

final long suspendTimeoutMillisLong = hasSuspendFlag ? requestHeader.getSuspendTimeoutMillis() : 0;

获取topic的信息，topic是否存在，是否可读，请求读取的队列id是否在可读队列的区间内，队列id从0开始。

TopicConfig topicConfig = this.brokerController.getTopicConfigManager().selectTopicConfig(requestHeader.getTopic());
if (null == topicConfig) {
    log.error("the topic {} not exist, consumer: {}", requestHeader.getTopic(), RemotingHelper.parseChannelRemoteAddr(channel));
    response.setCode(ResponseCode.TOPIC_NOT_EXIST);
    response.setRemark(String.format("topic[%s] not exist, apply first please! %s", requestHeader.getTopic(), FAQUrl.suggestTodo(FAQUrl.APPLY_TOPIC_URL)));
    return response;
}

if (!PermName.isReadable(topicConfig.getPerm())) {
    response.setCode(ResponseCode.NO_PERMISSION);
    response.setRemark("the topic[" + requestHeader.getTopic() + "] pulling message is forbidden");
    return response;
}

if (requestHeader.getQueueId() < 0 || requestHeader.getQueueId() >= topicConfig.getReadQueueNums()) {
    String errorInfo = String.format("queueId[%d] is illegal, topic:[%s] topicConfig.readQueueNums:[%d] consumer:[%s]",
        requestHeader.getQueueId(), requestHeader.getTopic(), topicConfig.getReadQueueNums(), channel.remoteAddress());
    log.warn(errorInfo);
    response.setCode(ResponseCode.SYSTEM_ERROR);
    response.setRemark(errorInfo);
    return response;
}

检查是否有消费组信息以及订阅等信息是否合法。下面的大部分校验的针对订阅的过滤表达式时非tag时的情况。


SubscriptionData subscriptionData = null;
ConsumerFilterData consumerFilterData = null;
if (hasSubscriptionFlag) {
    try {
        subscriptionData = FilterAPI.build(
            requestHeader.getTopic(), requestHeader.getSubscription(), requestHeader.getExpressionType()
        );
        if (!ExpressionType.isTagType(subscriptionData.getExpressionType())) {

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