使用Redis实现延时任务(一)

前提

最近在生产环境刚好遇到了延时任务的场景，调研了一下目前主流的方案，分析了一下优劣并且敲定了最终的方案。这篇文章记录了调研的过程，以及初步方案的实现。

候选方案对比

下面是想到的几种实现延时任务的方案，总结了一下相应的优势和劣势。

方案	优势	劣势	选用场景
JDK内置的延迟队列DelayQueue	实现简单	数据内存态，不可靠	一致性相对低的场景
调度框架和MySQL进行短间隔轮询	实现简单，可靠性高	存在明显的性能瓶颈	数据量较少实时性相对低的场景
RabbitMQ的DLX和TTL，一般称为死信队列方案	异步交互可以削峰	延时的时间长度不可控，如果数据需要持久化则性能会降低	-
调度框架和Redis进行短间隔轮询	数据持久化，高性能	实现难度大	常见于支付结果回调方案
时间轮	实时性高	实现难度大，内存消耗大	实时性高的场景

如果应用的数据量不高，实时性要求比较低，选用调度框架和MySQL进行短间隔轮询这个方案是最优的方案。但是笔者遇到的场景数据量相对比较大，实时性并不高，采用扫库的方案一定会对MySQL实例造成比较大的压力。记得很早之前，看过一个PPT叫《盒子科技聚合支付系统演进》，其中里面有一张图片给予笔者一点启发：

里面刚好用到了调度框架和Redis进行短间隔轮询实现延时任务的方案，不过为了分摊应用的压力，图中的方案还做了分片处理。鉴于笔者当前业务紧迫，所以在第一期的方案暂时不考虑分片，只做了一个简化版的实现。

由于PPT中没有任何的代码或者框架贴出，有些需要解决的技术点需要自行思考，下面会重现一次整个方案实现的详细过程。

场景设计

实际的生产场景是笔者负责的某个系统需要对接一个外部的资金方，每一笔资金下单后需要延时30分钟推送对应的附件。这里简化为一个订单信息数据延迟处理的场景，就是每一笔下单记录一条订单消息(暂时叫做OrderMessage)，订单消息需要延迟5到15秒后进行异步处理。

否决的候选方案实现思路

下面介绍一下其它四个不选用的候选方案，结合一些伪代码和流程分析一下实现过程。

JDK内置延迟队列

DelayQueue是一个阻塞队列的实现，它的队列元素必须是Delayed的子类，这里做个简单的例子：

public class DelayQueueMain {

    private static final Logger LOGGER = LoggerFactory.getLogger(DelayQueueMain.class);

    public static void main(String[] args) throws Exception {
        DelayQueue queue = new DelayQueue<>();
        // 默认延迟5秒
        OrderMessage message = new OrderMessage("ORDER_ID_10086");
        queue.add(message);
        // 延迟6秒
        message = new OrderMessage("ORDER_ID_10087", 6);
        queue.add(message);
        // 延迟10秒
        message = new OrderMessage("ORDER_ID_10088", 10);
        queue.add(message);
        ExecutorService executorService = Executors.newSingleThreadExecutor(r -> {
            Thread thread = new Thread(r);
            thread.setName("DelayWorker");
            thread.setDaemon(true);
            return thread;
        });
        LOGGER.info("开始执行调度线程...");
        executorService.execute(() -> {
            while (true) {
                try {
                    OrderMessage task = queue.take();
                    LOGGER.info("延迟处理订单消息,{}", task.getDescription());
                } catch (Exception e) {
                    LOGGER.error(e.getMessage(), e);
                }
            }
        });
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class OrderMessage implements Delayed {

        private static final DateTimeFormatter F = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

        /**
         * 默认延迟5000毫秒
         */
        private static final long DELAY_MS = 1000L * 5;

        /**
         * 订单ID
         */
        private final String orderId;

        /**
         * 创建时间戳
         */
        private final long timestamp;

        /**
         * 过期时间
         */
        private final long expire;

        /**
         * 描述
         */
        private final String description;

        public OrderMessage(String orderId, long expireSeconds) {
            this.orderId = orderId;
            this.timestamp = System.currentTimeMillis();
            this.expire = this.timestamp + expireSeconds * 1000L;
            this.description = String.format("订单[%s]-创建时间为:%s,超时时间为:%s", orderId,
                    LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).format(F),
                    LocalDateTime.ofInstant(Instant.ofEpochMilli(expire), ZoneId.systemDefault()).format(F));
        }

        public OrderMessage(String orderId) {
            this.orderId = orderId;
            this.timestamp = System.currentTimeMillis();
            this.expire = this.timestamp + DELAY_MS;
            this.description = String.format("订单[%s]-创建时间为:%s,超时时间为:%s", orderId,
                    LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).format(F),
                    LocalDateTime.ofInstant(Instant.ofEpochMilli(expire), ZoneId.systemDefault()).format(F));
        }

        public String getOrderId() {
            return orderId;
        }

        public long getTimestamp() {
            return timestamp;
        }

        public long getExpire() {
            return expire;
        }

        public String getDescription() {
            return description;
        }

        @Override
        public long getDelay(TimeUnit unit) {
            return unit.convert(this.expire - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
        }

        @Override
        public int compareTo(Delayed o) {
            return (int) (this.getDelay(TimeUnit.MILLISECONDS) - o.getDelay(TimeUnit.MILLISECONDS));
        }
    }
}

注意一下，OrderMessage实现Delayed接口，关键是需要实现Delayed#getDelay()和Delayed#compareTo()。运行一下main()方法：

