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盘点Java中延时任务的多种实现方式

funnee 人气:0

场景描述

①需要实现一个定时发布系统通告的功能,如何实现? ②支付超时,订单自动取消,如何实现?

实现方式

一、挂起线程

推荐指数:★★☆ 优点: JDK原生(JUC包下)支持,无需引入新的依赖; 缺点: (1)基于内存,应用重启(或宕机)会导致任务丢失 (2)基于内存挂起线程实现延时,不支持集群 (3)代码耦合性大,不易维护 (4)一个任务就要新建一个线程绑定任务的执行,容易造成资源浪费

①配置延迟任务专用线程池

/**
 * 线程池配置
 */
@Configuration
@EnableAsync
@EnableConfigurationProperties(ThreadPoolProperties.class)
public class ThreadPoolConfig {

	//ThreadPoolProperties的配置依据需求和服务器配置自行配置
    @Resource
    private ThreadPoolProperties threadPoolProperties;
    //延迟任务队列容量
    private final static int DELAY_TASK_QUEUE_CAPACITY = 100;

    @Bean
    public ThreadPoolTaskExecutor delayTaskExecutor() {
        log.info("start delayTaskExecutor");
        ThreadPoolTaskExecutor threadPool = new ThreadPoolTaskExecutor();
        //配置核心线程数
        threadPool.setCorePoolSize(threadPoolProperties.getCorePoolSize());
        //配置最大线程数
        threadPool.setMaxPoolSize(threadPoolProperties.getMaxPoolSize());
        //配置队列大小
        threadPool.setQueueCapacity(DELAY_TASK_QUEUE_CAPACITY);
        //线程最大存活时间
        threadPool.setKeepAliveSeconds (threadPoolProperties.getKeepAliveSeconds());
        //配置线程池中的线程的名称前缀
        threadPool.setThreadNamePrefix(threadPoolProperties.getThreadNamePrefix());

        // rejection-policy:当pool已经达到max size的时候执行的策略
        threadPool.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());
        //执行初始化
        threadPool.initialize();
        return threadPool;
    }
}

②创建延时任务

在需要执行的代码块创建延时任务

delayTaskExecutor.execute(() -> {
    try {
        //线程挂起指定时间
        TimeUnit.MINUTES.sleep(time);
        //执行业务逻辑
        doSomething();
    } catch (InterruptedException e) {
        log.error("线程被打断,执行业务逻辑失败");
    }
});

二、ScheduledExecutorService 延迟任务线程池

推荐指数:★★★ 优点: 代码简洁,JDK原生支持 缺点: (1)基于内存,应用重启(或宕机)会导致任务丢失 (2)基于内存存放任务,不支持集群 (3)一个任务就要新建一个线程绑定任务的执行,容易造成资源浪费

class Task implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getId()+":"+Thread.currentThread().getName());
        System.out.println("scheduledExecutorService====>>>延时器");
    }
}
public class ScheduleServiceTest {
    public static void main(String[] args) {
        ScheduledExecutorService scheduledExecutorService=new ScheduledThreadPoolExecutor(10);
        scheduledExecutorService.schedule(new Task(),1, TimeUnit.SECONDS);
        scheduledExecutorService.schedule(new Task(),2, TimeUnit.SECONDS);
        scheduledExecutorService.schedule(new Task(),1, TimeUnit.SECONDS);
    }
}

三、DelayQueue(延时队列)

推荐指数:★★★☆ 优点: (1)JDK原生(JUC包下)支持,无需引入新的依赖; (2)可以用一个线程对整个延时队列按序执行; 缺点: (1)基于内存,应用重启(或宕机)会导致任务丢失 (2)基于内存存放队列,不支持集群 (3)依据compareTo方法排列队列,调用take阻塞式的取出第一个任务(不调用则不取出),比较不灵活,会影响时间的准确性

①新建一个延时任务

public class DelayTask implements Delayed {

    private Integer taskId;

    private long executeTime;

    DelayTask(Integer taskId, long executeTime) {
        this.taskId = taskId;
        this.executeTime = executeTime;
    }

    /**
     * 该任务的延时时长
     * @param unit
     * @return
     */
    @Override
    public long getDelay(TimeUnit unit) {
        return executeTime - System.currentTimeMillis();
    }

