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消费端限流

什么是消费端的限流？

假设一个场景，首先，我们RabbitMQ服务器有上万条未处理的消息，我们随便打开一个消费者客户端，会出现下面情况：

巨量的消息瞬间全部推送过来，但是我们单个客户端无法同时处理这么多数据！

消费端限流RabbitMQ提供的解决方案

RabbitMQ提供了一种qos（服务质量保证）功能，即在非自动确认消息的前提下，如果一定数目的消息（通过基于Consumer或者Channel设置Qos的值）未被确认前，不进行消费新的消息

Void BasicQos(uint prefetchSize, ushort prefetchCount, bool global);

prefetchSize：0 不限制消息大小

prefetchSize：会告诉RabbitMQ不要同时给一个消费者推送多于N个消息，即一旦有N个消息还没有ack，则该Consumer将block（阻塞）掉，直到有消息ack

Global：true\false是否将上面设置应用于Channel；简单来说，就是上面限制是Channel级别的还是Consumer级别

注意：

prefetchSize和global这两项，RabbitMQ没有实现，暂且不研究；

prefetch_count在no_ask=false的情况下生效，即在自动应答的情况下，这两个值是不生效的；

代码演示

package com.zxp.rabbitmqapi.limit;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.DefaultConsumer;import com.rabbitmq.client.Envelope;import java.io.IOException;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 8:59 */public class  MyConsumer extends DefaultConsumer {    private Channel channel ;    public MyConsumer(Channel channel) {        super(channel);        this.channel = channel;    }    @Override    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {        System.err.println("-----------consume message----------");        System.err.println("consumerTag: " + consumerTag);        System.err.println("envelope: " + envelope);        System.err.println("properties: " + properties);        System.err.println("body: " + new String(body));        channel.basicAck(envelope.getDeliveryTag(), false);    }}

消费端代码

package com.zxp.rabbitmqapi.limit;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:01 */public class Consumer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        String exchangeName = "test_qos_exchange";        String queueName = "test_qos_queue";        String routingKey = "qos.#";        channel.exchangeDeclare(exchangeName, "topic", true, false, null);        channel.queueDeclare(queueName, true, false, false, null);        channel.queueBind(queueName, exchangeName, routingKey);        //1 限流方式  第一件事就是 autoAck设置为 false        channel.basicQos(0, 1, false);        channel.basicConsume(queueName, false, new MyConsumer(channel));    }}

提供方代码

package com.zxp.rabbitmqapi.limit;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:01 */public class Producer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        String exchange = "test_qos_exchange";        String routingKey = "qos.save";        String msg = "Hello RabbitMQ QOS Message";        for(int i =0; i<5; i ++){            channel.basicPublish(exchange, routingKey, true, null, msg.getBytes());        }    }}

消息的ACK与重回队列

消费端手工ACK与NACK

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，那么我们就需要手工进行ACK，保障消费端消费成功！

消费端的重回队列

消费端重回队列是为了对没有处理成功的消息，把消息重新回递给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；因为重回队列消息有很大概率依然会处理失败！

代码演示

package com.zxp.rabbitmqapi.ack;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.DefaultConsumer;import com.rabbitmq.client.Envelope;import java.io.IOException;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:15 */public class MyConsumer extends DefaultConsumer {    private Channel channel ;    public MyConsumer(Channel channel) {        super(channel);        this.channel = channel;    }    @Override    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {        System.err.println("-----------consume message----------");        System.err.println("body: " + new String(body));        try {            Thread.sleep(2000);        } catch (InterruptedException e) {            e.printStackTrace();        }        if((Integer)properties.getHeaders().get("num") == 0) {            System.err.println("模拟第三方接口调用失败。。。。");//            手动签收，重回队列            channel.basicNack(envelope.getDeliveryTag(), false, true);        } else {            channel.basicAck(envelope.getDeliveryTag(), false);        }    }}

package com.zxp.rabbitmqapi.ack;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:16 */public class Consumer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        String exchangeName = "test_ack_exchange";        String queueName = "test_ack_queue";        String routingKey = "ack.#";        channel.exchangeDeclare(exchangeName, "topic", true, false, null);        channel.queueDeclare(queueName, true, false, false, null);        channel.queueBind(queueName, exchangeName, routingKey);        // 手工签收 必须要关闭 autoAck = false        channel.basicConsume(queueName, false, new MyConsumer(channel));    }}

package com.zxp.rabbitmqapi.ack;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;import java.util.HashMap;import java.util.Map;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:18 */public class Producer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        String exchange = "test_ack_exchange";        String routingKey = "ack.save";        for(int i =0; i<5; i ++){            Map
   
     headers = new HashMap
    
     ();            headers.put("num", i);            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()                    .deliveryMode(2)                    .contentEncoding("UTF-8")                    .headers(headers)                    .build();            String msg = "Hello RabbitMQ ACK Message " + i;            channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());        }    }}
    
   

