Java执行器部分关闭

Question

让我们在应用程序中拥有一个经典的Executor。应用程序的许多部分都使用这个执行器进行一些计算，每个计算都可以取消，为此我可以在执行器上调用 shutdown() 或 shutdownNow() 。

但我只想关闭 Executor 中的部分任务。遗憾的是，我无法访问 Future 对象，它们是计算实现的私有(private)部分(实际上计算由 Actor 框架 jetlang 支持)

我想要像 Executor 包装器这样的东西，我可以将其传递给计算，并且应该由真正的 Executor 支持。像这样的事情:

// main application executor
Executor applicationExecutor = Executors.newCachedThreadPool();

// starting computation
Executor computationExecutor = new ExecutorWrapper(applicationExecutor);
Computation computation = new Computation(computationExecutor);
computation.start();

// cancelling computation
computation.cancel();
// shutting down only computation tasks
computationExecutor.shutdown();

// applicationExecutor remains running and happy

或者还有其他想法吗？

Answer 1

对于那些想要好的结果的人:有最终的解决方案，部分基于 Ivan Sopov 的答案。幸运的是，jetlang 仅使用 Executor 接口(interface)(而不是 ExecutorService)来运行其任务，因此我创建了支持停止仅由该包装器创建的任务的包装器类。

static class StoppableExecutor implements Executor {
    final ExecutorService executor;
    final List<Future<?>> futures = Lists.newArrayList();
    boolean stopped;

    public StoppableExecutor(ExecutorService executor) {
        this.executor = executor;
    }

    void stop() {
        this.stopped = true;
        synchronized (futures) {
            for (Iterator<Future<?>> iterator = futures.iterator(); iterator.hasNext();) {
                Future<?> future = iterator.next();
                if (!future.isDone() && !future.isCancelled()) {
                    System.out.println(future.cancel(true));
                }
            }
            futures.clear();
        }
    }

    @Override
    public void execute(Runnable command) {
        if (!stopped) {
            synchronized (futures) {
                Future<?> newFuture = executor.submit(command);
                for (Iterator<Future<?>> iterator = futures.iterator(); iterator.hasNext();) {
                    Future<?> future = iterator.next();
                    if (future.isDone() || future.isCancelled())
                        iterator.remove();
                }
                futures.add(newFuture);
            }
        }
    }
}

使用它非常简单:

ExecutorService service = Executors.newFixedThreadPool(5);
StoppableExecutor executor = new StoppableExecutor(service);

// doing some actor stuff with executor instance
PoolFiberFactory factory = new PoolFiberFactory(executor);

// stopping tasks only created on executor instance
// executor service is happily running other tasks
executor.stop();

仅此而已。效果很好。