【RabbitMQ】6、rabbitmq生产者的消息确认

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　　通过Publisher Confirms and Returns机制，生产者可以判断消息是否发送到了exchange及queue，而通过消费者确认机制，Rabbitmq可以决定是否重发消息给消费者，以保证消息被处理。

1.什么是Publisher Confirms and Returns？
　　Delivery processing acknowledgements from consumers to RabbitMQ are known as acknowledgements in AMQP 0-9-1 parlance; broker acknowledgements to publishers are a protocol extension called publisher confirms.
地址：http://www.rabbitmq.com/confirms.html
　　根据RabbitMq官网定义，rabbitmq代理(broker)对发布者(publishers)的确认被称作发布者确认(publisher confirms)，这种机制是Rabbitmq对标准Amqp协议的扩展。因此通过这种机制可以确认消息是否发送给了目标。

2.如何通过Spring amqp来使用Publisher Confirms and Returns机制？
　　Confirmed and returned messages are supported by setting the CachingConnectionFactory’s publisherConfirms and publisherReturns properties to ‘true’ respectively.When these options are set, Channel s created by the factory are wrapped in an PublisherCallbackChannel, which is used to facilitate the callbacks. When such a channel is obtained, the client can register a PublisherCallbackChannel.Listener with the Channel. The PublisherCallbackChannel implementation contains logic to route a confirm/return to the appropriate listener. These features are explained further in the following sections.
http://docs.spring.io/spring-amqp/docs/1.6.3.RELEASE/reference/html/_reference.html#cf-pub-conf-ret
　　通过Spring amqp文档可以看到，要使用这种机制需要将Template模版的设publisherConfirms 或publisherReturns 属性设置为true，此外ConnectionFactory要配置为CachingConnectionFactory。



    <bean id="connectionFactory"
class="org.springframework.amqp.rabbit.connection.CachingConnectionFactory">
<property name="host" value="192.168.2.133" />
<property name="port" value="5672" />
<property name="username" value="sun" />
<property name="password" value="123456" />
<property name="publisherConfirms" value="true" />
<property name="publisherReturns" value="true" />
</bean>
2.1 ConfirmCallback的使用及触发的一种场景



import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.support.CorrelationData;
import org.springframework.stereotype.Service;
/**
* @author wangzhongqiu
*         Created on 2017/10/31.
* @description:继承RabbitTemplate.ConfirmCallback,消息确认监听器
*/
@Service
public class ConfirmCallBackListener implements RabbitTemplate.ConfirmCallback {
private Logger log = LoggerFactory.getLogger(CommonProducer.class);
@Override
public void confirm(CorrelationData correlationData, boolean ack, String cause) {
log.info("收到回调，成功发送到broker");
}
}
　　使用场景：

2.2 ReturnCallback的使用及触发的一种场景



import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.stereotype.Service;
/**
* @author wangzhongqiu
*         Created on 2017/10/31.
* @description:继承RabbitTemplate.ReturnCallback,消息发送失败返回监听器
*/
@Service
public class ReturnCallBackListener implements RabbitTemplate.ReturnCallback {
private Logger log = LoggerFactory.getLogger(CommonProducer.class);
@Override
public void returnedMessage(Message message, int replyCode, String replyText, String exchange, String routingKey) {
log.info("收到回调");
log.info("return--message:" + new String(message.getBody()) + ",replyCode:" + replyCode + ",replyText:" + replyText + ",exchange:" + exchange + ",routingKey:" + routingKey);
}
}
　　使用场景：