ThreadPoolExecutor : 获取正在执行的特定Runnable

Question

我正在使用 ThreadPoolExecutor 在后台执行多个长运行任务，ThreadPoolExecutor 的池大小为 4，因此当添加超过 4 个任务时，它们将被推送到队列，当 4 个任务之一完成时，从队列中弹出一个任务以供执行。

我想知道有什么方法可以访问 Runnable 当前正在执行但不在队列中的对象，即前 4 个任务。

目标：我想这样做是为了在任何给定点获取任务的当前状态，在 mThreadPoolExecutor.getQueue() 的帮助下，我正在访问正在排队并准备执行的任务，请建议我访问任务的方法这些目前正在执行，以便我可以在需要时附加和删除 listener/handler。

我的可运行class:

public class VideoFileUploadRunner implements Runnable {

    private final VideoFileSync mVideoFileSync;
    private final DataService dataService;

    private Handler handler;

    public VideoFileUploadRunner(VideoFileSync videoFileSync, DataService dataService) {
        this.mVideoFileSync = videoFileSync;
        this.dataService = dataService;

    }

    public int getPK()
    {
        return  mVideoFileSync.get_idPrimaryKey();
    }

    public void setHandler(Handler handler) {
        this.handler = handler;
    }

    @Override
    public void run() {
        try {

            if (mVideoFileSync.get_idPrimaryKey() < 0) {
                addEntryToDataBase();
            }
            updateStatus(VideoUploadStatus.IN_PROGRESS);
            FileUploader uploader = new FileUploader();
            updateStatus(uploader.uploadFile(mVideoFileSync.getVideoFile()));



        } catch (Exception e) {
            updateStatus(VideoUploadStatus.FAILED);
            e.printStackTrace();
        }
    }

    private void addEntryToDataBase() {
        int pk = dataService.saveVideoRecordForSync(mVideoFileSync);
        mVideoFileSync.set_idPrimaryKey(pk);
    }

    private void updateStatus(VideoUploadStatus status) {
        if (handler != null) {
            Message msg = new Message();
            Bundle b = new Bundle();
            b.putString(AppConstants.Sync_Status, status.toString());
            msg.setData(b);
            handler.sendMessage(msg);
        }
        dataService.updateUploadStatus(mVideoFileSync.get_idPrimaryKey(), status.toString());


    }
}

在任务进度列表视图中：

public void setData(VideoFileSync fileSync) {
        tvIso.setText(fileSync.getVideoFile().getISO_LOOP_EQUP());
        tvUnit.setText(fileSync.getVideoFile().getUnit());
        tvName.setText(fileSync.getVideoFile().getLocalPath());
        tvStatus.setText(fileSync.getCurentStatus().toString());
        addHandleForUpdate(fileSync);
    }

    private void addHandleForUpdate(VideoFileSync fileSync) {

        Handler.Callback callBack = new Handler.Callback() {
            @Override
            public boolean handleMessage(Message msg) {
                if(msg.getData()!=null)
                {
                    tvStatus.setText(msg.getData().getString(AppConstants.Sync_Status));

                }
                return false;
            }
        };
        mHadler = new Handler(Looper.getMainLooper(),callBack);

        VideoFileUploadRunner runner = VideoUploadManager.getInstance().getRunnerForSyncFile(fileSync);
        if(runner!=null)
        runner.setHandler(mHadler);
    }

在 VideoUploadManager 中，我有以下 return Runnable 对象的方法，在这里我需要帮助，以便我可以 return 当前正在执行的任务。

public synchronized VideoFileUploadRunner getRunnerForSyncFile(VideoFileSync fileSync) {
        Iterator<Runnable> itr = mThreadPoolExecutor.getQueue().iterator();
        while (itr.hasNext()) {
            VideoFileUploadRunner runner = (VideoFileUploadRunner) itr.next();
            if (runner.getPK() == fileSync.get_idPrimaryKey()) {
                return runner;
            }
        }
        return null;

    }

Answer 1

最好的方法是公开一个同步变量，其中包含有关当前正在执行的任务的信息。

public MyTask implements Runnable {
    private String id;
    private Map<String, MyTask> mapTasks;

    public MyTask(String id, Map<String, MyTask> mapTasks) {
        this.id = id;
        this.mapTasks = mapTasks;
    }

    public void run() {
         synchronized(mapTasks) {
             mapTasks.put(id, this);
         }

         ...

         synchronized(mapTasks) {
             mapTasks.remove(id);
         }
    }
}


// Create a map of tasks
Map<String, MyTask> mapTasks = new HashMap<String, MyTask>();

// How to create tasks
MyTask myTask1 = new MyTask("task1", mapTasks);
MyTask myTask2 = new MyTask("task2", mapTasks);

executorService.execute(myTask1);
executorService.execute(myTask2);

....

