生产端 Confirm 消息确认机制

消息的确认，是指生产者投递消息后，如果 Broker 收到消息，则会给我们生产者一个应答。生产者进行接收应答，用来确定这条消息是否正常的发送到 Broker ，这种方式也是消息的可靠性投递的核心保障!

Confirm 确认机制流程图

如何实现Confirm确认消息?

第一步:在 channel 上开启确认模式: channel.confirmSelect()

第二步:在 channel 上添加监听: channel.addConfirmListener(ConfirmListener listener);, 监听成功和失败的返回结果，根据具体的结果对消息进行重新发送、或记录日志等后续处理!

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.ConfirmListener;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;

public class ConfirmProducer {

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

Connection connection = factory.newConnection();

Channel channel = connection.createChannel();

String exchangeName = "test_confirm_exchange";

String routingKey = "item.update";

//指定消息的投递模式：confirm 确认模式

channel.confirmSelect();

//发送

final long start = System.currentTimeMillis();

for (int i = 0; i < 5 ; i++) {

String msg = "this is confirm msg ";

channel.basicPublish(exchangeName, routingKey, null, msg.getBytes());

System.out.println("Send message : " + msg);

}

//添加一个确认监听， 这里就不关闭连接了，为了能保证能收到监听消息

channel.addConfirmListener(new ConfirmListener() {

/**

* 返回成功的回调函数

*/

public void handleAck(long deliveryTag, boolean multiple) throws IOException {

System.out.println("succuss ack");

System.out.println(multiple);

System.out.println("耗时：" + (System.currentTimeMillis() - start) + "ms");

}

/**

* 返回失败的回调函数

*/

public void handleNack(long deliveryTag, boolean multiple) throws IOException {

System.out.printf("defeat ack");

System.out.println("耗时：" + (System.currentTimeMillis() - start) + "ms");

}

});

}

}

import com.rabbitmq.client.*;

import java.io.IOException;

public class ConfirmConsumer {

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

factory.setAutomaticRecoveryEnabled(true);

factory.setNetworkRecoveryInterval(3000);

Connection connection = factory.newConnection();

Channel channel = connection.createChannel();

String exchangeName = "test_confirm_exchange";

String queueName = "test_confirm_queue";

String routingKey = "item.#";

channel.exchangeDeclare(exchangeName, "topic", true, false, null);

channel.queueDeclare(queueName, false, false, false, null);

//一般不用代码绑定，在管理界面手动绑定

channel.queueBind(queueName, exchangeName, routingKey);

//创建消费者并接收消息

Consumer consumer = new DefaultConsumer(channel) {

@Override

public void handleDelivery(String consumerTag, Envelope envelope,

AMQP.BasicProperties properties, byte[] body)

throws IOException {

String message = new String(body, "UTF-8");

System.out.println(" [x] Received '" + message + "'");

}

};

//设置 Channel 消费者绑定队列

channel.basicConsume(queueName, true, consumer);

}

}

我们此处只关注生产端输出消息

Send message : this is confirm msg

Send message : this is confirm msg

Send message : this is confirm msg

Send message : this is confirm msg

Send message : this is confirm msg

succuss ack

true

耗时：3ms

succuss ack

true

耗时：4ms

注意事项

我们采用的是异步 confirm 模式：提供一个回调方法，服务端 confirm 了一条或者多条消息后 Client 端会回调这个方法。除此之外还有单条同步 confirm 模式、批量同步 confirm 模式，由于现实场景中很少使用我们在此不做介绍，如有兴趣直接参考官方文档。

我们运行生产端会发现每次运行结果都不一样,会有多种情况出现，因为 Broker 会进行优化，有时会批量一次性 confirm ，有时会分开几条 confirm。

succuss ack

true

耗时：3ms

succuss ack

false

耗时：4ms

或者

succuss ack

true

耗时：3ms

Return 消息机制

Return Listener 用于处理一-些不可路 由的消息!

消息生产者，通过指定一个 Exchange 和 Routingkey，把消息送达到某一个队列中去，然后我们的消费者监听队列，进行消费处理操作!

但是在某些情况下，如果我们在发送消息的时候，当前的 exchange 不存在或者指定的路由 key 路由不到，这个时候如果我们需要监听这种不可达的消息，就要使用 Return Listener !

