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;
}
}
