RabbitMQ消息确认(发送确认,接收确认)

消息确认

每个 Consumer 可能需要一段时间才能处理完收到的数据。如果在这个过程中，Consumer 出错或异常退出，而数据还没有处理完成，那么这段数据就丢失了。因为我们采用 no-ack 的方式进行确认，也就是说，每次 Consumer 接到数据后，不管是否处理完成，RabbitMQ Server 会立即把这个 Message 标记为完成，然后从 Queue 中删除。

为了保证数据不被丢失，RabbitMQ 支持消息确认机制，这种机制下不能采用 no-ack，而应该是在处理完数据后发送 ack。如果处理中途 Consumer 退出了，但是没有发送 ack，那么 RabbitMQ 就会把这个 Message 发送到下一个 Consumer，这样就保证了在 Consumer 异常退出的情况下数据也不会丢失。

这里并没有用到超时机制，RabbitMQ 仅仅通过 Consumer 的连接中断来确认该 Message 并没有被正确处理，也就是说，RabbitMQ 给 Consumer 足够长的时间来做数据处理。

之前的例子中，这就是消息确认机制的应用，这种情况下，即使中断任务执行，也不会影响 RabbitMQ 中消息的处理，RabbitMQ 会将其发送给下一个 Consumer 进行处理。

如果忘记了 ack，那么后果很严重。当 Consumer 退出时，Message 会重新分发。然后 RabbitMQ 会占用越来越多的内存，由于 RabbitMQ 会长时间运行，因此这个“内存泄漏”是致命的。针对这行场景，可以通过以下命令进行 debug：

sudo rabbitmqctl list_queues name messages_ready messages_unacknowledged

消息持久化

为了保证在 RabbitMQ 退出或者 crash 了数据不丢失，需要将 Queue 和 Message 持久化。

使用spring的代码示例

下面是一个使用spring整合的代码示例:

首先是rabbitmq的配置文件:

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:rabbit="http://www.springframework.org/schema/rabbit"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/rabbit
http://www.springframework.org/schema/rabbit/spring-rabbit-1.4.xsd">
<bean id="jsonMessageConverter" class="org.springframework.amqp.support.converter.Jackson2JsonMessageConverter" />
<rabbit:connection-factory
id="connectionFactory"
host="${rabbit.host}"
port="${rabbit.port}"
username="${rabbit.username}"
password="${rabbit.password}"
publisher-confirms="true"
/>
<rabbit:admin connection-factory="connectionFactory" />
<rabbit:template id="amqpTemplate" connection-factory="connectionFactory"
confirm-callback="confirmCallBackListener"
return-callback="returnCallBackListener"
mandatory="true"
/>
<rabbit:queue name="CONFIRM_TEST" />
<rabbit:direct-exchange name="DIRECT_EX" id="DIRECT_EX" >
<rabbit:bindings>
<rabbit:binding queue="CONFIRM_TEST" />
</rabbit:bindings>
</rabbit:direct-exchange>
<rabbit:listener-container
connection-factory="connectionFactory" acknowledge="manual" >
<rabbit:listener queues="CONFIRM_TEST" ref="receiveConfirmTestListener" />
</rabbit:listener-container>
</beans>

然后发送方:

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import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service("publishService")
public class PublishService {
@Autowired
private AmqpTemplate amqpTemplate;
public void send(String exchange, String routingKey, Object message) {
amqpTemplate.convertAndSend(exchange, routingKey, message);
}
}

消费方:

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import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.core.ChannelAwareMessageListener;
import org.springframework.stereotype.Service;
import com.rabbitmq.client.Channel;
@Service("receiveConfirmTestListener")
public class ReceiveConfirmTestListener implements ChannelAwareMessageListener {
@Override
public void onMessage(Message message, Channel channel) throws Exception {
try{
System.out.println("consumer--:"+message.getMessageProperties()+":"+new String(message.getBody()));
channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);
}catch(Exception e){
e.printStackTrace();//TODO 业务处理
channel.basicNack(message.getMessageProperties().getDeliveryTag(), false,false);
}
}
}

确认后回调:

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import org.springframework.amqp.rabbit.core.RabbitTemplate.ConfirmCallback;
import org.springframework.amqp.rabbit.support.CorrelationData;
import org.springframework.stereotype.Service;
@Service("confirmCallBackListener")
public class ConfirmCallBackListener implements ConfirmCallback{
@Override
public void confirm(CorrelationData correlationData, boolean ack, String cause) {
System.out.println("confirm--:correlationData:"+correlationData+",ack:"+ack+",cause:"+cause);
}
}

