一、前言
上周工作遇到了一个需求，同步多个省份销号数据，解绑微信粉丝。分省定时将销号数据放到SFTP服务器上，我需要开发定时任务去解析文件。因为是多省份，服务器、文件名规则、数据规则都不一定，所以要做成可配置是有一定难度的。数据规则这块必须强烈要求统一，服务器、文件名规则都可以从配置中心去读。每新增一个省份的配置，后台感知到后，动态生成定时任务。
二、Springboot引入定时任务核心配置
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Import(SchedulingConfiguration.class) @Documented public @interface EnableScheduling {}@Configuration @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public class SchedulingConfiguration {@Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)@Role(BeanDefinition.ROLE_INFRASTRUCTURE)public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {return new ScheduledAnnotationBeanPostProcessor();}}
接下来主要看一下这个核心后置处理器：ScheduledAnnotationBeanPostProcessor 。
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {if (bean instanceof AopInfrastructureBean || bean instanceof TaskScheduler ||bean instanceof ScheduledExecutorService) {// Ignore AOP infrastructure such as scoped proxies.return bean;}Class<?> targetClass = AopProxyUtils.ultimateTargetClass(bean); if (!this.nonAnnotatedClasses.contains(targetClass)) { Map<Method, Set<Scheduled>> annotatedMethods = MethodIntrospector.selectMethods(targetClass, (MethodIntrospector.MetadataLookup<Set<Scheduled>>) method -> { Set<Scheduled> scheduledMethods = AnnotatedElementUtils.getMergedRepeatableAnnotations( method, Scheduled.class, Schedules.class); return (!scheduledMethods.isEmpty() ? scheduledMethods : null); }); if (annotatedMethods.isEmpty()) { this.nonAnnotatedClasses.add(targetClass); if (logger.isTraceEnabled()) { logger.trace("No @Scheduled annotations found on bean class: " + targetClass); } } else { // Non-empty set of methods annotatedMethods.forEach((method, scheduledMethods) -> scheduledMethods.forEach(scheduled -> processScheduled(scheduled, method, bean))); if (logger.isTraceEnabled()) { logger.trace(annotatedMethods.size() + " @Scheduled methods processed on bean '" + beanName + "': " + annotatedMethods); } } } return bean; } 1、处理Scheduled注解，通过ScheduledTaskRegistrar注册定时任务。
private void finishRegistration() {if (this.scheduler != null) {this.registrar.setScheduler(this.scheduler);}if (this.beanFactory instanceof ListableBeanFactory) {Map<String, SchedulingConfigurer> beans =((ListableBeanFactory) this.beanFactory).getBeansOfType(SchedulingConfigurer.class);List<SchedulingConfigurer> configurers = new ArrayList<>(beans.values());AnnotationAwareOrderComparator.sort(configurers);for (SchedulingConfigurer configurer : configurers) {configurer.configureTasks(this.registrar);}}if (this.registrar.hasTasks() && this.registrar.getScheduler() == null) {Assert.state(this.beanFactory != null, "BeanFactory must be set to find scheduler by type");try {// Search for TaskScheduler bean...this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, false));}catch (NoUniqueBeanDefinitionException ex) {logger.trace("Could not find unique TaskScheduler bean", ex);try {this.registrar.setTaskScheduler(resolveSchedulerBean(this.beanFactory, TaskScheduler.class, true));}catch (NoSuchBeanDefinitionException ex2) {if (logger.isInfoEnabled()) {logger.info("More than one TaskScheduler bean exists within the context, and " +"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +ex.getBeanNamesFound());}}}catch (NoSuchBeanDefinitionException ex) {logger.trace("Could not find default TaskScheduler bean", ex);// Search for ScheduledExecutorService bean next...try {this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, false));}catch (NoUniqueBeanDefinitionException