Spring RabbitMQ 延迟队列

一、说明

在实际业务场景中可能会用到延时消息发送，例如异步回调失败时的重发机制。 RabbitMQ本身不具有延时消息队列的功能，但是可以通过rabbitmq-delayed-message-exchange来实现（也可以通过TTL(Time To Live)、DLX(Dead Letter Exchanges)特性实现，我们主要讲解通过延迟插件来实现的方法）。利用RabbitMQ的这种特性，应该可以实现很多现实中的业务，我们可以发挥想象。 

二、安装插件

RabbitMQ的安装请参考我的文章“RabbitMQ安装与使用”，这里我们重点讲插件的安装。

首先到http://www.rabbitmq.com/community-plugins.html网页下载适合的“rabbitmq_delayed_message_exchange插件”。下载完成后将它放到RabbitMQ插件安装目录（{rabbitmq-server}/plugins/），然后执行命令rabbitmq-plugins enable rabbitmq_delayed_message_exchange启用插件，执行命令rabbitmq-plugins disable rabbitmq_delayed_message_exchange也可以关闭插件。具体过程可以查看参考文档2。

三、spring集成RabbitMQ

1、maven配置

<dependency>
    <groupId>org.springframework.amqp</groupId>
    <artifactId>spring-amqp</artifactId>
    <version>1.6.6.RELEASE</version>
    <exclusions>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.1.6.RELEASE</version>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.amqp</groupId>
    <artifactId>spring-rabbit</artifactId>
    <version>1.6.6.RELEASE</version>
    <exclusions>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.1.6.RELEASE</version>
        </exclusion>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-messaging</artifactId>
            <version>4.1.6.RELEASE</version>
        </exclusion>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>4.1.6.RELEASE</version>
        </exclusion>
        <exclusion>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.6.RELEASE</version>
        </exclusion>
    </exclusions>
</dependency>

说明：实现延迟队列需要Spring在4.1以上，spring-amqp在1.6以上。

2、xml配置

<?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:tx="http://www.springframework.org/schema/tx"
    xmlns:util="http://www.springframework.org/schema/util" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:rabbit="http://www.springframework.org/schema/rabbit"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                            http://www.springframework.org/schema/context
                            http://www.springframework.org/schema/context/spring-context-3.1.xsd
                            http://www.springframework.org/schema/tx
                            http://www.springframework.org/schema/tx/spring-tx.xsd
                            http://www.springframework.org/schema/aop
                            http://www.springframework.org/schema/aop/spring-aop.xsd
                            http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
                            http://www.springframework.org/schema/rabbit http://www.springframework.org/schema/rabbit/spring-rabbit-1.6.xsd">
    <context:property-placeholder location="classpath:rmq-config.properties" ignore-unresolvable="true"/>

    <bean id="connectionFactory" class="org.springframework.amqp.rabbit.connection.CachingConnectionFactory">
        <property name="host" value="${rabbitmq.host}" />
        <property name="port" value="${rabbitmq.port}" />
        <property name="username" value="${rabbitmq.username}" />
        <property name="password" value="${rabbitmq.password}" />
        <property name="channelCacheSize" value="${rabbitmq.channel.cacheSize}" />
    </bean>

    <bean id="orderConsumer" class="com.xxx.rmq.OrderConsumer"></bean>
    <bean id="messageConverter" class="org.springframework.amqp.support.converter.SimpleMessageConverter" />
    <bean id="jsonMessageConverter" class="org.springframework.amqp.support.converter.Jackson2JsonMessageConverter" />

    <rabbit:admin connection-factory="connectionFactory" />

    <!-- 延迟消息start -->
    <rabbit:topic-exchange name="delay_exchange" delayed="true">
        <rabbit:bindings>
            <rabbit:binding queue="delay_queue" pattern="order.delay.notify" />
        </rabbit:bindings>
    </rabbit:topic-exchange>

    <rabbit:queue name="delay_queue" durable="true" auto-declare="true" auto-delete="false" />

    <rabbit:template id="delayMsgTemplate" connection-factory="connectionFactory" message-converter="jsonMessageConverter" exchange="delay_exchange" />

    <rabbit:listener-container connection-factory="connectionFactory" channel-transacted="false" acknowledge="auto" message-converter="jsonMessageConverter">
        <rabbit:listener queues="delay_queue" ref="orderConsumer" method="delayMsg" />
    </rabbit:listener-container>
    <!-- 延迟消息end -->

</beans>

说明：spring-rabbit-1.6.xsd必须是1.6及以上版本，否则会报“元素 'rabbit:topic-exchange' 中不允许出现属性 'delayed'”错误。具体请查看参考文档3。

四、延迟队列的使用

1、发送消息Producer

import net.sf.json.JSONObject;

import org.apache.commons.lang.StringUtils;
import org.springframework.amqp.AmqpException;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessagePostProcessor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
/**
 *
 * @author Horace
 * @version 创建时间：2016年10月26日 下午6:34:31
 */
@Service
public class MessageProducerServiceImpl implements MessageProducerService{
    @Autowired
    private AmqpTemplate delayMsgTemplate;
    @Override
    public void delayMsg(JSONObject msg,int delay) {
        // TODO Auto-generated method stub
        final int xdelay= delay*1000;
        delayMsgTemplate.convertAndSend("order.delay.notify", (Object) msg,
                new MessagePostProcessor() {

                    @Override
                    public Message postProcessMessage(Message message)
                            throws AmqpException {
                        // TODO Auto-generated method stub
                        message.getMessageProperties().setDelay(xdelay);
                        return message;
                    }
                });
    }
}

2、异步接收消息Consumer

import net.sf.json.JSONObject;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;

/**
 *
 * @author Horace
 * @version 创建时间：2016年10月26日 下午2:48:14
 */
public class OrderConsumer {

    private static Logger logger = LoggerFactory.getLogger(OrderConsumer.class);

    @Autowired
    private MessageProducerService messageProducerService;


    public void delayMsg(Object obj) {
        logger.info("[延时消息]" + obj);
        if (obj != null) {
            JSONObject notifyJson = JSONObject.fromObject(obj);
            String notifyUrl = notifyJson.getString("notifyUrl");
            String notifyContent = notifyJson.getString("notifyContent");
            String result = HttpUtil.postMessage(notifyUrl, notifyContent);
            if (StringUtils.isBlank(result)) { // 通知失败 进入重发机制
                int newNotifyCount = notifyJson.getInt("notifyCount") + 1; //已经通知的次数
                if (newNotifyCount < 5) {
                    notifyJson.put("notifyCount", newNotifyCount);
                    int spacingInterval = getSpacingInterval(newNotifyCount);
                    messageProducerService
                            .delayMsg(notifyJson, spacingInterval);
                } else {
                    logger.info("通知5次都失败，等待后台手工处理！");
                }
            }
        }
    }

    /**
     * 重复通知间隔时间（单位为秒）
     * @param notifyCount 已经通知的次数
     * @return
     */
    private int getSpacingInterval(int notifyCount) {
        // TODO Auto-generated method stub
        int spacingInterval = 0;
        switch (notifyCount) {
        case 1:
            spacingInterval = 10;
            break;
        case 2:
            spacingInterval = 20;
            break;
        case 3:
            spacingInterval = 30;
            break;
        case 4:
            spacingInterval = 60;
            break;
        case 5:
            spacingInterval = 90;
            break;
        default:
            break;
        }
        return spacingInterval;
    }

}