10:16:08.240 [main] INFO club.throwable.delay.DelayQueueMain - 开始执行调度线程...
10:16:13.224 [DelayWorker] INFO club.throwable.delay.DelayQueueMain - 延迟处理订单消息,订单[ORDER_ID_10086]-创建时间为:2019-08-20 10:16:08,超时时间为:2019-08-20 10:16:13
10:16:14.237 [DelayWorker] INFO club.throwable.delay.DelayQueueMain - 延迟处理订单消息,订单[ORDER_ID_10087]-创建时间为:2019-08-20 10:16:08,超时时间为:2019-08-20 10:16:14
10:16:18.237 [DelayWorker] INFO club.throwable.delay.DelayQueueMain - 延迟处理订单消息,订单[ORDER_ID_10088]-创建时间为:2019-08-20 10:16:08,超时时间为:2019-08-20 10:16:18

调度框架 + MySQL

使用调度框架对MySQL表进行短间隔轮询是实现难度比较低的方案，通常服务刚上线，表数据不多并且实时性不高的情况下应该首选这个方案。不过要注意以下几点：

• 注意轮询间隔不能太短，否则会对MySQL实例产生影响。
• 注意每次查询的数量，结果集数量太多有可能会导致调度阻塞和占用应用大量内存，从而影响时效性。
• 注意要设计状态值和最大重试次数，这样才能尽量避免大量数据积压和重复查询的问题。
• 最好通过时间列做索引，查询指定时间范围内的数据。

引入Quartz、MySQL的Java驱动包和spring-boot-starter-jdbc（这里只是为了方便用相对轻量级的框架实现，生产中可以按场景按需选择其他更合理的框架）：

    mysql
    mysql-connector-java
    5.1.48
    test


    org.springframework.boot
    spring-boot-starter-jdbc
    2.1.7.RELEASE
    test


    org.quartz-scheduler
    quartz
    2.3.1
    test

假设表设计如下：

CREATE DATABASE `delayTask` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci;

USE `delayTask`;

CREATE TABLE `t_order_message`
(
    id           BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
    order_id     VARCHAR(50) NOT NULL COMMENT '订单ID',
    create_time  DATETIME    NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建日期时间',
    edit_time    DATETIME    NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '修改日期时间',
    retry_times  TINYINT     NOT NULL DEFAULT 0 COMMENT '重试次数',
    order_status TINYINT     NOT NULL DEFAULT 0 COMMENT '订单状态',
    INDEX idx_order_id (order_id),
    INDEX idx_create_time (create_time)
) COMMENT '订单信息表';

# 写入两条测试数据
INSERT INTO t_order_message(order_id) VALUES ('10086'),('10087');

编写代码：

// 常量
public class OrderConstants {

    public static final int MAX_RETRY_TIMES = 5;

    public static final int PENDING = 0;

    public static final int SUCCESS = 1;

    public static final int FAIL = -1;

    public static final int LIMIT = 10;
}

// 实体
@Builder
@Data
public class OrderMessage {

    private Long id;
    private String orderId;
    private LocalDateTime createTime;
    private LocalDateTime editTime;
    private Integer retryTimes;
    private Integer orderStatus;
}

// DAO
@RequiredArgsConstructor
public class OrderMessageDao {

    private final JdbcTemplate jdbcTemplate;

    private static final ResultSetExtractor> M = r -> {
        List list = Lists.newArrayList();
        while (r.next()) {
            list.add(OrderMessage.builder()
                    .id(r.getLong("id"))
                    .orderId(r.getString("order_id"))
                    .createTime(r.getTimestamp("create_time").toLocalDateTime())
                    .editTime(r.getTimestamp("edit_time").toLocalDateTime())
                    .retryTimes(r.getInt("retry_times"))
                    .orderStatus(r.getInt("order_status"))
                    .build());
        }
        return list;
    };

    public List selectPendingRecords(LocalDateTime start,
                                                   LocalDateTime end,
                                                   List statusList,
                                                   int maxRetryTimes,
                                                   int limit) {
        StringJoiner joiner = new StringJoiner(",");
        statusList.forEach(s -> joiner.add(String.valueOf(s)));
        return jdbcTemplate.query("SELECT * FROM t_order_message WHERE create_time >= ? AND create_time <= ? " +
                        "AND order_status IN (?) AND retry_times < ? LIMIT ?",
                p -> {
                    p.setTimestamp(1, Timestamp.valueOf(start));
                    p.setTimestamp(2, Timestamp.valueOf(end));
                    p.setString(3, joiner.toString());
                    p.setInt(4, maxRetryTimes);
                    p.setInt(5, limit);
                }, M);
    }

    public int updateOrderStatus(Long id, int status) {
        return jdbcTemplate.update("UPDATE t_order_message SET order_status = ?,edit_time = ? WHERE id =?",
                p -> {
                    p.setInt(1, status);
                    p.setTimestamp(2, Timestamp.valueOf(LocalDateTime.now()));
                    p.setLong(3, id);
                });
    }
}

// Service
@RequiredArgsConstructor
public class OrderMessageService {

    private static final Logger LOGGER = LoggerFactory.getLogger(OrderMessageService.class);

    private final OrderMessageDao orderMessageDao;

    private static final List STATUS = Lists.newArrayList();

    static {
        STATUS.add(OrderConstants.PENDING);
        STATUS.add(OrderConstants.FAIL);
    }

    public void executeDelayJob() {
        LOGGER.info("订单处理定时任务开始执行......");
        LocalDateTime end = LocalDateTime.now();
        // 一天前
        LocalDateTime start = end.minusDays(1);
        List list = orderMessageDao.selectPendingRecords(start, end, STATUS, OrderConstants.MAX_RETRY_TIMES, OrderConstants.LIMIT);
        if (!list.isEmpty()) {
            for (OrderMessage m : list) {
                LOGGER.info("处理订单[{}],状态由{}更新为{}", m.getOrderId(), m.getOrderStatus(), OrderConstants.SUCCESS);
                // 这里其实可以优化为批量更新
                orderMessageDao.updateOrderStatus(m.getId(), OrderConstants.SUCCESS);
            }
        }
        LOGGER.info("订单处理定时任务开始完毕......");
    }
}