    @Override
    public int compareTo(Delayed o) {
        DelayTask t = (DelayTask) o;
        if (this.executeTime - t.executeTime <= 0) {
            return -1;
        } else {
            return 1;
        }
    }

    @Override
    public String toString() {
        return "延时任务{" +
                "任务编号=" + taskId +
                ", 执行时间=" + new Date(executeTime) +
                '}';
    }

    /**
     * 执行具体业务代码
     */
    public void doTask(){
        System.out.println(this+":");
        System.out.println("线程ID-"+Thread.currentThread().getId()+":线程名称-"+Thread.currentThread().getName()+":do something!");
    }
}

②执行延时任务

public class TestDelay {
    public static void main(String[] args) throws InterruptedException {
        // 新建3个任务,并依次设置超时时间为 30s 10s 60s
        DelayTask d1 = new DelayTask(1, System.currentTimeMillis() + 3000L);
        DelayTask d2 = new DelayTask(2, System.currentTimeMillis() + 1000L);
        DelayTask d3 = new DelayTask(3, System.currentTimeMillis() + 6000L);

        DelayQueue<DelayTask> queue = new DelayQueue<>();
        queue.add(d1);
        queue.add(d2);
        queue.add(d3);

        System.out.println("开启延时队列时间:" + new Date()+"\n");

        // 从延时队列中获取元素
        while (!queue.isEmpty()) {
            queue.take().doTask();
        }
        System.out.println("\n任务结束");
    }
}

执行结果:

四、Redis-为key指定超时时长,并监听失效key

推荐指数:★★★☆ 优点: 对于有依赖redis的业务且有延时任务的需求,能够快速对接 缺点: (1)客户端断开后重连会导致所有事件丢失 (2)高并发场景下,存在大量的失效key场景会导出失效时间存在延迟 (3)若有多个监听器监听该key,是会重复消费这个过期事件的,需要特定逻辑判断

① 修改Redis配置文件并重启Redis

notify-keyspace-events Ex

注意: redis配置文件不能有空格,否则会启动报错

②Java中关于Redis的配置类

redisTemplate实例bean需要自定义生成; RedisMessageListenerContainer 是redis-key过期监听需要的监听器容器;

@Configuration
@Slf4j
public class RedisConfiguration {
    /**
     * Redis配置
     * @param factory
     * @return
     */
    @Bean(name = "redisTemplate")
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<Object, Object> template = new RedisTemplate<>();
        RedisSerializer<String> redisSerializer = new StringRedisSerializer();

        template.setConnectionFactory(factory);
        //key序列化方式
        template.setKeySerializer(redisSerializer);
        //value序列化
        template.setValueSerializer(redisSerializer);
        //value hashmap序列化
        template.setHashValueSerializer(redisSerializer);
        //key hashmap序列化
        template.setHashKeySerializer(redisSerializer);

        return template;
    }

    /**
     * 消息监听器容器bean
     * @param connectionFactory
     * @return
     */
    @Bean
    public RedisMessageListenerContainer container(LettuceConnectionFactory connectionFactory) {

        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        return container;
    }
}

③监听器代码

@Slf4j
@Component
public class RedisKeyExpirationListener extends KeyExpirationEventMessageListener {
    private static final String TEST_REDIS_KEY = "testExpired";
    public RedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer,
                                      RedisTemplate redisTemplate) {
        super(listenerContainer);
        /**
         * 设置一个Redis延迟过期key(key名:testExpired,过期时间:30秒)
         */
        redisTemplate.opsForValue().set(TEST_REDIS_KEY, "1", 20, TimeUnit.SECONDS);
        log.info("设置redis-key");
    }

    @Override
    public void onMessage(Message message, byte[] pattern) {
        try {
            String expiredKey = message.toString();
            if (TEST_REDIS_KEY.equals(expiredKey)) {
                //业务处理
                log.info(expiredKey + "过期,触发回调");
            }
        } catch (Exception e) {
            log.error("key 过期通知处理异常,{}", e);
        }

    }
}

测试结果:

