二、RabbitMQ之延时消息（2）

rabbitmq安装延时插件 rabbitmq_delayed_message_exchange

1.到官网https://www.rabbitmq.com/community-plugins.html，下载对应版本的rabbitmq_delayed_message_exchange

2.将插件拷贝到rabbitmq的plugins目录下，我本地使用的docker启动的rabbitmq服务，使用命令 docker cp rabbitmq_delayed_message_exchange-3.8.0.ez 容器ID:/plugins

3.进入容器内部，docker exec -it 5af /bin/bash， 进入plugins目录，查看是否拷贝成功 cd /plugins

4.启用延时插件，执行命令 rabbitmq-plugins enable rabbitmq_delayed_message_exchange

 5.打开web页面的Exchange模块，可以看见多了一种类型（PS:如果没有看见，可以重启一下服务）

 6.测试

import org.springframework.amqp.core.*;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.HashMap;
import java.util.Map;
 
@Configuration
public class MQExchangeConfig {

    public static final String CUSTOM_EXCHANGE_NAME = "custom-Exchange";
   
    public static final String QUEUEA_NAME = "queueA";
    public static final String QUEUEB_NAME = "queueB";
    public static final String ROUTING_KEY_A_NAME = "routingKeyA";
    public static final String ROUTING_KEY_B_NAME = "routingKeyB";


    @Bean
    CustomExchange customExchange() {
        Map<String, Object> args = new HashMap<String, Object>();
        //路由策略，必填项，参考ExchangeTypes
        args.put("x-delayed-type", "direct");
        return new CustomExchange(CUSTOM_EXCHANGE_NAME, "x-delayed-message", true, false, args);
    }

    @Bean
    Queue queueA() {
        return new Queue(QUEUEA_NAME);
    }

    @Bean
    Queue queueB() {
        return new Queue(QUEUEB_NAME);
    }

    @Bean
    Binding bindingAC(Queue queueA, CustomExchange customExchange) {
        return BindingBuilder.bind(queueA).to(customExchange).with(ROUTING_KEY_A_NAME).noargs();
    }

    @Bean
    Binding bindingBC(Queue queueB, CustomExchange customExchange) {
        return BindingBuilder.bind(queueB).to(customExchange).with(ROUTING_KEY_B_NAME).noargs();
    }

    //先初始化队列
    @Bean
    @ConditionalOnBean(Queue.class)
    MQExchangeConsumer mqExchangeConsumer() {
        return new MQExchangeConsumer();
    }
}

//发送消息，注意：延时时间设置：Delay > 0, Delay =< ?ERL_MAX_T (In Erlang a timer can be set up to (2^32)-1 milliseconds in the future).

 rabbitTemplate.convertSendAndReceive(CUSTOM_EXCHANGE_NAME, ROUTING_KEY_A_NAME, msg + "a", message -> {
                    // 本质还是设置header的x-delay=10000,可以参考日志信息
                    message.getMessageProperties().setDelay(10000);
                    return message;
                });
                rabbitTemplate.convertSendAndReceive(CUSTOM_EXCHANGE_NAME, ROUTING_KEY_B_NAME, msg + "b", message -> {
                    message.getMessageProperties().setHeader("x-delay", 20000);
                    return message;
                });

//结果

7.停用延时插件

执行命令：rabbitmq-plugins disable rabbitmq_delayed_message_exchange。

注：停用后延时未分发的消息将会丢失

8.其他

消息分发前是存储在节点下的Mnesia table中，通过计时器调度实现分发，官网写到:这个插件的设计并不适合大量延迟消息的情况（例如100s数千条或数百万条）。因为随着mnesia数据库的增长，延迟消息的延时时间变得难以控制，就很难达到预期的效果