当scheduleWithFixedDelay抛出异常时如何重新启动计划？ [英] How to restart schedule when scheduleWithFixedDelay throws an exception?

问题描述

我使用 ScheduledExecutorService 来计划一些需要定期运行的任务。
我想知道这个代码是否在异常发生时恢复调度。

I use ScheduledExecutorService to schedule some tasks which need to run periodically. I want to know whether this code works to recover the schedule when an exception happens.

ScheduledExecutorService service = Executors.newScheduledThreadPool(1);
this.startMemoryUpdateSchedule(service);//See below method

//Recursive method to handle exception when run schedule task
private void startMemoryUpdateSchedule(ScheduledExecutorService service) {
    ScheduledFuture<?> future = service.scheduleWithFixedDelay(new MemoryUpdateThread(), 1, UPDATE_MEMORY_SCHEDULE, TimeUnit.MINUTES);
    try {
        future.get();
    } catch (ExecutionException e) {
        e.printStackTrace();
        logger.error("Exception thrown for thread",e);
        future.cancel(true);
        this.startMemoryUpdateSchedule(service);
    } catch(Exception e) {
        logger.error("Other exception ",e);
    }
}

推荐答案

应该在 while（true）循环中包含try块，因为如果第一次运行不抛出异常，您将退出您的方法，如果第二次调用抛出一个异常，你不会捕获它。

You should probably enclose the try block in a while(true) loop because if the first run does not throw an exception, you will exit your method and if the second call throws one, you won't catch it.

我也会在自己的线程中运行递归调用，以避免在事情变坏时出现StackOverFlow错误。

I would also run the recursive call in its own thread to avoid the risk of a StackOverFlow error if things go bad.

所以它看起来像这样：

private void startMemoryUpdateSchedule(final ScheduledExecutorService service) {
    final ScheduledFuture<?> future = service.scheduleWithFixedDelay(new MemoryUpdateThread(), 1, UPDATE_MEMORY_SCHEDULE, TimeUnit.MINUTES);
    Runnable watchdog = new Runnable() {

        @Override
        public void run() {
            while (true) {
                try {
                    future.get();
                } catch (ExecutionException e) {
                    //handle it
                    startMemoryUpdateSchedule(service);
                    return;
                } catch (InterruptedException e) {
                    //handle it
                    return;
                }
            }
        }
    };
    new Thread(watchdog).start();
}

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