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本文主要研究一下rocketmq的SequenceProducerImpl

SequenceProducerImpl

io/openmessaging/rocketmq/producer/SequenceProducerImpl.java

public class SequenceProducerImpl extends AbstractOMSProducer implements SequenceProducer {

    private BlockingQueue<Message> msgCacheQueue;

    public SequenceProducerImpl(final KeyValue properties) {
        super(properties);
        this.msgCacheQueue = new LinkedBlockingQueue<>();
    }

    @Override
    public KeyValue properties() {
        return properties;
    }

    @Override
    public void send(final Message message) {
        checkMessageType(message);
        org.apache.rocketmq.common.message.Message rmqMessage = OMSUtil.msgConvert((BytesMessage) message);
        try {
            Validators.checkMessage(rmqMessage, this.rocketmqProducer);
        } catch (MQClientException e) {
            throw checkProducerException(rmqMessage.getTopic(), message.headers().getString(MessageHeader.MESSAGE_ID), e);
        }
        msgCacheQueue.add(message);
    }

    @Override
    public void send(final Message message, final KeyValue properties) {
        send(message);
    }

    @Override
    public synchronized void commit() {
        List<Message> messages = new ArrayList<>();
        msgCacheQueue.drainTo(messages);

        List<org.apache.rocketmq.common.message.Message> rmqMessages = new ArrayList<>();

        for (Message message : messages) {
            rmqMessages.add(OMSUtil.msgConvert((BytesMessage) message));
        }

        if (rmqMessages.size() == 0) {
            return;
        }

        try {
            SendResult sendResult = this.rocketmqProducer.send(rmqMessages);
            String[] msgIdArray = sendResult.getMsgId().split(",");
            for (int i = 0; i < messages.size(); i++) {
                Message message = messages.get(i);
                message.headers().put(MessageHeader.MESSAGE_ID, msgIdArray[i]);
            }
        } catch (Exception e) {
            throw checkProducerException("", "", e);
        }
    }

    @Override
    public synchronized void rollback() {
        msgCacheQueue.clear();
    }
}

• 采用的是LinkedBlockingQueue，send方法实际调用的是添加到队列
• 另外提供了commit以及rollback方法，都加了synchronized保证对LinkedBlockingQueue操作的线程安全
• commit的时候，将queue的数据drainTo到list，然后批量发送；rollback的时候清空整个LinkedBlockingQueue

小结

rocketmq的SequenceProducerImpl在send方法的时候不是真正方法，而是添加到队列，只有在commit的时候才批量发送，rollback的时候清空队列。这里的send方法语义不是太好，可以改为pending之类的名称。

doc

• SequenceProducerImpl