// Job
@DisallowConcurrentExecution
public class OrderMessageDelayJob implements Job {

    @Override
    public void execute(JobExecutionContext jobExecutionContext) throws JobExecutionException {
        OrderMessageService service = (OrderMessageService) jobExecutionContext.getMergedJobDataMap().get("orderMessageService");
        service.executeDelayJob();
    }

    public static void main(String[] args) throws Exception {
        HikariConfig config = new HikariConfig();
        config.setJdbcUrl("jdbc:mysql://localhost:3306/delayTask?useSSL=false&characterEncoding=utf8");
        config.setDriverClassName(Driver.class.getName());
        config.setUsername("root");
        config.setPassword("root");
        HikariDataSource dataSource = new HikariDataSource(config);
        OrderMessageDao orderMessageDao = new OrderMessageDao(new JdbcTemplate(dataSource));
        OrderMessageService service = new OrderMessageService(orderMessageDao);
        // 内存模式的调度器
        StdSchedulerFactory factory = new StdSchedulerFactory();
        Scheduler scheduler = factory.getScheduler();
        // 这里没有用到IOC容器,直接用Quartz数据集合传递服务引用
        JobDataMap jobDataMap = new JobDataMap();
        jobDataMap.put("orderMessageService", service);
        // 新建Job
        JobDetail job = JobBuilder.newJob(OrderMessageDelayJob.class)
                .withIdentity("orderMessageDelayJob", "delayJob")
                .usingJobData(jobDataMap)
                .build();
        // 新建触发器,10秒执行一次
        Trigger trigger = TriggerBuilder.newTrigger()
                .withIdentity("orderMessageDelayTrigger", "delayJob")
                .withSchedule(SimpleScheduleBuilder.simpleSchedule().withIntervalInSeconds(10).repeatForever())
                .build();
        scheduler.scheduleJob(job, trigger);
        // 启动调度器
        scheduler.start();
        Thread.sleep(Integer.MAX_VALUE);
    }
}

这个例子里面用了create_time做轮询，实际上可以添加一个调度时间schedule_time列做轮询，这样子才能更容易定制空闲时和忙碌时候的调度策略。上面的示例的运行效果如下：

11:58:27.202 [main] INFO org.quartz.core.QuartzScheduler - Scheduler meta-data: Quartz Scheduler (v2.3.1) 'DefaultQuartzScheduler' with instanceId 'NON_CLUSTERED'
  Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.
  NOT STARTED.
  Currently in standby mode.
  Number of jobs executed: 0
  Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 10 threads.
  Using job-store 'org.quartz.simpl.RAMJobStore' - which does not support persistence. and is not clustered.

11:58:27.202 [main] INFO org.quartz.impl.StdSchedulerFactory - Quartz scheduler 'DefaultQuartzScheduler' initialized from default resource file in Quartz package: 'quartz.properties'
11:58:27.202 [main] INFO org.quartz.impl.StdSchedulerFactory - Quartz scheduler version: 2.3.1
11:58:27.209 [main] INFO org.quartz.core.QuartzScheduler - Scheduler DefaultQuartzScheduler_$_NON_CLUSTERED started.
11:58:27.212 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.core.QuartzSchedulerThread - batch acquisition of 1 triggers
11:58:27.217 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.simpl.PropertySettingJobFactory - Producing instance of Job 'delayJob.orderMessageDelayJob', class=club.throwable.jdbc.OrderMessageDelayJob
11:58:27.219 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@10eb8c53
11:58:27.220 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.core.QuartzSchedulerThread - batch acquisition of 0 triggers
11:58:27.221 [DefaultQuartzScheduler_Worker-1] DEBUG org.quartz.core.JobRunShell - Calling execute on job delayJob.orderMessageDelayJob
11:58:34.440 [DefaultQuartzScheduler_Worker-1] INFO club.throwable.jdbc.OrderMessageService - 订单处理定时任务开始执行......
11:58:34.451 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@3d27ece4
11:58:34.459 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@64e808af
11:58:34.470 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@79c8c2b7
11:58:34.477 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@19a62369
11:58:34.485 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - Added connection com.mysql.jdbc.JDBC4Connection@1673d017
11:58:34.485 [HikariPool-1 connection adder] DEBUG com.zaxxer.hikari.pool.HikariPool - HikariPool-1 - After adding stats (total=10, active=0, idle=10, waiting=0)
11:58:34.559 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL query
11:58:34.565 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [SELECT * FROM t_order_message WHERE create_time >= ? AND create_time <= ? AND order_status IN (?) AND retry_times < ? LIMIT ?]
11:58:34.645 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource
11:58:35.210 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - SQLWarning ignored: SQL state '22007', error code '1292', message [Truncated incorrect DOUBLE value: '0,-1']
11:58:35.335 [DefaultQuartzScheduler_Worker-1] INFO club.throwable.jdbc.OrderMessageService - 处理订单[10086],状态由0更新为1
11:58:35.342 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL update
11:58:35.346 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [UPDATE t_order_message SET order_status = ?,edit_time = ? WHERE id =?]
11:58:35.347 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource
11:58:35.354 [DefaultQuartzScheduler_Worker-1] INFO club.throwable.jdbc.OrderMessageService - 处理订单[10087],状态由0更新为1
11:58:35.355 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL update
11:58:35.355 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [UPDATE t_order_message SET order_status = ?,edit_time = ? WHERE id =?]
11:58:35.355 [DefaultQuartzScheduler_Worker-1] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource
11:58:35.361 [DefaultQuartzScheduler_Worker-1] INFO club.throwable.jdbc.OrderMessageService - 订单处理定时任务开始完毕......
11:58:35.363 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.core.QuartzSchedulerThread - batch acquisition of 1 triggers
11:58:37.206 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.simpl.PropertySettingJobFactory - Producing instance of Job 'delayJob.orderMessageDelayJob', class=club.throwable.jdbc.OrderMessageDelayJob
11:58:37.206 [DefaultQuartzScheduler_QuartzSchedulerThread] DEBUG org.quartz.core.QuartzSchedulerThread - batch acquisition of 0 triggers