ex2) {logger.trace("Could not find unique ScheduledExecutorService bean", ex2);try {this.registrar.setScheduler(resolveSchedulerBean(this.beanFactory, ScheduledExecutorService.class, true));}catch (NoSuchBeanDefinitionException ex3) {if (logger.isInfoEnabled()) {logger.info("More than one ScheduledExecutorService bean exists within the context, and " +"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +ex2.getBeanNamesFound());}}}catch (NoSuchBeanDefinitionException ex2) {logger.trace("Could not find default ScheduledExecutorService bean", ex2);// Giving up -> falling back to default scheduler within the registrar...logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing");}}}this.registrar.afterPropertiesSet(); }
1、通过一系列的SchedulingConfigurer动态配置ScheduledTaskRegistrar。
2、向ScheduledTaskRegistrar注册一个TaskScheduler（用于对Runnable的任务进行调度，它包含有多种触发规则）。
3、registrar.afterPropertiesSet()，在这开始安排所有的定时任务开始执行了。
protected void scheduleTasks() {if (this.taskScheduler == null) {this.localExecutor = Executors.newSingleThreadScheduledExecutor();this.taskScheduler = new ConcurrentTaskScheduler(this.localExecutor);}if (this.triggerTasks != null) {for (TriggerTask task : this.triggerTasks) {addScheduledTask(scheduleTriggerTask(task));}}if (this.cronTasks != null) {for (CronTask task : this.cronTasks) {addScheduledTask(scheduleCronTask(task));}}if (this.fixedRateTasks != null) {for (IntervalTask task : this.fixedRateTasks) {addScheduledTask(scheduleFixedRateTask(task));}}if (this.fixedDelayTasks != null) {for (IntervalTask task : this.fixedDelayTasks) {addScheduledTask(scheduleFixedDelayTask(task));}} }
1、TriggerTask：动态定时任务。通过Trigger#nextExecutionTime 给定的触发上下文确定下一个执行时间。
2、CronTask：动态定时任务，TriggerTask子类。通过cron表达式确定的时间触发下一个任务执行。
3、IntervalTask：一定时间延迟之后，周期性执行的任务。
4、taskScheduler 如果为空，默认是ConcurrentTaskScheduler，并使用默认单线程的ScheduledExecutor。
三、主要看一下CronTask工作原理
ScheduledTaskRegistrar.java @Nullable public ScheduledTask scheduleCronTask(CronTask task) {ScheduledTask scheduledTask = this.unresolvedTasks.remove(task);boolean newTask = false;if (scheduledTask == null) {scheduledTask = new ScheduledTask(task);newTask = true;}if (this.taskScheduler != null) {scheduledTask.future = this.taskScheduler.schedule(task.getRunnable(), task.getTrigger());}else {addCronTask(task);this.unresolvedTasks.put(task, scheduledTask);}return (newTask ? scheduledTask : null); }ConcurrentTaskScheduler.java @Override @Nullable public ScheduledFuture<?> schedule(Runnable task, Trigger trigger) {try {if (this.enterpriseConcurrentScheduler) {return new EnterpriseConcurrentTriggerScheduler().schedule(decorateTask(task, true), trigger);}else {ErrorHandler errorHandler =(this.errorHandler != null ? this.errorHandler : TaskUtils.getDefaultErrorHandler(true));return new ReschedulingRunnable(task, trigger, this.scheduledExecutor, errorHandler).schedule();}}catch (RejectedExecutionException ex) {throw new TaskRejectedException("Executor [" + this.scheduledExecutor + "] did not accept task: " + task, ex);} }ReschedulingRunnable.java @Nullable public ScheduledFuture<?> schedule() {synchronized (this.triggerContextMonitor) {this.scheduledExecutionTime = this.trigger.nextExecutionTime(this.triggerContext);if (this.scheduledExecutionTime == null) {return null;}long initialDelay = this.scheduledExecutionTime.getTime() - System.currentTimeMillis();this.currentFuture = this.executor.schedule(this, initialDelay, TimeUnit.MILLISECONDS);return this;} }private ScheduledFuture<?> obtainCurrentFuture() {Assert.state(this.currentFuture != null, "No scheduled future");return this.currentFuture; }@Override public void run() {Date actualExecutionTime = new Date();super.run();Date completionTime = new Date();synchronized (this.triggerContextMonitor) {Assert.state(this.scheduledExecutionTime != null, "No scheduled execution");this.triggerContext.update(this.scheduledExecutionTime, actualExecutionTime, completionTime);if (!obtainCurrentFuture().isCancelled()) {schedule();}} }