在基础API中有一个关键的配置项:Mandatory：如果为 true，则监听器会接收到路由不可达的消息，然后进行后续处理，如果为 false，那么 broker 端自动删除该消息!

Return 消息机制流程图

Return 消息示例

首先我们需要发送三条消息，并且故意将第 0 条消息的 routing Key设置为错误的，让他无法正常路由到消费端。

mandatory 设置为 true 路由不可达的消息会被监听到，不会被自动删除.即channel.basicPublish(exchangeName, errRoutingKey, true,null, msg.getBytes());

最后添加监听即可监听到不可路由到消费端的消息channel.addReturnListener(ReturnListener r))

import com.rabbitmq.client.*;

import java.io.IOException;

public class ReturnListeningProducer {

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

Connection connection = factory.newConnection();

Channel channel = connection.createChannel();

String exchangeName = "test_return_exchange";

String routingKey = "item.update";

String errRoutingKey = "error.update";

//指定消息的投递模式：confirm 确认模式

channel.confirmSelect();

//发送

for (int i = 0; i < 3 ; i++) {

String msg = "this is return——listening msg ";

//@param mandatory 设置为 true 路由不可达的消息会被监听到，不会被自动删除

if (i == 0) {

channel.basicPublish(exchangeName, errRoutingKey, true,null, msg.getBytes());

} else {

channel.basicPublish(exchangeName, routingKey, true, null, msg.getBytes());

}

System.out.println("Send message : " + msg);

}

//添加一个确认监听， 这里就不关闭连接了，为了能保证能收到监听消息

channel.addConfirmListener(new ConfirmListener() {

/**

* 返回成功的回调函数

*/

public void handleAck(long deliveryTag, boolean multiple) throws IOException {

System.out.println("succuss ack");

}

/**

* 返回失败的回调函数

*/

public void handleNack(long deliveryTag, boolean multiple) throws IOException {

System.out.printf("defeat ack");

}

});

//添加一个 return 监听

channel.addReturnListener(new ReturnListener() {

public void handleReturn(int replyCode, String replyText, String exchange, String routingKey, AMQP.BasicProperties properties, byte[] body) throws IOException {

System.out.println("return relyCode: " + replyCode);

System.out.println("return replyText: " + replyText);

System.out.println("return exchange: " + exchange);

System.out.println("return routingKey: " + routingKey);

System.out.println("return properties: " + properties);

System.out.println("return body: " + new String(body));

}

});

}

}

import com.rabbitmq.client.*;

import java.io.IOException;

public class ReturnListeningConsumer {

public static void main(String[] args) throws Exception {

//1. 创建一个 ConnectionFactory 并进行设置

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

factory.setAutomaticRecoveryEnabled(true);

factory.setNetworkRecoveryInterval(3000);

//2. 通过连接工厂来创建连接

Connection connection = factory.newConnection();

//3. 通过 Connection 来创建 Channel

Channel channel = connection.createChannel();

//4. 声明

String exchangeName = "test_return_exchange";

String queueName = "test_return_queue";

String routingKey = "item.#";

channel.exchangeDeclare(exchangeName, "topic", true, false, null);

channel.queueDeclare(queueName, false, false, false, null);

//一般不用代码绑定，在管理界面手动绑定

channel.queueBind(queueName, exchangeName, routingKey);

//5. 创建消费者并接收消息

Consumer consumer = new DefaultConsumer(channel) {

@Override

public void handleDelivery(String consumerTag, Envelope envelope,

AMQP.BasicProperties properties, byte[] body)

throws IOException {

String message = new String(body, "UTF-8");

System.out.println(" [x] Received '" + message + "'");

}

};

//6. 设置 Channel 消费者绑定队列

channel.basicConsume(queueName, true, consumer);