TTL消息

TTL是Time To Live的缩写，也就是生存时间

RabbitMQ支持消息的过期时间，在消息发送时可以进行指定

RabbitMQ支持队列的过期时间，从消息入队列开始计算，只要超过了队列的超时时间配置，那么消息自动的清除

纯控制台操作（演示TTL队列消息特点）

针对队列，只要是这个队列的消息，就只有这么长的存活时间

注意：主要针对消息设置，跟交换机、队列、消费者设置毫无关系

代码演示

package com.zxp.rabbitmqapi.ttl;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;import com.rabbitmq.client.QueueingConsumer;import java.util.Map;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:29 */public class Consumer {    public static void main(String[] args) throws Exception {        //1 创建一个ConnectionFactory, 并进行配置        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        //2 通过连接工厂创建连接        Connection connection = connectionFactory.newConnection();        //3 通过connection创建一个Channel        Channel channel = connection.createChannel();        //4 声明（创建）一个队列        String queueName = "test001";        channel.queueDeclare(queueName, true, false, false, null);        //5 创建消费者        QueueingConsumer queueingConsumer = new QueueingConsumer(channel);        //6 设置Channel        channel.basicConsume(queueName, true, queueingConsumer);        while(true){            //7 获取消息            QueueingConsumer.Delivery delivery = queueingConsumer.nextDelivery();            String msg = new String(delivery.getBody());            System.err.println("消费端: " + msg);            Map
   
     headers = delivery.getProperties().getHeaders();            System.err.println("headers get my1 value: " + headers.get("my1"));            //Envelope envelope = delivery.getEnvelope();        }    }}
   

package com.zxp.rabbitmqapi.ttl;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;import java.util.HashMap;import java.util.Map;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:30 */public class Procuder {    public static void main(String[] args) throws Exception {        //1 创建一个ConnectionFactory, 并进行配置        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        //2 通过连接工厂创建连接        Connection connection = connectionFactory.newConnection();        //3 通过connection创建一个Channel        Channel channel = connection.createChannel();        Map
   
     headers = new HashMap<>();        headers.put("my1", "111");        headers.put("my2", "222");        AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()                .deliveryMode(2)                .contentEncoding("UTF-8")                .expiration("10000")                .headers(headers)                .build();        //4 通过Channel发送数据        for(int i=0; i < 5; i++){            String msg = "Hello RabbitMQ!";            //1 exchange   2 routingKey            channel.basicPublish("", "test001", properties, msg.getBytes());        }        //5 记得要关闭相关的连接        channel.close();        connection.close();    }}
   

死信队列

死信队列：DLX，Dead-Letter-Exchange

利用DLX，当消息在一个队列中变成死信（dead message）之后，它能被重新publish到另一个Exchange，这个Exchange就是DLX

消息变成死信有以下几种情况

1.消息被拒绝（basic.reject/basic.nack）并且requeue=false

2.消息TTL过期

3.队列达到最大长度

死信队列的特点

1.DLX也是一个正常的Exchange，和一般的Exchange没有区别，它能在任何的队列上被指定，实际上就是设置某个队列的属性；

2.当这个队列中有死信时，RabbitMQ就会自动的将这个消息重新发布到设置的Exchange上去，进而被路由到另一个队列；

3.可以监听这个队列中消息做相应的处理，这个特性可以弥补RabbitMQ3.0以前支持的immediate参数的功能；

死信队列设置

1.首先需要设置死信队列的Exchange和Queue，然后进行绑定：

Exchange：dlx.exchange

Queue：dlx.queue

RoutingKey：#

2.然后我们进行正常声明交换机、队列、绑定，只不过我们需要在队列加上一个参数即可：

Arguments.put(“x-dead-letter-exchange”,”dlx.exchange”)；

3.这样消息在过期、requeue、队列在达到最大长度时，消息就可以直接路由到死信队列！

代码演示

package com.zxp.rabbitmqapi.dlx;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.DefaultConsumer;import com.rabbitmq.client.Envelope;import java.io.IOException;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 9:59 * 自定义消费端 */public class MyConsumer extends DefaultConsumer {    public MyConsumer(Channel channel) {        super(channel);    }    @Override    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {        System.err.println("-----------consume message----------");        System.err.println("consumerTag: " + consumerTag);        System.err.println("envelope: " + envelope);        System.err.println("properties: " + properties);        System.err.println("body: " + new String(body));    }}

package com.zxp.rabbitmqapi.dlx;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;import java.util.HashMap;import java.util.Map;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 10:00 * 消费端 */public class Consumer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        // 这就是一个普通的交换机 和 队列 以及路由        String exchangeName = "test_dlx_exchange";        String routingKey = "dlx.#";        String queueName = "test_dlx_queue";        channel.exchangeDeclare(exchangeName, "topic", true, false, null);        Map
   
     agruments = new HashMap
    
     ();        agruments.put("x-dead-letter-exchange", "dlx.exchange");        //这个agruments属性，要设置到声明队列上        channel.queueDeclare(queueName, true, false, false, agruments);        channel.queueBind(queueName, exchangeName, routingKey);        //要进行死信队列的声明:        channel.exchangeDeclare("dlx.exchange", "topic", true, false, null);        channel.queueDeclare("dlx.queue", true, false, false, null);        channel.queueBind("dlx.queue", "dlx.exchange", "#");        channel.basicConsume(queueName, true, new MyConsumer(channel));    }}
    
   

package com.zxp.rabbitmqapi.dlx;import com.rabbitmq.client.AMQP;import com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import com.rabbitmq.client.ConnectionFactory;/** * @author笑笑 * @site www.xiaoxiao.com * @company * @create 2020-03-03 10:00 * 生产者 */public class Producer {    public static void main(String[] args) throws Exception {        ConnectionFactory connectionFactory = new ConnectionFactory();        connectionFactory.setHost("192.168.23.129");        connectionFactory.setPort(5672);        connectionFactory.setVirtualHost("/");        Connection connection = connectionFactory.newConnection();        Channel channel = connection.createChannel();        String exchange = "test_dlx_exchange";        String routingKey = "dlx.save";        String msg = "Hello RabbitMQ DLX Message";        for(int i =0; i<1; i ++){            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()                    .deliveryMode(2)                    .contentEncoding("UTF-8")                    .expiration("10000")                    .build();            channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());        }    }}

如果只启动生产者就可以发现它进入了死信。

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