RabbitMQ死信队列

使用RabbitMQ死信队列依赖于RabbitMQ的两个特性：TTL和DLX。

• TTL：Time To Live，消息存活时间，包括两个维度：队列消息存活时间和消息本身的存活时间。
• DLX：Dead Letter Exchange，死信交换器。

画个图描述一下这两个特性：

下面为了简单起见，TTL使用了针对队列的维度。引入RabbitMQ的Java驱动：

    com.rabbitmq
    amqp-client
    5.7.3
    test

代码如下：

public class DlxMain {

    private static final DateTimeFormatter F = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    private static final Logger LOGGER = LoggerFactory.getLogger(DlxMain.class);

    public static void main(String[] args) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        Connection connection = factory.newConnection();
        Channel producerChannel = connection.createChannel();
        Channel consumerChannel = connection.createChannel();
        // dlx交换器名称为dlx.exchange,类型是direct,绑定键为dlx.key,队列名为dlx.queue
        producerChannel.exchangeDeclare("dlx.exchange", "direct");
        producerChannel.queueDeclare("dlx.queue", false, false, false, null);
        producerChannel.queueBind("dlx.queue", "dlx.exchange", "dlx.key");
        Map queueArgs = new HashMap<>();
        // 设置队列消息过期时间,5秒
        queueArgs.put("x-message-ttl", 5000);
        // 指定DLX相关参数
        queueArgs.put("x-dead-letter-exchange", "dlx.exchange");
        queueArgs.put("x-dead-letter-routing-key", "dlx.key");
        // 声明业务队列
        producerChannel.queueDeclare("business.queue", false, false, false, queueArgs);
        ExecutorService executorService = Executors.newSingleThreadExecutor(r -> {
            Thread thread = new Thread(r);
            thread.setDaemon(true);
            thread.setName("DlxConsumer");
            return thread;
        });
        // 启动消费者
        executorService.execute(() -> {
            try {
                consumerChannel.basicConsume("dlx.queue", true, new DlxConsumer(consumerChannel));
            } catch (IOException e) {
                LOGGER.error(e.getMessage(), e);
            }
        });
        OrderMessage message = new OrderMessage("10086");
        producerChannel.basicPublish("", "business.queue", MessageProperties.TEXT_PLAIN,
                message.getDescription().getBytes(StandardCharsets.UTF_8));
        LOGGER.info("发送消息成功,订单ID:{}", message.getOrderId());

        message = new OrderMessage("10087");
        producerChannel.basicPublish("", "business.queue", MessageProperties.TEXT_PLAIN,
                message.getDescription().getBytes(StandardCharsets.UTF_8));
        LOGGER.info("发送消息成功,订单ID:{}", message.getOrderId());

        message = new OrderMessage("10088");
        producerChannel.basicPublish("", "business.queue", MessageProperties.TEXT_PLAIN,
                message.getDescription().getBytes(StandardCharsets.UTF_8));
        LOGGER.info("发送消息成功,订单ID:{}", message.getOrderId());

        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DlxConsumer extends DefaultConsumer {

        DlxConsumer(Channel channel) {
            super(channel);
        }

        @Override
        public void handleDelivery(String consumerTag,
                                   Envelope envelope,
                                   AMQP.BasicProperties properties,
                                   byte[] body) throws IOException {
            LOGGER.info("处理消息成功:{}", new String(body, StandardCharsets.UTF_8));
        }
    }

    private static class OrderMessage {

        private final String orderId;
        private final long timestamp;
        private final String description;

        OrderMessage(String orderId) {
            this.orderId = orderId;
            this.timestamp = System.currentTimeMillis();
            this.description = String.format("订单[%s],订单创建时间为:%s", orderId,
                    LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).format(F));
        }

        public String getOrderId() {
            return orderId;
        }

        public long getTimestamp() {
            return timestamp;
        }

        public String getDescription() {
            return description;
        }
    }
}

运行main()方法结果如下：

16:35:58.638 [main] INFO club.throwable.dlx.DlxMain - 发送消息成功,订单ID:10086
16:35:58.641 [main] INFO club.throwable.dlx.DlxMain - 发送消息成功,订单ID:10087
16:35:58.641 [main] INFO club.throwable.dlx.DlxMain - 发送消息成功,订单ID:10088
16:36:03.646 [pool-1-thread-4] INFO club.throwable.dlx.DlxMain - 处理消息成功:订单[10086],订单创建时间为:2019-08-20 16:35:58
16:36:03.670 [pool-1-thread-5] INFO club.throwable.dlx.DlxMain - 处理消息成功:订单[10087],订单创建时间为:2019-08-20 16:35:58
16:36:03.670 [pool-1-thread-6] INFO club.throwable.dlx.DlxMain - 处理消息成功:订单[10088],订单创建时间为:2019-08-20 16:35:58