}

}

我们只关注生产端结果，消费端只收到两条消息。

Send message : this is return——listening msg

Send message : this is return——listening msg

Send message : this is return——listening msg

return relyCode: 312

return replyText: NO_ROUTE

return exchange: test_return_exchange

return routingKey: error.update

return properties: #contentHeader(content-type=null, content-encoding=null, headers=null, delivery-mode=null, priority=null, correlation-id=null, reply-to=null, expiration=null, message-id=null, timestamp=null, type=null, user-id=null, app-id=null, cluster-id=null)

return body: this is return——listening msg

succuss ack

succuss ack

succuss ack

消费端 Ack 和 Nack 机制

消费端进行消费的时候，如果由于业务异常我们可以进行日志的记录，然后进行补偿!如果由于服务器宕机等严重问题，那我们就需要手工进行ACK保障消费端消费成功!消费端重回队列是为了对没有处理成功的消息，把消息重新会递给Broker!一般我们在实际应用中，都会关闭重回队列，也就是设置为False。

参考 api

void basicNack(long deliveryTag, boolean multiple, boolean requeue) throws IOException;

void basicAck(long deliveryTag, boolean multiple) throws IOException;

如何设置手动 Ack 、Nack 以及重回队列

首先我们发送五条消息，将每条消息对应的循环下标 i 放入消息的 properties 中作为标记，以便于我们在后面的回调方法中识别。

其次， 我们将消费端的 ·channel.basicConsume(queueName, false, consumer); 中的 autoAck属性设置为 false，如果设置为true的话 将会正常输出五条消息。

我们通过 Thread.sleep(2000)来延时一秒，用以看清结果。我们获取到properties中的num之后，通过channel.basicNack(envelope.getDeliveryTag(), false, true);将 num为0的消息设置为 nack，即消费失败，并且将 requeue属性设置为true，即消费失败的消息重回队列末端。

import com.rabbitmq.client.*;

import java.util.HashMap;

import java.util.Map;

public class AckAndNackProducer {

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

Connection connection = factory.newConnection();

Channel channel = connection.createChannel();

String exchangeName = "test_ack_exchange";

String routingKey = "item.update";

String msg = "this is ack msg";

for (int i = 0; i < 5; i++) {

Map headers = new HashMap();

headers.put("num" ,i);

AMQP.BasicProperties properties = new AMQP.BasicProperties().builder()

.deliveryMode(2)

.headers(headers)

.build();

String tem = msg + ":" + i;

channel.basicPublish(exchangeName, routingKey, true, properties, tem.getBytes());

System.out.println("Send message : " + msg);

}

channel.close();

connection.close();

}

}

import com.rabbitmq.client.*;

import java.io.IOException;

public class AckAndNackConsumer {

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

factory.setVirtualHost("/");

factory.setUsername("guest");

factory.setPassword("guest");

factory.setAutomaticRecoveryEnabled(true);

factory.setNetworkRecoveryInterval(3000);

Connection connection = factory.newConnection();

final Channel channel = connection.createChannel();

String exchangeName = "test_ack_exchange";

String queueName = "test_ack_queue";

String routingKey = "item.#";

channel.exchangeDeclare(exchangeName, "topic", true, false, null);

channel.queueDeclare(queueName, false, false, false, null);

//一般不用代码绑定，在管理界面手动绑定

channel.queueBind(queueName, exchangeName, routingKey);

Consumer consumer = new DefaultConsumer(channel) {

@Override

public void handleDelivery(String consumerTag, Envelope envelope,

AMQP.BasicProperties properties, byte[] body)

throws IOException {

String message = new String(body, "UTF-8");

System.out.println(" [x] Received '" + message + "'");

try {

Thread.sleep(2000);

} catch (InterruptedException e) {

e.printStackTrace();

}

if ((Integer) properties.getHeaders().get("num") == 0) {

channel.basicNack(envelope.getDeliveryTag(), false, true);

} else {

channel.basicAck(envelope.getDeliveryTag(), false);

}

}

};

//6. 设置 Channel 消费者绑定队列

channel.basicConsume(queueName, false, consumer);

}

}

我们此处只关心消费端输出，可以看到第 0 条消费失败重新回到队列尾部消费。

[x] Received 'this is ack msg:1'

[x] Received 'this is ack msg:2'

[x] Received 'this is ack msg:3'

[x] Received 'this is ack msg:4'

[x] Received 'this is ack msg:0'

[x] Received 'this is ack msg:0'

[x] Received 'this is ack msg:0'

[x] Received 'this is ack msg:0'

[x] Received 'this is ack msg:0'