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延迟队列能做什么?###
开发过程中通常会碰到这样的需求:
- 淘宝订单业务:下单后 30min 之内没有付款,就自动取消订单。
- 饿了吗订餐通知:下单成功后 60s 之后给用户发送短信通知。
- 关闭空闲连接:服务器中有很多客户端的连接,空闲一段时间之后需要关闭之。
- 缓存:缓存中的对象,超过了空闲时间,从缓存中移出。
- 任务超时处理:在网络协议滑动窗口请求应答式交互时,处理超时未响应的请求。
- 失败重试机制:业务操作失败后,间隔一定的时间进行失败重试。 这类业务的特点就是:需要延迟工作,需要进行失败重试。一种比较笨的方式是使用一个后台线程,遍历所有对象,挨个检查。这种方法简单好用,但是对象数量过多时,可能存在性能问题,检查间隔时间不好设置,间隔时间过大,影响精确度,过小则存在效率问题,而且做不到按超时的时间顺序处理。
本地延迟队列 DelayQueue
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DelayQueue 是一个无界的 BlockingQueue,用于放置实现了 Delayed 接口的对象,其中的对象只能在其到期时才能从队列中取走。这种队列是有序的,即队头对象的延迟到期时间最长。Delayed 扩展了 Comparable 接口,比较的基准为延时的时间值,Delayed 接口的实现类 getDelay 的返回值应为固定值(final)。DelayQueue 内部是使用 PriorityQueue 实现的。
DelayQueue = BlockingQueue + PriorityQueue + Delayed
DelayQueue 的关键元素 BlockingQueue、PriorityQueue、Delayed。可以这么说,DelayQueue 是一个使用优先队列(PriorityQueue)实现的 BlockingQueue,优先队列的比较基准值是时间。注意:不能将 null 元素放置到这种队列中。
但是我们知道,利用 DelayQueue 实现的是一个单机的、JVM 内存中的延迟队列,并没有集群的支持,而且无法满足在对业务系统泵机的时、消息消费异常的时候做相应的逻辑处理。
基于分布式消息队列 RabbitMQ 实现延迟队列
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RabbitMQ 本身没有直接支持延迟队列功能,但是可以通过以下特性模拟出延迟队列的功能:
1> Per-Queue Message TTL RabbitMQ 可以对消息和队列设置 TTL(过期时间)。
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RabbitMQ 针对队列中的消息过期时间(Time To Live, TTL)有两种方法可以设置。第一种方法是通过队列属性设置,队列中所有消息都有相同的过期时间。第二种方法是对消息进行单独设置,每条消息 TTL 可以不同。如果上述两种方法同时使用,则消息的过期时间以两者之间 TTL 较小的那个数值为准。消息在队列的生存时间一旦超过设置的 TTL 值,就成为 dead message, 消费者将无法再收到该消息。
2> Dead Letter Exchanges 死信消息
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利用 DLX,当消息在一个队列中变成死信后,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:
- 消息被拒绝(basic.reject or basic.nack)并且 requeue=false
- 消息 TTL 过期
- 队列达到最大长度
DLX 也是一下正常的 Exchange 同一般的 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,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 中去,进而被路由到另一个队列,publish 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 RabbitMQ 3.0.0 以前支持的 immediate 参数中的向 publish 确认的功能。
结合以上两个特性,就可以模拟出延迟消息的功能.流程图
源代码
package hbec.app.stock.rabbitmq.utils;
import java.io.IOException;
import java.util.HashMap; import java.util.concurrent.TimeUnit;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import com.google.common.base.Preconditions;
import com.google.common.collect.Maps; import com.rabbitmq.client.AMQP; import com.rabbitmq.client.Channel; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Consumer;/**
* @Description 基于 RabbitMQ 实现的分布式延迟重试队列 * *- *
- delayExchangeName : 交换器名称 *
- delayQueueName : 延迟队列名称 *
- delayRoutingKeyName : 路由器名称 *
- perDelayQueueMessageTTL : 延迟队列中 message 的默认 ttl *
private static Logger LOGGER = LoggerFactory.getLogger(RabbitMQDelayQueue.class);private static final String POSTFIX_TASK = "_task";// direct类型 交换器public static final String EXCHANGE_TYPE_DIRECT = "direct";private Connection connection;//注册消费者private ConsumerRegister consumerRegister;//任务队列配置private String taskExchangeName;private String taskQueueName;private String taskRoutingKeyName;//延迟队列配置private String delayExchangeName;private String delayQueueName;private String delayRoutingKeyName;//延迟队列中的消息ttlprivate long perDelayQueueMessageTTL;public RabbitMQDelayQueue(Connection connection, ConsumerRegister consumerRegister, String delayExchangeName, String delayQueueName, String delayRoutingKeyName, long perDelayQueueMessageTTL) throws IOException { this.connection = connection; this.consumerRegister = consumerRegister; this.delayExchangeName = delayExchangeName; this.delayQueueName = delayQueueName; this.delayRoutingKeyName = delayRoutingKeyName; this.perDelayQueueMessageTTL = perDelayQueueMessageTTL; this.taskExchangeName = delayExchangeName + POSTFIX_TASK; this.taskQueueName = delayQueueName + POSTFIX_TASK; this.taskRoutingKeyName = delayRoutingKeyName + POSTFIX_TASK; init(); registerConsumer();}/** * * @Description 注册消费者 * @author roc roc.fly@qq.com * @date Dec 29, 2016 1:36:25 PM */public interface ConsumerRegister { public Consumer register(Channel channel) throws IOException;}/** * 注册带有ttl的queue和对应的任务队列 * * @throws IOException * @author roc */private void init() throws IOException { Channel channel = connection.createChannel(); channel.exchangeDeclare(taskExchangeName, EXCHANGE_TYPE_DIRECT, true); channel.exchangeDeclare(delayExchangeName, EXCHANGE_TYPE_DIRECT, true); // 任务队列 B HashMapargumentsTask = Maps.newHashMap(); argumentsTask.put("x-dead-letter-exchange", delayExchangeName); argumentsTask.put("x-dead-letter-routing-key", delayRoutingKeyName); channel.queueDeclare(taskQueueName, true, false, false, argumentsTask); channel.queueBind(taskQueueName, taskExchangeName, taskRoutingKeyName); // 延迟队列 A HashMap argumentsDelay = Maps.newHashMap(); argumentsDelay.put("x-dead-letter-exchange", taskExchangeName); argumentsDelay.put("x-dead-letter-routing-key", taskRoutingKeyName); argumentsDelay.put("x-message-ttl", perDelayQueueMessageTTL); channel.queueDeclare(delayQueueName, true, false, false, argumentsDelay); channel.queueBind(delayQueueName, delayExchangeName, delayRoutingKeyName); channel.close();}/** * 注册消费者 * @throws IOException * @author roc */private void registerConsumer() throws IOException { LOGGER.info("register consumer ->{}", this); Channel channel = connection.createChannel(); Consumer consumer = consumerRegister.register(channel); channel.basicConsume(taskQueueName, false, consumer); LOGGER.info("register consumer ->{} success", this);}/** * 消息入队 * * @param body 消息内容 * @param timeout 超时时间 * @param unit 超时时间单位 * @throws IOException * @author roc */public void put(byte[] body, long timeout, TimeUnit unit) throws IOException { Preconditions.checkNotNull(body); Preconditions.checkArgument(timeout >= 0); Preconditions.checkNotNull(unit); LOGGER.info("put element to delay queue ->{}", body.hashCode()); Channel channel = null; try { channel = connection.createChannel(); // deliveryMode=2 标识任务的持久性 long millis = unit.toMillis(timeout); AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder().expiration(String.valueOf(millis)).deliveryMode(2).build(); channel.basicPublish(delayExchangeName, delayRoutingKeyName, properties, body); LOGGER.info("put element to delay queue success"); } finally { if (null != channel) channel.close(); }}public static class Builder { private Connection connection; private ConsumerRegister consumerRegister; private String delayExchangeName; private String delayQueueName; private String delayRoutingKeyName; private long perDelayQueueMessageTTL; public Builder setConnection(Connection connection) { this.connection = connection; return this; } public Builder setDelayExchangeName(String delayExchangeName) { this.delayExchangeName = delayExchangeName; return this; } public Builder setDelayQueueName(String delayQueueName) { this.delayQueueName = delayQueueName; return this; } public Builder setDelayRoutingKeyName(String delayRoutingKeyName) { this.delayRoutingKeyName = delayRoutingKeyName; return this; } public Builder setConsumerRegister(ConsumerRegister consumerRegister) { this.consumerRegister = consumerRegister; return this; } public Builder setPerDelayQueueMessageTTL(long timeout, TimeUnit unit) { this.perDelayQueueMessageTTL = unit.toMillis(timeout);; return this; } public RabbitMQDelayQueue build() throws IOException { Preconditions.checkNotNull(connection); Preconditions.checkNotNull(delayExchangeName); Preconditions.checkNotNull(delayQueueName); Preconditions.checkNotNull(delayRoutingKeyName); Preconditions.checkNotNull(consumerRegister); return new RabbitMQDelayQueue(connection, consumerRegister, delayExchangeName, delayQueueName, delayRoutingKeyName, perDelayQueueMessageTTL); }}
}
测试代码
package hbec.app.stock.rabbitmq.utils;
import hbec.app.stock.rabbitmq.utils.RabbitMQDelayQueue.ConsumerRegister;
import java.io.IOException;
import java.nio.charset.Charset; import java.util.List; import java.util.Map; import java.util.concurrent.TimeUnit;import com.rabbitmq.client.AMQP.BasicProperties;
import com.rabbitmq.client.Address; import com.rabbitmq.client.Channel; import com.rabbitmq.client.Connection; import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Consumer; import com.rabbitmq.client.DefaultConsumer; import com.rabbitmq.client.Envelope;/**
* 测试 demo * */ public class RabbitMQDelayQueueTest {public static void main(String[] args) throws IOException { delayQueue();}public static void delayQueue() throws IOException { ConnectionFactory factory = new ConnectionFactory(); factory.setUsername("guest"); factory.setPassword("guest"); Address address = new Address("10.0.30.67", 56720); Connection connection = factory.newConnection(new Address[] { address }); RabbitMQDelayQueue delayQueue = new RabbitMQDelayQueue.Builder().setConnection(connection).setPerDelayQueueMessageTTL(15, TimeUnit.SECONDS).setDelayExchangeName("delay_exchange_roc").setDelayQueueName("delay_queue_roc").setDelayRoutingKeyName("delay_routing_key_roc").setConsumerRegister(new ConsumerRegister() { @Override public Consumer register(Channel channel) throws IOException { return new DefaultConsumer(channel) { @Override public void handleDelivery(String consumerTag, Envelope envelope, BasicProperties properties, byte[] body) throws IOException { long deliveryTag = envelope.getDeliveryTag(); String exchange = envelope.getExchange(); String routingKey = envelope.getRoutingKey(); // TODO do something String content = new String(body, Charset.forName("utf-8")); System.out.println("receive message --- > " + content); Mapheaders = properties.getHeaders(); if (headers != null) { List
}
码字不容易啊,觉得有用的请我喝咖啡~~