ExecutorService的java超时而不阻塞主线程

Question

我想在有时间限制的背景下执行一些工作。问题是，我不想阻塞主线程

简单的实现是有两个执行器服务。一个用于调度/超时，另一个负责完成工作

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);
        }
    }
});

还有其他解决办法吗

Answer 1

你不需要一个ExecutorService只运行一个线程一次。您可以创建一个FutureTask，它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);
} ...

上面代码段中的可调用项将是您的任务。 如果您有一个可运行的（正如您在上面的代码块中所做的），您可以通过以下方式将其转换为可调用的：

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

总之，您的代码可以更改为：

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);
        } 
    }
});

你不需要最后一个命令来关闭遗嘱执行人。尽管您可能仍然希望最终清理任何其他资源

Answer 2

您可以将Executor服务与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());
                    }
                });
}