五、时间轮

推荐指数:★★★★ 优点: (1)对于大量定时任务,时间轮可以仅用一个工作线程对编排的任务进行顺序运行; (2)自动运行,可以自定义时间轮每轮的tick数,tick间隔,灵活且时间精度可控 缺点: (1)基于内存,应用重启(或宕机)会导致任务丢失 (2)基于内存存放任务,不支持集群

public class WheelTimerTest {

    public static void main(String[] args) {

        //设置每个格子是 100ms, 总共 256 个格子
        HashedWheelTimer hashedWheelTimer = new HashedWheelTimer(100, TimeUnit.MILLISECONDS, 256);

        //加入三个任务,依次设置超时时间是 10s 5s 20s

        System.out.println("加入一个任务,ID = 1, time= " + LocalDateTime.now());
        hashedWheelTimer.newTimeout(timeout -> {
            System.out.println(Thread.currentThread().getName());
            System.out.println("执行一个任务,ID = 1, time= " + LocalDateTime.now());
        }, 10, TimeUnit.SECONDS);

        System.out.println("加入一个任务,ID = 2, time= " + LocalDateTime.now());
        hashedWheelTimer.newTimeout(timeout -> {
            System.out.println(Thread.currentThread().getName());
            System.out.println("执行一个任务,ID = 2, time= " + LocalDateTime.now());
        }, 5, TimeUnit.SECONDS);

        System.out.println("加入一个任务,ID = 3, time= " + LocalDateTime.now());
        hashedWheelTimer.newTimeout(timeout -> {
            System.out.println(Thread.currentThread().getName());
            System.out.println("执行一个任务,ID = 3, time= " + LocalDateTime.now());
        }, 20, TimeUnit.SECONDS);
        System.out.println("加入一个任务,ID = 4, time= " + LocalDateTime.now());
        hashedWheelTimer.newTimeout(timeout -> {
            System.out.println(Thread.currentThread().getName());
            System.out.println("执行一个任务,ID = 4, time= " + LocalDateTime.now());
        }, 20, TimeUnit.SECONDS);

        System.out.println("等待任务执行===========");
    }
}

六、消息队列-延迟队列

针对任务丢失的代价过大,高并发的场景 推荐指数:★★★★ 优点: 支持集群,分布式,高并发场景; 缺点: 引入额外的消息队列,增加项目的部署和维护的复杂度。

场景:为一个委托指定期限,委托到期后,委托关系终止,相关业务权限移交回原拥有者 这里采用的是RabbitMq的死信队列加TTL消息转化为延迟队列的方式(RabbitMq没有延时队列)

①声明一个队列设定其的死信队列

@Configuration
public class MqConfig {
    public static final String GLOBAL_RABBIT_TEMPLATE = "rabbitTemplateGlobal";

    public static final String DLX_EXCHANGE_NAME = "dlxExchange";
    public static final String AUTH_EXCHANGE_NAME = "authExchange";

    public static final String DLX_QUEUE_NAME = "dlxQueue";
    public static final String AUTH_QUEUE_NAME = "authQueue";
    public static final String DLX_AUTH_QUEUE_NAME = "dlxAuthQueue";

    @Bean
    @Qualifier(GLOBAL_RABBIT_TEMPLATE)
    public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) {
        RabbitTemplate rabbitTemplate = new RabbitTemplate(connectionFactory);
        return rabbitTemplate;
    }

    @Bean
    @Qualifier(AUTH_EXCHANGE_NAME)
    public Exchange authExchange() {
        return ExchangeBuilder.directExchange (AUTH_EXCHANGE_NAME).durable (true).build ();
    }

    /**
     * 死信交换机
     * @return
     */
    @Bean
    @Qualifier(DLX_EXCHANGE_NAME)
    public Exchange dlxExchange() {
        return ExchangeBuilder.directExchange (DLX_EXCHANGE_NAME).durable (true).build ();
    }

    /**
     * 记录日志的死信队列
     * @return
     */
    @Bean
    @Qualifier(DLX_QUEUE_NAME)
    public Queue dlxQueue() {
        // Queue(String name, boolean durable, boolean exclusive, boolean autoDelete, Map<String, Object> arguments)
        return QueueBuilder.durable (DLX_QUEUE_NAME).build ();
    }

