Springboot定时任务原理及如何动态创建定时任务
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);
else
ensurePrestart();
}
}
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 runWorker
this.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-";
} @Override
public 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(); @Override
public 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;
} @PreDestroy
public 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;
} @Override
public void run() {
//设置队列大小10
LOGGER.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;
} @Override
public 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-";
} @Override
public 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 { @Autowired
private DynamicTask dynamicTask; @Test
public 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);
}
}
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