Pulsar源码解析-客户端-消费者接收消息的底层实现

最新推荐文章于 2024-08-04 01:47:28 发布

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最新推荐文章于 2024-08-04 01:47:28 发布 · 置顶 · 1.4k 阅读

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#java #分布式 #消息队列

本文深入解析了Pulsar客户端的消费者如何接收消息，包括单个ConsumerImpl的`messageReceived`处理流程，以及MultiTopicsConsumerImpl中多个消费者协作的机制。重点讲解了`consumer.receiveAsync()`和消息确认处理，以及多消费者之间的消息传递和队列管理策略。

上一篇介绍了消费者请求拉取消息，最后发送给消费者。本章介绍消费者接收。

一、客户端消息接收入口

public class ClientCnx {
   
   

    protected void handleMessage(CommandMessage cmdMessage, ByteBuf headersAndPayload) {
   
   
        checkArgument(state == State.Ready);
        ConsumerImpl<?> consumer = consumers.get(cmdMessage.getConsumerId());
        if (consumer != null) {
   
   
            List<Long> ackSets = Collections.emptyList();
            if (cmdMessage.getAckSetsCount() > 0) {
   
   
                ackSets = new ArrayList<>(cmdMessage.getAckSetsCount());
                for (int i = 0; i < cmdMessage.getAckSetsCount(); i++) {
   
   
                    ackSets.add(cmdMessage.getAckSetAt(i));
                }
            }
            // 接收
            consumer.messageReceived(cmdMessage.getMessageId(), cmdMessage.getRedeliveryCount(), ackSets, headersAndPayload, this);
        }
    }
}

继续consumer.messageReceived

二、单个消费者ConsumerImpl接收消息处理

public class ConsumerImpl<T> {
   
   

void messageReceived(MessageIdData messageId, int redeliveryCount, List<Long> ackSet, ByteBuf headersAndPayload, ClientCnx cnx) {
   
   
        if (!verifyChecksum(headersAndPayload, messageId)) {
   
   
            // discard message with checksum error
            discardCorruptedMessage(messageId, cnx, ValidationError.ChecksumMismatch);
            return;
        }

        MessageMetadata msgMetadata;
        try {
   
   
            msgMetadata = Commands.parseMessageMetadata(headersAndPayload);
        } catch (Throwable t) {
   
   
            discardCorruptedMessage(messageId, cnx, ValidationError.ChecksumMismatch);
            return;
        }
		// 批量发送可能>1
        final int numMessages = msgMetadata.getNumMessagesInBatch();
        final int numChunks = msgMetadata.hasNumChunksFromMsg() ? msgMetadata.getNumChunksFromMsg() : 0;
        // 分块
        final boolean isChunkedMessage = numChunks > 1 && conf.getSubscriptionType() != SubscriptionType.Shared;
		
        MessageIdImpl msgId = new MessageIdImpl(messageId.getLedgerId(), messageId