Rocketmq发送之MessageQueueSelector

前言

根据自己的算法，选择MessageQueue

程序实现

SendResult sendResult = producer.send(msg, new MessageQueueSelector() {
                @Override
                public MessageQueue select(List<MessageQueue> mqs, Message msg, Object arg) {
                    Integer id = (Integer) arg;
                    int index = id % mqs.size();
                    System.out.println("id="+id+", index="+index+", mqs.size="+mqs.size());
                    return mqs.get(index);
                }
            }, orderId);

DefaultMQProducer

send

public SendResult send(Message msg, MessageQueueSelector selector, Object arg)
        throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
        msg.setTopic(withNamespace(msg.getTopic()));
        return this.defaultMQProducerImpl.send(msg, selector, arg);
    }

public SendResult send(Message msg, MessageQueueSelector selector, Object arg)
        throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
        return send(msg, selector, arg, this.defaultMQProducer.getSendMsgTimeout());
    }

sendSelectImpl

private SendResult sendSelectImpl(
        Message msg,
        MessageQueueSelector selector,
        Object arg,
        final CommunicationMode communicationMode,
        final SendCallback sendCallback, final long timeout
    ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
        long beginStartTime = System.currentTimeMillis();
        this.makeSureStateOK(); // 确保是ServiceState.RUNNING
        Validators.checkMessage(msg, this.defaultMQProducer);

        TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic()); // 本地如果不存在或不可用 从nameserver获取
        if (topicPublishInfo != null && topicPublishInfo.ok()) {
            MessageQueue mq = null;
            try {
                List<MessageQueue> messageQueueList =
                    mQClientFactory.getMQAdminImpl().parsePublishMessageQueues(topicPublishInfo.getMessageQueueList());
                Message userMessage = MessageAccessor.cloneMessage(msg);
                String userTopic = NamespaceUtil.withoutNamespace(userMessage.getTopic(), mQClientFactory.getClientConfig().getNamespace());
                userMessage.setTopic(userTopic);
                // 根据arg参数得到1个MessageQueue   selector.select 自己实现
                mq = mQClientFactory.getClientConfig().queueWithNamespace(selector.select(messageQueueList, userMessage, arg));
            } catch (Throwable e) {
                throw new MQClientException("select message queue threw exception.", e);
            }