1、最终将task和trigger都封装到了ReschedulingRunnable中。
2、ReschedulingRunnable实现了任务重复调度（schedule方法中调用调度器executor并传入自身对象，executor会调用run方法，run方法又调用了schedule方法）。
3、ReschedulingRunnable schedule方法加了同步锁，只能有一个线程拿到下次执行时间并加入执行器的调度。
4、不同的ReschedulingRunnable对象之间在线程池够用的情况下是不会相互影响的，也就是说满足线程池的条件下，TaskScheduler的schedule方法的多次调用是可以交叉执行的。
ScheduledThreadPoolExecutor.java public ScheduledFuture<?> schedule(Runnable command,long delay,TimeUnit unit) {if (command == null || unit == null)throw new NullPointerException();RunnableScheduledFuture<?> t = decorateTask(command,new ScheduledFutureTask<Void>(command, null,triggerTime(delay, unit)));delayedExecute(t);return t; }private void delayedExecute(RunnableScheduledFuture<?> task) {if (isShutdown())reject(task);else {super.getQueue().add(task);if (isShutdown() &&!canRunInCurrentRunState(task.isPeriodic()) &&remove(task))task.cancel(false);elseensurePrestart();} }
ScheduledFutureTask 工作原理如下图所示【太懒了，不想画图了，盗图一张】。
1、ScheduledFutureTask会放入优先阻塞队列：ScheduledThreadPoolExecutor.DelayedWorkQueue（二叉最小堆实现）
2、上图中的Thread对象即ThreadPoolExecutor.Worker，实现了Runnable接口
/*** Creates with given first task and thread from ThreadFactory.* @param firstTask the first task (null if none)*/ Worker(Runnable firstTask) {setState(-1); // inhibit interrupts until runWorkerthis.firstTask = firstTask;this.thread = getThreadFactory().newThread(this); }/** Delegates main run loop to outer runWorker */ public void run() {runWorker(this); }
1、Worker中维护了Thread对象，Thread对象的Runnable实例即Worker自身
2、ThreadPoolExecutor#addWorker方法中会创建Worker对象，然后拿到Worker中的thread实例并start，这样就创建了线程池中的一个线程实例
3、Worker的run方法会调用ThreadPoolExecutor#runWorker方法，这才是任务最终被执行的地方，该方法示意如下
（1）首先取传入的task执行，如果task是null，只要该线程池处于运行状态，就会通过getTask方法从workQueue中取任务。ThreadPoolExecutor的execute方法会在无法产生core线程的时候向 workQueue队列中offer任务。
getTask方法从队列中取task的时候会根据相关配置决定是否阻塞和阻塞多久。如果getTask方法结束，返回的是null，runWorker循环结束，执行processWorkerExit方法。
至此，该线程结束自己的使命，从线程池中“消失”。
（2）在开始执行任务之前，会调用Worker的lock方法，目的是阻止task正在被执行的时候被interrupt，通过调用clearInterruptsForTaskRun方法来保证的(后面可以看一下这个方法)，该线程没有自己的interrupt set了。
（3）beforeExecute和afterExecute方法用于在执行任务前后执行一些自定义的操作，这两个方法是空的，留给继承类去填充功能。
我们可以在beforeExecute方法中抛出异常，这样task不会被执行，而且在跳出该循环的时候completedAbruptly的值是true，表示the worker died due to user exception，会用decrementWorkerCount调整wc。
（4）因为Runnable的run方法不能抛出Throwables异常，所以这里重新包装异常然后抛出，抛出的异常会使当当前线程死掉，可以在afterExecute中对异常做一些处理。
（5）afterExecute方法也可能抛出异常，也可能使当前线程死掉。
四、动态创建定时任务
TaskConfiguration 配置类
@Configuration @EnableScheduling @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public class TaskConfiguration {@Bean(name = ScheduledAnnotationBeanPostProcessor.DEFAULT_TASK_SCHEDULER_BEAN_NAME)@Role(BeanDefinition.ROLE_INFRASTRUCTURE)public ScheduledExecutorService scheduledAnnotationProcessor() {return Executors.newScheduledThreadPool(5, new DefaultThreadFactory());}private static class DefaultThreadFactory implements ThreadFactory {private static final AtomicInteger poolNumber = new AtomicInteger(1);private final ThreadGroup group;private final AtomicInteger threadNumber = new AtomicInteger(1);private final String namePrefix;DefaultThreadFactory() {SecurityManager s = System.getSecurityManager();group = (s != null) ? s.getThreadGroup() :Thread.currentThread().getThreadGroup();namePrefix = "pool-" +poolNumber.getAndIncrement() +"-schedule-";}@Overridepublic Thread newThread(Runnable r) {Thread t = new Thread(group, r,namePrefix + threadNumber.getAndIncrement(),0);if (t.isDaemon()) {t.setDaemon(false);}if (t.getPriority() != Thread.NORM_PRIORITY) {t.setPriority(Thread.NORM_PRIORITY);}return t;}} }