时间轮

时间轮TimingWheel是一种高效、低延迟的调度数据结构，底层采用数组实现存储任务列表的环形队列，示意图如下：

这里暂时不对时间轮和其实现作分析，只简单举例说明怎么使用时间轮实现延时任务。这里使用Netty提供的HashedWheelTimer，引入依赖：

    io.netty
    netty-common
    4.1.39.Final

代码如下：

public class HashedWheelTimerMain {

    private static final DateTimeFormatter F = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");

    public static void main(String[] args) throws Exception {
        AtomicInteger counter = new AtomicInteger();
        ThreadFactory factory = r -> {
            Thread thread = new Thread(r);
            thread.setDaemon(true);
            thread.setName("HashedWheelTimerWorker-" + counter.getAndIncrement());
            return thread;
        };
        // tickDuration - 每tick一次的时间间隔, 每tick一次就会到达下一个槽位
        // unit - tickDuration的时间单位
        // ticksPerWhee - 时间轮中的槽位数
        Timer timer = new HashedWheelTimer(factory, 1, TimeUnit.SECONDS, 60);
        TimerTask timerTask = new DefaultTimerTask("10086");
        timer.newTimeout(timerTask, 5, TimeUnit.SECONDS);
        timerTask = new DefaultTimerTask("10087");
        timer.newTimeout(timerTask, 10, TimeUnit.SECONDS);
        timerTask = new DefaultTimerTask("10088");
        timer.newTimeout(timerTask, 15, TimeUnit.SECONDS);
        Thread.sleep(Integer.MAX_VALUE);
    }

    private static class DefaultTimerTask implements TimerTask {

        private final String orderId;
        private final long timestamp;

        public DefaultTimerTask(String orderId) {
            this.orderId = orderId;
            this.timestamp = System.currentTimeMillis();
        }

        @Override
        public void run(Timeout timeout) throws Exception {
            System.out.println(String.format("任务执行时间:%s,订单创建时间:%s,订单ID:%s",
                    LocalDateTime.now().format(F), LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).format(F), orderId));
        }
    }
}

运行结果：

任务执行时间:2019-08-20 17:19:49.310,订单创建时间:2019-08-20 17:19:43.294,订单ID:10086
任务执行时间:2019-08-20 17:19:54.297,订单创建时间:2019-08-20 17:19:43.301,订单ID:10087
任务执行时间:2019-08-20 17:19:59.297,订单创建时间:2019-08-20 17:19:43.301,订单ID:10088

一般来说，任务执行的时候应该使用另外的业务线程池，以免阻塞时间轮本身的运动。

选用的方案实现过程

最终选用了基于Redis的有序集合Sorted Set和Quartz短轮询进行实现。具体方案是：

1. 订单创建的时候，订单ID和当前时间戳分别作为Sorted Set的member和score添加到订单队列Sorted Set中。
2. 订单创建的时候，订单ID和推送内容JSON字符串分别作为field和value添加到订单队列内容Hash中。
3. 第1步和第2步操作的时候用Lua脚本保证原子性。
4. 使用一个异步线程通过Sorted Set的命令ZREVRANGEBYSCORE弹出指定数量的订单ID对应的订单队列内容Hash中的订单推送内容数据进行处理。

对于第4点处理有两种方案：

• 方案一：弹出订单内容数据的同时进行数据删除，也就是ZREVRANGEBYSCORE、ZREM和HDEL命令要在同一个Lua脚本中执行，这样的话Lua脚本的编写难度大，并且由于弹出数据已经在Redis中删除，如果数据处理失败则可能需要从数据库重新查询补偿。
• 方案二：弹出订单内容数据之后，在数据处理完成的时候再主动删除订单队列Sorted Set和订单队列内容Hash中对应的数据，这样的话需要控制并发，有重复执行的可能性。

最终暂时选用了方案一，也就是从Sorted Set弹出订单ID并且从Hash中获取完推送数据之后马上删除这两个集合中对应的数据。方案的流程图大概是这样：

这里先详细说明一下用到的Redis命令。

Sorted Set相关命令

• ZADD命令 - 将一个或多个成员元素及其分数值加入到有序集当中。

ZADD KEY SCORE1 VALUE1.. SCOREN VALUEN

---

• ZREVRANGEBYSCORE命令 - 返回有序集中指定分数区间内的所有的成员。有序集成员按分数值递减(从大到小)的次序排列。

ZREVRANGEBYSCORE key max min [WITHSCORES] [LIMIT offset count]

• max：分数区间 - 最大分数。
• min：分数区间 - 最小分数。
• WITHSCORES：可选参数，是否返回分数值，指定则会返回得分值。
• LIMIT：可选参数，offset和count原理和MySQL的LIMIT offset,size一致，如果不指定此参数则返回整个集合的数据。

---

• ZREM命令 - 用于移除有序集中的一个或多个成员，不存在的成员将被忽略。

ZREM key member [member ...]

Hash相关命令

• HMSET命令 - 同时将多个field-value(字段-值)对设置到哈希表中。

HMSET KEY_NAME FIELD1 VALUE1 ...FIELDN VALUEN

---

• HDEL命令 - 删除哈希表key中的一个或多个指定字段，不存在的字段将被忽略。

HDEL KEY_NAME FIELD1.. FIELDN

Lua相关

• 加载Lua脚本并且返回脚本的SHA-1字符串：SCRIPT LOAD script。
• 执行已经加载的Lua脚本：EVALSHA sha1 numkeys key [key ...] arg [arg ...]。
• unpack函数可以把table类型的参数转化为可变参数，不过需要注意的是unpack函数必须使用在非变量定义的函数调用的最后一个参数，否则会失效，详细见Stackoverflow的提问table.unpack() only returns the first element。

PS：如果不熟悉Lua语言，建议系统学习一下，因为想用好Redis，一定离不开Lua。

引入依赖：

    
        
            org.springframework.boot
            spring-boot-dependencies
            2.1.7.RELEASE
            pom
            import
        