    /**
     * 委托授权专用队列
     * @return
     */
    @Bean
    @Qualifier(AUTH_QUEUE_NAME)
    public Queue authQueue() {
        return QueueBuilder
                .durable (AUTH_QUEUE_NAME)
                .withArgument("x-dead-letter-exchange", DLX_EXCHANGE_NAME)
                .withArgument("x-dead-letter-routing-key", "dlx_auth")
                .build ();
    }

    /**
     * 委托授权专用死信队列
     * @return
     */
    @Bean
    @Qualifier(DLX_AUTH_QUEUE_NAME)
    public Queue dlxAuthQueue() {
        // Queue(String name, boolean durable, boolean exclusive, boolean autoDelete, Map<String, Object> arguments)
        return QueueBuilder
                .durable (DLX_AUTH_QUEUE_NAME)
                .withArgument("x-dead-letter-exchange", DLX_EXCHANGE_NAME)
                .withArgument("x-dead-letter-routing-key", "dlx_key")
                .build ();
    }

    @Bean
    public Binding bindDlxQueueExchange(@Qualifier(DLX_QUEUE_NAME) Queue dlxQueue, @Qualifier(DLX_EXCHANGE_NAME) Exchange dlxExchange){
        return BindingBuilder.bind (dlxQueue).to (dlxExchange).with ("dlx_key").noargs ();
    }

    /**
     * 委托授权专用死信队列绑定关系
     * @param dlxAuthQueue
     * @param dlxExchange
     * @return
     */
    @Bean
    public Binding bindDlxAuthQueueExchange(@Qualifier(DLX_AUTH_QUEUE_NAME) Queue dlxAuthQueue, @Qualifier(DLX_EXCHANGE_NAME) Exchange dlxExchange){
        return BindingBuilder.bind (dlxAuthQueue).to (dlxExchange).with ("dlx_auth").noargs ();
    }

    /**
     * 委托授权专用队列绑定关系
     * @param authQueue
     * @param authExchange
     * @return
     */
    @Bean
    public Binding bindAuthQueueExchange(@Qualifier(AUTH_QUEUE_NAME) Queue authQueue, @Qualifier(AUTH_EXCHANGE_NAME) Exchange authExchange){
        return BindingBuilder.bind (authQueue).to (authExchange).with ("auth").noargs ();
    }

}

②发送含过期时间的消息

向授权交换机,发送路由为"auth"的消息(指定了业务所需的超时时间) =》发向MqConfig.AUTH_QUEUE_NAME 队列

rabbitTemplate.convertAndSend(MqConfig.AUTH_EXCHANGE_NAME, "auth", "类型:END,信息:{id:1,fromUserId:111,toUserId:222,beginData:20201204,endData:20211104}", message -> {
            /**
             * MessagePostProcessor:消息后置处理
             * 为消息设置属性,然后返回消息,相当于包装消息的类
             */

            //业务逻辑:过期时间=xxxx
            String ttl = "5000";
            //设置消息的过期时间
            message.getMessageProperties ().setExpiration (ttl);
            return message;
        });

③超时后队列MqConfig.AUTH_QUEUE_NAME会将消息转发至其配置的死信路由"dlx_auth",监听该死信队列即可消费定时的消息

 	/**
     * 授权定时处理
     * @param channel
     * @param message
     */
    @RabbitListener(queues = MqConfig.DLX_AUTH_QUEUE_NAME)
    public void dlxAuthQ(Channel channel, Message message) throws IOException {
        System.out.println ("\n死信原因:" + message.getMessageProperties ().getHeaders ().get ("x-first-death-reason"));
        //1.判断消息类型:1.BEGIN 2.END
        try {
            //2.1 类型为授权到期(END)
            //2.1.1 修改报件办理人
            //2.1.2 修改授权状态为0(失效)

            //2.2 类型为授权开启(BEGIN)
            //2.2.1 修改授权状态为1(开启)
            System.out.println (new String(message.getBody (), Charset.forName ("utf8")));
            channel.basicAck (message.getMessageProperties ().getDeliveryTag (),  false);
            System.out.println ("已处理,授权相关信息修改成功");
        } catch (Exception e) {
            //拒签消息
            channel.basicNack (message.getMessageProperties ().getDeliveryTag (), false, false);
            System.out.println ("授权相关信息处理失败, 进入死信队列记录日志");
        }
    }

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