1、保证ConcurrentTaskScheduler不使用默认单线程的ScheduledExecutor，而是corePoolSize=5的线程池
2、自定义线程池工厂类
DynamicTask 动态定时任务
@Configuration public class DynamicTask implements SchedulingConfigurer {private static Logger LOGGER = LoggerFactory.getLogger(DynamicTask.class);private static final ExecutorService es = new ThreadPoolExecutor(10, 20,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue<>(10),new DynamicTaskConsumeThreadFactory());private volatile ScheduledTaskRegistrar registrar;private final ConcurrentHashMap<String, ScheduledFuture<?>> scheduledFutures = new ConcurrentHashMap<>();private final ConcurrentHashMap<String, CronTask> cronTasks = new ConcurrentHashMap<>();private volatile List<TaskConstant> taskConstants = Lists.newArrayList();@Overridepublic void configureTasks(ScheduledTaskRegistrar registrar) {this.registrar = registrar;this.registrar.addTriggerTask(() -> {if (!CollectionUtils.isEmpty(taskConstants)) {LOGGER.info("检测动态定时任务列表...");List<TimingTask> tts = new ArrayList<>();taskConstants.forEach(taskConstant -> {TimingTask tt = new TimingTask();tt.setExpression(taskConstant.getCron());tt.setTaskId("dynamic-task-" + taskConstant.getTaskId());tts.add(tt);});this.refreshTasks(tts);}}, triggerContext -> new PeriodicTrigger(5L, TimeUnit.SECONDS).nextExecutionTime(triggerContext));}public List<TaskConstant> getTaskConstants() {return taskConstants;}private void refreshTasks(List<TimingTask> tasks) {//取消已经删除的策略任务Set<String> taskIds = scheduledFutures.keySet();for (String taskId : taskIds) {if (!exists(tasks, taskId)) {scheduledFutures.get(taskId).cancel(false);}}for (TimingTask tt : tasks) {String expression = tt.getExpression();if (StringUtils.isBlank(expression) || !CronSequenceGenerator.isValidExpression(expression)) {LOGGER.error("定时任务DynamicTask cron表达式不合法: " + expression);continue;}//如果配置一致，则不需要重新创建定时任务if (scheduledFutures.containsKey(tt.getTaskId())&& cronTasks.get(tt.getTaskId()).getExpression().equals(expression)) {continue;}//如果策略执行时间发生了变化，则取消当前策略的任务if (scheduledFutures.containsKey(tt.getTaskId())) {scheduledFutures.remove(tt.getTaskId()).cancel(false);cronTasks.remove(tt.getTaskId());}CronTask task = new CronTask(tt, expression);ScheduledFuture<?> future = registrar.getScheduler().schedule(task.getRunnable(), task.getTrigger());cronTasks.put(tt.getTaskId(), task);scheduledFutures.put(tt.getTaskId(), future);}}private boolean exists(List<TimingTask> tasks, String taskId) {for (TimingTask task : tasks) {if (task.getTaskId().equals(taskId)) {return true;}}return false;}@PreDestroypublic void destroy() {this.registrar.destroy();}public static class TaskConstant {private String cron;private String taskId;public String getCron() {return cron;}public void setCron(String cron) {this.cron = cron;}public String getTaskId() {return taskId;}public void setTaskId(String taskId) {this.taskId = taskId;}}private class TimingTask implements Runnable {private String expression;private String taskId;public String getTaskId() {return taskId;}public void