    



    
        org.quartz-scheduler
        quartz
        2.3.1
    
    
        redis.clients
        jedis
        3.1.0
    
    
        org.springframework.boot
        spring-boot-starter-web
    
    
        org.springframework.boot
        spring-boot-starter-jdbc
        
    
        org.springframework
        spring-context-support
        5.1.9.RELEASE
     
    
        org.projectlombok
        lombok
        1.18.8
        provided
    
    
        com.alibaba
        fastjson
        1.2.59
           

编写Lua脚本/lua/enqueue.lua和/lua/dequeue.lua：

-- /lua/enqueue.lua
local zset_key = KEYS[1]
local hash_key = KEYS[2]
local zset_value = ARGV[1]
local zset_score = ARGV[2]
local hash_field = ARGV[3]
local hash_value = ARGV[4]
redis.call('ZADD', zset_key, zset_score, zset_value)
redis.call('HSET', hash_key, hash_field, hash_value)
return nil

-- /lua/dequeue.lua
-- 参考jesque的部分Lua脚本实现
local zset_key = KEYS[1]
local hash_key = KEYS[2]
local min_score = ARGV[1]
local max_score = ARGV[2]
local offset = ARGV[3]
local limit = ARGV[4]
-- TYPE命令的返回结果是{'ok':'zset'}这样子,这里利用next做一轮迭代
local status, type = next(redis.call('TYPE', zset_key))
if status ~= nil and status == 'ok' then
    if type == 'zset' then
        local list = redis.call('ZREVRANGEBYSCORE', zset_key, max_score, min_score, 'LIMIT', offset, limit)
        if list ~= nil and #list > 0 then
            -- unpack函数能把table转化为可变参数
            redis.call('ZREM', zset_key, unpack(list))
            local result = redis.call('HMGET', hash_key, unpack(list))
            redis.call('HDEL', hash_key, unpack(list))
            return result
        end
    end
end
return nil

编写核心API代码：

// Jedis提供者
@Component
public class JedisProvider implements InitializingBean {

    private JedisPool jedisPool;

    @Override
    public void afterPropertiesSet() throws Exception {
        jedisPool = new JedisPool();
    }

    public Jedis provide(){
        return jedisPool.getResource();
    }
}

// OrderMessage
@Data
public class OrderMessage {

    private String orderId;
    private BigDecimal amount;
    private Long userId;
}

// 延迟队列接口
public interface OrderDelayQueue {

    void enqueue(OrderMessage message);

    List dequeue(String min, String max, String offset, String limit);

    List dequeue();

    String enqueueSha();

    String dequeueSha();
}

// 延迟队列实现类
@RequiredArgsConstructor
@Component
public class RedisOrderDelayQueue implements OrderDelayQueue, InitializingBean {

    private static final String MIN_SCORE = "0";
    private static final String OFFSET = "0";
    private static final String LIMIT = "10";
    private static final String ORDER_QUEUE = "ORDER_QUEUE";
    private static final String ORDER_DETAIL_QUEUE = "ORDER_DETAIL_QUEUE";
    private static final String ENQUEUE_LUA_SCRIPT_LOCATION = "/lua/enqueue.lua";
    private static final String DEQUEUE_LUA_SCRIPT_LOCATION = "/lua/dequeue.lua";
    private static final AtomicReference ENQUEUE_LUA_SHA = new AtomicReference<>();
    private static final AtomicReference DEQUEUE_LUA_SHA = new AtomicReference<>();
    private static final List KEYS = Lists.newArrayList();

    private final JedisProvider jedisProvider;

    static {
        KEYS.add(ORDER_QUEUE);
        KEYS.add(ORDER_DETAIL_QUEUE);
    }

    @Override
    public void enqueue(OrderMessage message) {
        List args = Lists.newArrayList();
        args.add(message.getOrderId());
        args.add(String.valueOf(System.currentTimeMillis()));
        args.add(message.getOrderId());
        args.add(JSON.toJSONString(message));
        try (Jedis jedis = jedisProvider.provide()) {
            jedis.evalsha(ENQUEUE_LUA_SHA.get(), KEYS, args);
        }
    }

    @Override
    public List dequeue() {
        // 30分钟之前
        String maxScore = String.valueOf(System.currentTimeMillis() - 30 * 60 * 1000);
        return dequeue(MIN_SCORE, maxScore, OFFSET, LIMIT);
    }

    @SuppressWarnings("unchecked")
    @Override
    public List dequeue(String min, String max, String offset, String limit) {
        List args = new ArrayList<>();
        args.add(max);
        args.add(min);
        args.add(offset);
        args.add(limit);
        List result = Lists.newArrayList();
        try (Jedis jedis = jedisProvider.provide()) {
            List eval = (List) jedis.evalsha(DEQUEUE_LUA_SHA.get(), KEYS, args);
            if (null != eval) {
                for (String e : eval) {
                    result.add(JSON.parseObject(e, OrderMessage.class));
                }
            }
        }
        return result;
    }

    @Override
    public String enqueueSha() {
        return ENQUEUE_LUA_SHA.get();
    }

    @Override
    public String dequeueSha() {
        return DEQUEUE_LUA_SHA.get();
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // 加载Lua脚本
        loadLuaScript();
    }

    private void loadLuaScript() throws Exception {
        try (Jedis jedis = jedisProvider.provide()) {
            ClassPathResource resource = new ClassPathResource(ENQUEUE_LUA_SCRIPT_LOCATION);
            String luaContent = StreamUtils.copyToString(resource.getInputStream(), StandardCharsets.UTF_8);
            String sha = jedis.scriptLoad(luaContent);
            ENQUEUE_LUA_SHA.compareAndSet(null, sha);
            resource = new ClassPathResource(DEQUEUE_LUA_SCRIPT_LOCATION);
            luaContent = StreamUtils.copyToString(resource.getInputStream(), StandardCharsets.UTF_8);
            sha = jedis.scriptLoad(luaContent);
            DEQUEUE_LUA_SHA.compareAndSet(null, sha);
        }
    }

