Pulsar源码解析-客户端-单个消费者ConsumerImpl创建底层实现

pulsar消费者有多种
ConsumerImpl：一个消费者客户端连接
MultiTopicsConsumerImpl：多个消费者，topic配置有多个，如果开启重试队列也是当前实现，具体看MultiTopicsConsumerImpl源码解析
PatternMultiTopicsConsumerImpl：配置正则表达式的topic，本质也是MultiTopicsConsumerImpl，主要实现了topic的自动发现。
ZeroQueueConsumerImpl：没有缓冲队列的消费者 即receiverQueueSize=0

本篇介绍的是相对最好理解的ConsumerImpl，创建方式：

Consumer subscribe = PulsarClient.builder()
             	.serviceUrl("pulsar://127.0.0.1:6650")
             	.build()
              	.newConsumer()
                .topic("public/default/topic")
                .enableRetry(false)
                ...

重点是：topic(...)只配一个，enableRetry(fasle)

之前介绍过生产者的创建，入口是PulsarClientImpl，消费者也是这里。

消费者的介绍跟以前一样，省略参数校验，日志等代码

一、客户端ConsumerImpl创建入口

public class PulsarClientImpl {
   
   

public <T> CompletableFuture<Consumer<T>> subscribeAsync(ConsumerConfigurationData<T> conf, Schema<T> schema, ConsumerInterceptors<T> interceptors) {
   
   
        // 配置的正则
        if (conf.getTopicsPattern() != null) {
   
   
            return patternTopicSubscribeAsync(conf, schema, interceptors);
        } 
      	// 单个消费者
		else if (conf.getTopicNames().size() == 1) {
   
   
            return singleTopicSubscribeAsync(conf, schema, interceptors);
        } 
        // 多个
        else {
   
   
            return multiTopicSubscribeAsync(conf, schema, interceptors);
        }
    }
}

singleTopicSubscribeAsync(...)中先处理schema，然后调用了doSingleTopicSubscribeAsync(...)
直接看 doSingleTopicSubscribeAsync(...)

public class PulsarClientImpl {
   
   

    private <T> CompletableFuture<Consumer<T>> doSingleTopicSubscribeAsync(ConsumerConfigurationData<T> conf, Schema<T> schema, ConsumerInterceptors<T> interceptors) {
   
   
    
        CompletableFuture<Consumer<T>> consumerSubscribedFuture = new CompletableFuture<>();

        String topic = conf.getSingleTopic();
        // 获取分区数
        getPartitionedTopicMetadata(topic).thenAccept(metadata -> {
   
   
            ConsumerBase<T> consumer;
			// 如果是分区topic
            if (metadata.partitions > 0) {
   
   
            	// 多个分区创建MultiTopicsConsumerImpl
            	// 当前方法doSingle命名是不是不太准确...我也想不出更好的命名了
                consumer = MultiTopicsConsumerImpl.createPartitionedConsumer(PulsarClientImpl.this, conf,
                        externalExecutorProvider, consumerSubscribedFuture, metadata.partitions, schema, interceptors);
            } else {
   
   
            	// 非分区topic，partitionIndex是-1
                int partitionIndex = TopicName.getPartitionIndex(topic);
                consumer = ConsumerImpl.newConsumerImpl(PulsarClientImpl.this, topic, conf, externalExecutorProvider,
                        partitionIndex, false, consumerSubscribedFuture, null, schema, interceptors,
                        true);
            }
            consumers.add(consumer);
        }).exceptionally(ex -> {
   
   
            return null;
        });

        return consumerSubscribedFuture;
    }
}

继续ConsumerImpl.newConsumerImpl(...)

二、ConsumerImpl构造

public