扩展Spring Scheduler的执行逻辑

Spring Scheduler因为是单线程执行，所以容易出现部分任务耗时太长，虽然可以使用多线程的方式来提升效率，但是也担心定时任务占用太多的资源，所以还是尽可能地优化定时任务的耗时，那我们首先就可以对耗时进行监控

Spring Scheduler使用ScheduledAnnotationBeanPostProcessor#createRunnable来创建定时任务的执行Runnable（实际类型是ScheduledMethodRunnable），那么我们就可以对该ScheduledMethodRunnable进行扩展，增加任务耗时，设置traceId，方便进行日志分析等

扩展ScheduledMethodRunnable

• 设置traceId
• 监控耗时

@Slf4j
public class TenmaoScheduledMethodRunnable extends ScheduledMethodRunnable {
    public TenmaoScheduledMethodRunnable(Object target, Method method) {
        super(target, method);
    }

    public TenmaoScheduledMethodRunnable(Object target, String methodName) throws NoSuchMethodException {
        super(target, methodName);
    }

    @Override
    public void run() {
        //设置traceId，方便进行日志跟踪
        MDC.put("traceId", UUID.randomUUID().toString().replaceAll("-", ""));
        log.info("{}: start to run", getMethod());
        long startMillis = System.currentTimeMillis();
        try {
            super.run();
        } finally {
            //监控耗时
            long endMillis = System.currentTimeMillis();
            log.info("{}: cost {} millis", getMethod(), endMillis - startMillis);
            MDC.remove("traceId");
        }
    }
}

扩展ScheduledAnnotationBeanPostProcessor

让ScheduledAnnotationBeanPostProcessor使用TenmaoScheduledMethodRunnable作为定时任务真正的执行逻辑

@Component
public class TenmaoScheduledAnnotationBeanPostProcessor extends ScheduledAnnotationBeanPostProcessor {
    @Override
    protected Runnable createRunnable(Object target, Method method) {
        //这两行代码从ScheduledAnnotationBeanPostProcessor#createRunnable复制过来
        Assert.isTrue(method.getParameterCount() == 0, "Only no-arg methods may be annotated with @Scheduled");
        Method invocableMethod = AopUtils.selectInvocableMethod(method, target.getClass());
        
        //把ScheduledMethodRunnable替换为TenmaoScheduledMethodRunnable
        return new TenmaoScheduledMethodRunnable(target, invocableMethod);
    }
}

注意

• 如果没有在TenmaoScheduledAnnotationBeanPostProcessor增加@Component注解，那么@EnableScheduling一定要去掉

思考

• 是不是也可以使用Aop的方式实现这一点呢？ 貌似有一点麻烦，因为很多定时任务是private，并不会被代理

参考

• Spring Boot Multi Thread Scheduling