    public static void main(String[] as) throws Exception {
        DateTimeFormatter f = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
        JedisProvider jedisProvider = new JedisProvider();
        jedisProvider.afterPropertiesSet();
        RedisOrderDelayQueue queue = new RedisOrderDelayQueue(jedisProvider);
        queue.afterPropertiesSet();
        // 写入测试数据
        OrderMessage message = new OrderMessage();
        message.setAmount(BigDecimal.valueOf(10086));
        message.setOrderId("ORDER_ID_10086");
        message.setUserId(10086L);
        message.setTimestamp(LocalDateTime.now().format(f));
        List args = Lists.newArrayList();
        args.add(message.getOrderId());
        // 测试需要,score设置为30分钟之前
        args.add(String.valueOf(System.currentTimeMillis() - 30 * 60 * 1000));
        args.add(message.getOrderId());
        args.add(JSON.toJSONString(message));
        try (Jedis jedis = jedisProvider.provide()) {
            jedis.evalsha(ENQUEUE_LUA_SHA.get(), KEYS, args);
        }
        List dequeue = queue.dequeue();
        System.out.println(dequeue);
    }
}

这里先执行一次main()方法验证一下延迟队列是否生效：

[OrderMessage(orderId=ORDER_ID_10086, amount=10086, userId=10086, timestamp=2019-08-21 08:32:22.885)]

确定延迟队列的代码没有问题，接着编写一个Quartz的Job类型的消费者OrderMessageConsumer：

@DisallowConcurrentExecution
@Component
public class OrderMessageConsumer implements Job {

    private static final AtomicInteger COUNTER = new AtomicInteger();
    private static final ExecutorService BUSINESS_WORKER_POOL = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors(), r -> {
        Thread thread = new Thread(r);
        thread.setDaemon(true);
        thread.setName("OrderMessageConsumerWorker-" + COUNTER.getAndIncrement());
        return thread;
    });
    private static final Logger LOGGER = LoggerFactory.getLogger(OrderMessageConsumer.class);

    @Autowired
    private OrderDelayQueue orderDelayQueue;

    @Override
    public void execute(JobExecutionContext jobExecutionContext) throws JobExecutionException {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        LOGGER.info("订单消息处理定时任务开始执行......");
        List messages = orderDelayQueue.dequeue();
        if (!messages.isEmpty()) {
            // 简单的列表等分放到线程池中执行
            List> partition = Lists.partition(messages, 2);
            int size = partition.size();
            final CountDownLatch latch = new CountDownLatch(size);
            for (List p : partition) {
                BUSINESS_WORKER_POOL.execute(new ConsumeTask(p, latch));
            }
            try {
                latch.await();
            } catch (InterruptedException ignore) {
                //ignore
            }
        }
        stopWatch.stop();
        LOGGER.info("订单消息处理定时任务执行完毕,耗时:{} ms......", stopWatch.getTotalTimeMillis());
    }

    @RequiredArgsConstructor
    private static class ConsumeTask implements Runnable {

        private final List messages;
        private final CountDownLatch latch;

        @Override
        public void run() {
            try {
                // 实际上这里应该单条捕获异常
                for (OrderMessage message : messages) {
                    LOGGER.info("处理订单信息,内容:{}", message);
                }
            } finally {
                latch.countDown();
            }
        }
    }
}      

上面的消费者设计的时候需要有以下考量：

• 使用@DisallowConcurrentExecution注解不允许Job并发执行，其实多个Job并发执行意义不大，因为我们采用的是短间隔的轮询，而Redis是单线程处理命令，在客户端做多线程其实效果不佳。
• 线程池BUSINESS_WORKER_POOL的线程容量或者队列应该综合LIMIT值、等分订单信息列表中使用的size值以及ConsumeTask里面具体的执行时间进行考虑，这里只是为了方便使用了固定容量的线程池。
• ConsumeTask中应该对每一条订单信息的处理单独捕获异常和吞并异常，或者把处理单个订单信息的逻辑封装成一个不抛出异常的方法。

其他Quartz相关的代码：

// Quartz配置类
@Configuration
public class QuartzAutoConfiguration {

    @Bean
    public SchedulerFactoryBean schedulerFactoryBean(QuartzAutowiredJobFactory quartzAutowiredJobFactory) {
        SchedulerFactoryBean factory = new SchedulerFactoryBean();
        factory.setAutoStartup(true);
        factory.setJobFactory(quartzAutowiredJobFactory);
        return factory;
    }

    @Bean
    public QuartzAutowiredJobFactory quartzAutowiredJobFactory() {
        return new QuartzAutowiredJobFactory();
    }

    public static class QuartzAutowiredJobFactory extends AdaptableJobFactory implements BeanFactoryAware {

        private AutowireCapableBeanFactory autowireCapableBeanFactory;

        @Override
        public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
            this.autowireCapableBeanFactory = (AutowireCapableBeanFactory) beanFactory;
        }

        @Override
        protected Object createJobInstance(TriggerFiredBundle bundle) throws Exception {
            Object jobInstance = super.createJobInstance(bundle);
            // 这里利用AutowireCapableBeanFactory从新建的Job实例做一次自动装配,得到一个原型(prototype)的JobBean实例
            autowireCapableBeanFactory.autowireBean(jobInstance);
            return jobInstance;
        }
    }
}

这里暂时使用了内存态的RAMJobStore去存放任务和触发器的相关信息，如果在生产环境最好替换成基于MySQL也就是JobStoreTX进行集群化，最后是启动函数和CommandLineRunner的实现：

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class, TransactionAutoConfiguration.class})
public class Application implements CommandLineRunner {

    @Autowired
    private Scheduler scheduler;