失败后return回调:

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import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.core.RabbitTemplate.ReturnCallback;
import org.springframework.stereotype.Service;
@Service("returnCallBackListener")
public class ReturnCallBackListener implements ReturnCallback{
@Override
public void returnedMessage(Message message, int replyCode, String replyText, String exchange, String routingKey) {
System.out.println("return--message:"+new String(message.getBody())+",replyCode:"+replyCode+",replyText:"+replyText+",exchange:"+exchange+",routingKey:"+routingKey);
}
}

测试类:

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import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import com.dingcheng.confirms.publish.PublishService;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"classpath:application-context.xml"})
public class TestConfirm {
@Autowired
private PublishService publishService;
private static String exChange = "DIRECT_EX";
@Test
public void test1() throws InterruptedException{
String message = "currentTime:"+System.currentTimeMillis();
System.out.println("test1---message:"+message);
//exchange,queue 都正确,confirm被回调, ack=true
publishService.send(exChange,"CONFIRM_TEST",message);
Thread.sleep(1000);
}
@Test
public void test2() throws InterruptedException{
String message = "currentTime:"+System.currentTimeMillis();
System.out.println("test2---message:"+message);
//exchange 错误,queue 正确,confirm被回调, ack=false
publishService.send(exChange+"NO","CONFIRM_TEST",message);
Thread.sleep(1000);
}
@Test
public void test3() throws InterruptedException{
String message = "currentTime:"+System.currentTimeMillis();
System.out.println("test3---message:"+message);
//exchange 正确,queue 错误 ,confirm被回调, ack=true; return被回调 replyText:NO_ROUTE
publishService.send(exChange,"",message);
// Thread.sleep(1000);
}
@Test
public void test4() throws InterruptedException{
String message = "currentTime:"+System.currentTimeMillis();
System.out.println("test4---message:"+message);
//exchange 错误,queue 错误,confirm被回调, ack=false
publishService.send(exChange+"NO","CONFIRM_TEST",message);
Thread.sleep(1000);
}
}

测试结果:

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test1---message:currentTime:1483786948506
test2---message:currentTime:1483786948532
consumer--:MessageProperties [headers={spring_return_correlation=445bc7ca-a5bd-47e2-8ba3-f0448420e441}, timestamp=null, messageId=null, userId=null, appId=null, clusterId=null, type=null, correlationId=null, replyTo=null, contentType=text/plain, contentEncoding=UTF-8, contentLength=0, deliveryMode=PERSISTENT, expiration=null, priority=0, redelivered=false, receivedExchange=DIRECT_EX, receivedRoutingKey=CONFIRM_TEST, deliveryTag=1, messageCount=0]:currentTime:1483786948506
test3---message:currentTime:1483786948536
confirm--:correlationData:null,ack:false,cause:channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'DIRECT_EXNO' in vhost '/', class-id=60, method-id=40)
confirm--:correlationData:null,ack:false,cause:Channel closed by application
[ERROR] 2017-01-07 19:02:28 org.springframework.amqp.rabbit.connection.CachingConnectionFactory.shutdownCompleted(CachingConnectionFactory.java:281):--> Channel shutdown: channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'DIRECT_EXNO' in vhost '/', class-id=60, method-id=40)
return--message:currentTime:1483786948536,replyCode:312,replyText:NO_ROUTE,exchange:DIRECT_EX,routingKey:
confirm--:correlationData:null,ack:true,cause:null
test4---message:currentTime:1483786948546
confirm--:correlationData:null,ack:false,cause:channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'DIRECT_EXNO' in vhost '/', class-id=60, method-id=40)
[ERROR] 2017-01-07 19:02:28 org.springframework.amqp.rabbit.connection.CachingConnectionFactory.shutdownCompleted(CachingConnectionFactory.java:281):--> Channel shutdown: channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'DIRECT_EXNO' in vhost '/', class-id=60, method-id=40)

代码和配置里面,已经都有注释,就不在多说明了.(callback是异步的,所以测试中sleep1秒钟等待下)

总结下就是:

如果消息没有到exchange,则confirm回调,ack=false

如果消息到达exchange,则confirm回调,ack=true

exchange到queue成功,则不回调return

exchange到queue失败,则回调return(需设置mandatory=true,否则不回回调,消息就丢了)

备注:需要说明,spring-rabbit和原生的rabbit-client ,表现是不一样的.

测试的时候,原生的client,exchange错误的话,直接就报错了,是不会到confirmListener和returnListener的

源码地址:https://github.com/qq315737546/spring-rabbit