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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<>();}@Overridepublic KeyValue properties() {return properties;}@Overridepublic 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);}@Overridepublic void send(final Message message, final KeyValue properties) {send(message);}@Overridepublic 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);}}@Overridepublic 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