    @Autowired
    private JedisProvider jedisProvider;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        // 准备一些测试数据
        prepareOrderMessageData();
        JobDetail job = JobBuilder.newJob(OrderMessageConsumer.class)
                .withIdentity("OrderMessageConsumer", "DelayTask")
                .build();
        // 触发器5秒触发一次
        Trigger trigger = TriggerBuilder.newTrigger()
                .withIdentity("OrderMessageConsumerTrigger", "DelayTask")
                .withSchedule(SimpleScheduleBuilder.simpleSchedule().withIntervalInSeconds(5).repeatForever())
                .build();
        scheduler.scheduleJob(job, trigger);
    }

    private void prepareOrderMessageData() throws Exception {
        DateTimeFormatter f = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
        try (Jedis jedis = jedisProvider.provide()) {
            List messages = Lists.newArrayList();
            for (int i = 0; i < 100; i++) {
                OrderMessage message = new OrderMessage();
                message.setAmount(BigDecimal.valueOf(i));
                message.setOrderId("ORDER_ID_" + i);
                message.setUserId((long) i);
                message.setTimestamp(LocalDateTime.now().format(f));
                messages.add(message);
            }
            // 这里暂时不使用Lua
            Map map = Maps.newHashMap();
            Map hash = Maps.newHashMap();
            for (OrderMessage message : messages) {
                // 故意把score设计成30分钟前
                map.put(message.getOrderId(), Double.valueOf(String.valueOf(System.currentTimeMillis() - 30 * 60 * 1000)));
                hash.put(message.getOrderId(), JSON.toJSONString(message));
            }
            jedis.zadd("ORDER_QUEUE", map);
            jedis.hmset("ORDER_DETAIL_QUEUE", hash);
        }
    }
}

输出结果如下：

2019-08-21 22:45:59.518  INFO 33000 --- [ryBean_Worker-1] club.throwable.OrderMessageConsumer      : 订单消息处理定时任务开始执行......
2019-08-21 22:45:59.525  INFO 33000 --- [onsumerWorker-4] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_91, amount=91, userId=91, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.525  INFO 33000 --- [onsumerWorker-2] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_95, amount=95, userId=95, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.525  INFO 33000 --- [onsumerWorker-1] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_97, amount=97, userId=97, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.525  INFO 33000 --- [onsumerWorker-0] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_99, amount=99, userId=99, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.525  INFO 33000 --- [onsumerWorker-3] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_93, amount=93, userId=93, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.539  INFO 33000 --- [onsumerWorker-2] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_94, amount=94, userId=94, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.539  INFO 33000 --- [onsumerWorker-1] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_96, amount=96, userId=96, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.539  INFO 33000 --- [onsumerWorker-3] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_92, amount=92, userId=92, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.539  INFO 33000 --- [onsumerWorker-0] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_98, amount=98, userId=98, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.539  INFO 33000 --- [onsumerWorker-4] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_90, amount=90, userId=90, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:45:59.540  INFO 33000 --- [ryBean_Worker-1] club.throwable.OrderMessageConsumer      : 订单消息处理定时任务执行完毕,耗时:22 ms......
2019-08-21 22:46:04.515  INFO 33000 --- [ryBean_Worker-2] club.throwable.OrderMessageConsumer      : 订单消息处理定时任务开始执行......
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-5] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_89, amount=89, userId=89, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-6] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_87, amount=87, userId=87, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-7] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_85, amount=85, userId=85, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-5] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_88, amount=88, userId=88, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-2] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_83, amount=83, userId=83, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-1] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_81, amount=81, userId=81, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-6] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_86, amount=86, userId=86, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-2] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_82, amount=82, userId=82, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-7] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_84, amount=84, userId=84, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [onsumerWorker-1] club.throwable.OrderMessageConsumer      : 处理订单信息,内容:OrderMessage(orderId=ORDER_ID_80, amount=80, userId=80, timestamp=2019-08-21 22:45:59.475)
2019-08-21 22:46:04.516  INFO 33000 --- [ryBean_Worker-2] club.throwable.OrderMessageConsumer      : 订单消息处理定时任务执行完毕,耗时:1 ms......
......

首次执行的时候涉及到一些组件的初始化，会比较慢，后面看到由于我们只是简单打印订单信息，所以定时任务执行比较快。如果在不调整当前架构的情况下，生产中需要注意：

• 切换JobStore为JDBC模式，Quartz官方有完整教程，或者看笔者之前翻译的Quartz文档。
• 需要监控或者收集任务的执行状态，添加预警等等。

这里其实有一个性能隐患，命令ZREVRANGEBYSCORE的时间复杂度可以视为为O(N)，N是集合的元素个数，由于这里把所有的订单信息都放进了同一个Sorted Set(ORDER_QUEUE)中，所以在一直有新增数据的时候，dequeue脚本的时间复杂度一直比较高，后续订单量升高之后会此处一定会成为性能瓶颈，后面会给出解决的方案。

小结

这篇文章主要从一个实际生产案例的仿真例子入手，分析了当前延时任务的一些实现方案，还基于Redis和Quartz给出了一个完整的示例。当前的示例只是处于可运行的状态，有些问题尚未解决。下一篇文章会着眼于解决两个方面的问题：

1. 分片。
2. 监控。

还有一点，架构是基于业务形态演进出来的，很多东西需要结合场景进行方案设计和改进，思路仅供参考，切勿照搬代码。

附件

• Markdown和PPT原件：https://github.com/zjcscut/blog-article-file/tree/master/20190821/redis-delay-task-first
• Github Page：http://www.throwable.club/2019/08/21/redis-delay-task-first
• Coding Page：http://throwable.coding.me/2019/08/21/redis-delay-task-first

（本文完 c-5-d e-a-20190821 顺便开通了RSS插件，见主页的图标，欢迎订阅）