setTaskId(String taskId) {this.taskId = taskId;}@Overridepublic void run() {//设置队列大小10LOGGER.error("当前CronTask: " + this);DynamicBlockingQueue queue = new DynamicBlockingQueue(3);es.submit(() -> {while (!queue.isDone() || !queue.isEmpty()) {try {String content = queue.poll(500, TimeUnit.MILLISECONDS);if (StringUtils.isBlank(content)) {return;}LOGGER.info("DynamicBlockingQueue 消费：" + content);TimeUnit.MILLISECONDS.sleep(500);} catch (InterruptedException e) {e.printStackTrace();}}});//队列放入数据for (int i = 0; i < 5; ++i) {try {queue.put(String.valueOf(i));LOGGER.info("DynamicBlockingQueue 生产：" + i);} catch (InterruptedException e) {e.printStackTrace();}}queue.setDone(true);}public String getExpression() {return expression;}public void setExpression(String expression) {this.expression = expression;}@Overridepublic String toString() {return ReflectionToStringBuilder.toString(this, ToStringStyle.JSON_STYLE, false, false, TimingTask.class);}}/*** 队列消费线程工厂类*/private static class DynamicTaskConsumeThreadFactory implements ThreadFactory {private static final AtomicInteger poolNumber = new AtomicInteger(1);private final ThreadGroup group;private final AtomicInteger threadNumber = new AtomicInteger(1);private final String namePrefix;DynamicTaskConsumeThreadFactory() {SecurityManager s = System.getSecurityManager();group = (s != null) ? s.getThreadGroup() :Thread.currentThread().getThreadGroup();namePrefix = "pool-" +poolNumber.getAndIncrement() +"-dynamic-task-";}@Overridepublic Thread newThread(Runnable r) {Thread t = new Thread(group, r,namePrefix + threadNumber.getAndIncrement(),0);if (t.isDaemon()) {t.setDaemon(false);}if (t.getPriority() != Thread.NORM_PRIORITY) {t.setPriority(Thread.NORM_PRIORITY);}return t;}}private static class DynamicBlockingQueue extends LinkedBlockingQueue<String> {DynamicBlockingQueue(int capacity) {super(capacity);}private volatile boolean done = false;public boolean isDone() {return done;}public void setDone(boolean done) {this.done = done;}} }
1、taskConstants 动态任务列表
2、ScheduledTaskRegistrar#addTriggerTask 添加动态周期定时任务，检测动态任务列表的变化
CronTask task = new CronTask(tt, expression);
ScheduledFuture<?> future = registrar.getScheduler().schedule(task.getRunnable(), task.getTrigger());
cronTasks.put(tt.getTaskId(), task);
scheduledFutures.put(tt.getTaskId(), future);
3、动态创建cron定时任务，拿到ScheduledFuture实例并缓存起来
4、在刷新任务列表时，通过缓存的ScheduledFuture实例和CronTask实例，来决定是否取消、移除失效的动态定时任务。
DynamicTaskTest 动态定时任务测试类
@RunWith(SpringRunner.class) @SpringBootTest public class DynamicTaskTest {@Autowiredprivate DynamicTask dynamicTask;@Testpublic void test() throws InterruptedException {List<DynamicTask.TaskConstant> taskConstans = dynamicTask.getTaskConstants();DynamicTask.TaskConstant taskConstant = new DynamicTask.TaskConstant();taskConstant.setCron("0/5 * * * * ?");taskConstant.setTaskId("test1");taskConstans.add(taskConstant);DynamicTask.TaskConstant taskConstant1 = new DynamicTask.TaskConstant();taskConstant1.setCron("0/5 * * * * ?");taskConstant1.setTaskId("test2");taskConstans.add(taskConstant1);DynamicTask.TaskConstant taskConstant2 = new DynamicTask.TaskConstant();taskConstant2.setCron("0/5 * * * * ?");taskConstant2.setTaskId("test3");taskConstans.add(taskConstant2);TimeUnit.SECONDS.sleep(40);//移除并添加新的配置taskConstans.remove(taskConstans.size() - 1);DynamicTask.TaskConstant taskConstant3 = new DynamicTask.TaskConstant();taskConstant3.setCron("0/5 * * * * ?");taskConstant3.setTaskId("test4");taskConstans.add(taskConstant3); // TimeUnit.MINUTES.sleep(50);} }
