java - 监控、调试和跟踪 CompletableFuture 任务

Question

我想在使用 CompletableFuture 时监控、跟踪和调试我的任务，例如在以下代码中：

CompletableFuture.supplyAsync(() -> 2)
    .thenApply(i -> i*2)
    .thenAccept(i -> System.out.println("i = " + i));

CompletableFuture.AsynchronousCompletionTask的 Javadoc看起来很有希望，但不清楚如何使用它：

标识由 async 方法生成的异步任务的标记接口。这对于监视、调试和跟踪异步活动可能很有用。

Answer 1

传递给 executor 的 Runnables 不会是原始的 Runnables，它们将被包装到一个实现 AsynchronousCompletionTask 的类中，这使得跟踪成为可能，如下代码所示：

public class Main {
    private static final Executor tracker = new TrackingExecutor(ForkJoinPool.commonPool());

    public static void main(String[] args) throws InterruptedException {
        CompletableFuture.supplyAsync(() -> 2, tracker)
            .thenApply(i -> i*2)
            .thenAccept(i -> System.out.println("i = " + i));
        Thread.sleep(1000);
    }
}

class TrackingExecutor implements Executor {
    private Executor delegate;

    public TrackingExecutor(Executor delegate) {
        this.delegate = delegate;
    }

    @Override
    public void execute(Runnable task) {
        if(task instanceof CompletableFuture.AsynchronousCompletionTask) {
            System.out.println("executing CompletableFuture task");
        }
        delegate.execute(task);
    }
}