并打印当前正在执行的任务列表：

public void printCurrentExecutingTasks(Map<String, MyTask> tasks) {
    for (String id: tasks.keySet()) {
        System.out.println("Executing task with id: " + id);
    }
}

Answer 2

我的回答集中在问题上："how to know which runnables are being executed".

这种方法保留一组并发的活动 Runnable：

private final Set<VideoFileUploadRunner> active = Collections.newSetFromMap(new ConcurrentHashMap<>());

提交给 ThreadPoolExecutor 的 Runnable 应该用更新此集合的 Runnable 装饰：

class DecoratedRunnable implements Runnable {

    final VideoFileUploadRunner runnable;

    public DecoratedRunnable(VideoFileUploadRunner runnable) {
        this.runnable = runnable;
    }

    @Override
    public void run() {
        active.add(runnable); // add to set
        try {
            runnable.run();
        } finally {
            active.remove(runnable); // finally remove from set (even when something goes wrong)
        }
    }
}

所以我们可以在提交之前装饰 VideoFileUploadRunner 个实例：

executorService.submit(new DecoratedRunnable(videoFileUploadRunner));

方法 getRunnerForSyncFile 将像这样简单地实现：

public VideoFileUploadRunner getRunnerForSyncFile(VideoFileSync fileSync) {
    return active.stream()
            .filter(videoFileUploadRunner -> videoFileUploadRunner.getPK() == fileSync.get_idPrimaryKey())
            .findAny()
            .orElse(null);
}

Remark ：正如@Charlie 评论的那样，这不是将侦听器附加到 Runnable 的最佳方式。您可以请求从 VideoFileUploadRunner 的 run() 方法内部设置消息处理程序，或者使用 MessageHandler 集初始化此类实例，或者使用这种装饰方法使其远离 VideoFileUploadRunner class.

Answer 3

这个答案与我上面的评论有关。

与其尝试通过执行器找到运行nable 并为其附加一个侦听器，不如在创建运行nable 和 post 事件时将侦听器绑定到运行nable从运行nable 的执行代码到监听器。

只有当前活跃的运行启用才会 post 他们的更新。

这是一个例子。

为您的侦听器创建一个接口来实现。您的监听器可以是线程池执行器、私有内部 class 等

/** 
 * Callback interface to notify when a video upload's state changes 
 */
interface IVideoUploadListener {

    /**
     * Called when a video upload's state changes

     * @param pUploadId The ID of the video upload
     * @param pStatus The new status of the upload
     */
    void onStatusChanged(int pUploadId, VideoUploadStatus pStatus);
}

为您的状态类型创建枚举（例如）

/**
 * Enum to hold different video upload states
 */
enum VideoUploadStatus {
    IN_PROGRESS,
    ADDED_TO_DB,
    FILE_UPLOADED,
    FINISHED,
    FAILED
}

在每个 Runnable 中保存监听器的引用。

public class VideoFileUploadRunner implements Runnable {

    private final IVideoUploadListener mUploadListener;
    private final VideoFileSync mVideoFileSync;
    private final DataService   mDataService;
    private Handler mHandler;

    // etc...
}

通过构造函数传递一个接口实例

public VideoFileUploadRunner(IVideoUploadListener pUploadListener, VideoFileSync pVideoFileSync, DataService pDataService) {
    mUploadListener = pUploadListener;
    mVideoFileSync  = pVideoFileSync;
    mDataService    = pDataService;
}

在运行方法中，post 根据需要更新侦听器。

@Override
public void run() {
    mUploadListener.onStatusChanged(getPrimaryKey(), VideoUploadStatus.IN_PROGRESS);
    try {
        if (mVideoFileSync.get_idPrimaryKey() < 0) {
            addEntryToDataBase();
            mUploadListener.onStatusChanged(getPrimaryKey(), VideoUploadStatus.ADDED_TO_DB);
        }
        FileUploader uploader = new FileUploader();
        uploader.uploadFile(mVideoFileSync.getVideoFile());
        mUploadListener.onStatusChanged(getPrimaryKey(), VideoUploadStatus.FILE_UPLOADED);

        // Other logic here...

        mUploadListener.onStatusChanged(getPrimaryKey(), VideoUploadStatus.FINISHED);
    }

    catch (Exception e) {
        mUploadListener.onStatusChanged(getPrimaryKey(), VideoUploadStatus.FAILED);
        e.printStackTrace();
    }
}

onStatusChanged() 方法的侦听器实现应该同步。这将有助于避免竞争条件导致的错误结果。

private IVideoUploadListener mUploadListener = new IVideoUploadListener() {
    @Override
    public synchronized void onStatusChanged(int pUploadId, VideoUploadStatus pStatus) {
        Log.i("ListenerTag", "Video file with ID " + pUploadId + " has the status " + pStatus.toString());
    }
};

ThreadPoolExecutor : 获取正在执行的特定Runnable

ThreadPoolExecutor : Get a specific Runnable that is being executed

java

multithreading

android

runnable

threadpoolexecutor