Question

我想在有时间限制的后台执行一些工作。问题是，我不想阻止主线程。

天真的实现是拥有两个执行器服务。一个用于调度/超时，第二个用于完成工作。

final ExecutorService backgroundExecutor = Executors.newSingleThreadExecutor();
final ExecutorService workerExecutor = Executors.newCachedThreadExecutor();


backgroundExecutor.execute(new Runnable() {
    public void run() {
        Future future = workerExecutor.submit(new Runnable() {
            public void run() {
                // do work
            }
        });
        try {
            future.get(120 * 1000, TimeUnit.MILLISECONDS);
        } catch (InterruptedException e) {
            logger.error("InterruptedException while notifyTransactionStateChangeListeners()", e);
            future.cancel(true);
        } catch (ExecutionException e) {
            logger.error("ExecutionException", e);
        } catch (TimeoutException e) {
            logger.error("TimeoutException", e);
            future.cancel(true);
        }
    }
});

还有其他解决方案吗？

Answer 1

您不需要ExecutorService就可以像这样一次运行一个线程。您可以创建一个FutureTask，它可以在不增加开销的情况下为您提供相同的好处。

FutureTask<T> future = new FutureTask<T>(callable);
Thread thread = new Thread(future);
thread.start();
try {
    future.get(120 * 1000, TimeUnit.MILLISECONDS);
} ...

上述代码段中的callable将是您的任务。如果您有Runnable（就像在上面的代码块中那样），您可以通过以下方式将其转换为Callable：

Callable callable = Executors.callable(runnable, null);

因此，总而言之，您的代码可能会更改为：

backgroundExecutor.execute(new Runnable() {
    public void run() {

        Runnable myRunnable = new Runnable() {
            public void run() {
                // do work
            }
        } 

        Callable callable = Executors.callable(myRunnable, null);

        FutureTask<T> future = new FutureTask<T>(callable);
        Thread thread = new Thread(future);
        thread.start();

        try {
            future.get(120 * 1000, TimeUnit.MILLISECONDS);
        } catch (InterruptedException e) {
            logger.error("InterruptedException while notifyTransactionStateChangeListeners()", e);
            future.cancel(true);
        } catch (ExecutionException e) {
            logger.error("ExecutionException", e);
        } catch (TimeoutException e) {
            logger.error("TimeoutException", e);
            future.cancel(true);
        } 
    }
});

您不需要最终关闭执行程序。虽然您可能仍希望最终清理任何其他资源。

Answer 2

您可以将Executor Service与CompletableFuture一起使用。 CompletableFuture runAsync接受Runnable和ExecutorService参数。

final ExecutorService workerExecutor = Executors.newCachedThreadExecutor();

void queueTask(TaskId taskId) {
        workerExecutor.submit(() -> processTaskAsync(taskId));
    }

private void processTaskAsync(TaskId taskId) {
        CompletableFuture.runAsync(() -> processTask(taskId), this.workerExecutor)
                .whenComplete((ok, error) -> {
                    if (error != null) {
                        log.error("Exception while processing task", error);
                    } else {
                        log.info("finished post processing for task id {}", taskId.getValue());
                    }
                });
}

ExecutorService超时而不阻塞主线程

2 个答案: