guava多线程，futurecallback线程调用不平均

最近查看日志，发现guava的多个futurecallback线程调用不平均，在这里记录一下

Guava Futures简介

Google Guava框架的 com.google.common.util.concurrent包是并发相关的包，它是对JDK自带
concurrent包中Future和线程池相关类的扩展，从而衍生出一些新类，并提供了更为广泛的功能。
在项目中常用的该包中类如下所示：

• ListenableFuture：该接口扩展了Future接口，增加了addListener方法，该方法在给定的excutor上注册一个监听器，当计算完成时会马上调用该监听器。不能够确保监听器执行的顺序，但可以在计算完成时确保马上被调用。
• FutureCallback：该接口提供了OnSuccess和onFailure方法。获取异步计算的结果并回调。
• MoreExecutors：该类是final类型的工具类，提供了很多静态方法。例如listeningDecorator方法初始化ListeningExecutorService方法，使用此实例submit方法即可初始化ListenableFuture对象。
• ListenableFutureTask：该类是一个适配器，可以将其它Future适配成ListenableFuture。
• ListeningExecutorService：该类是对ExecutorService的扩展，重写了ExecutorService类中的submit方法，并返回ListenableFuture对象。
• JdkFutureAdapters：该类扩展了FutureTask类并实现ListenableFuture接口，增加了addListener方法。
• Futures：该类提供和很多实用的静态方法以供使用。

现象

我创建了8个线程，平均处理多任务，但是到最后发现futurecallback调用的线程分部不平均。

日志：

2022-06-10 16:49:23.402 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=4%
2022-06-10 16:49:23.402 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=8%
2022-06-10 16:49:23.402 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=12%
2022-06-10 16:49:23.407 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=16%
2022-06-10 16:49:23.407 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=20%
2022-06-10 16:49:23.409 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=24%
2022-06-10 16:49:23.409 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=28%
2022-06-10 16:49:23.409 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=32%
2022-06-10 16:49:23.411 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=36%
2022-06-10 16:49:23.411 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=40%
2022-06-10 16:49:23.413 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=44%
2022-06-10 16:49:23.413 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=48%
2022-06-10 16:49:23.413 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=52%
2022-06-10 16:49:23.416 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=56%
2022-06-10 16:49:23.416 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=60%
2022-06-10 16:49:23.418 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=64%
2022-06-10 16:49:23.418 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=68%
2022-06-10 16:49:23.418 [pool-7-thread-7] INFO  c.l.AsyncTask - percent=72%
2022-06-10 16:49:25.231 [pool-7-thread-8] INFO  c.l.AsyncTask - percent=76%
2022-06-10 16:49:27.436 [pool-7-thread-2] INFO  c.l.AsyncTask - percent=80%
2022-06-10 16:49:27.970 [pool-7-thread-4] INFO  c.l.AsyncTask - percent=84%
2022-06-10 16:49:31.812 [pool-7-thread-5] INFO  c.l.AsyncTask - percent=88%
2022-06-10 16:49:33.475 [pool-7-thread-6] INFO  c.l.AsyncTask - percent=92%
2022-06-10 16:49:34.184 [pool-7-thread-3] INFO  c.l.AsyncTask - percent=96%
2022-06-10 16:56:56.214 [pool-7-thread-1] INFO  c.l.AsyncTask - percent=100%

参考例子：

ExecutorService executorService = Executors.newSingleThreadExecutor(new ThreadFactory() {
    @Override
    public Thread newThread(Runnable r) {
        Thread t = new Thread(r);
        t.setDaemon(false);
        return t;
    }
});
ListenableFuture<?> listenableFuture = JdkFutureAdapters.listenInPoolThread(
        executorService.submit(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(10000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("run!!!");
            }
        }),
        executorService
);
Futures.addCallback(listenableFuture, new FutureCallback<Object>() {

    @Override
    public void onSuccess(@Nullable Object result) {
        System.out.println("onSuccess");
    }

    @Override
    public void onFailure(Throwable t) {
        System.out.println("onFailure");
    }
});

参考

java - how Futures.addCallback guarantee the callback to be executed at the thread executing the future task? - Stack Overflow

Futures (Guava: Google Core Libraries for Java 23.0 API)

https://stackoverflow.com/questions/35211331/in-which-thread-futurecallback-will-be-called-for-a-listenablefuture-in-guava

https://stackoverflow.com/questions/63629421/listenable-future-callback-is-heavily-delayed