Jak uruchomić zaległe zadania zaraz po ExecutorService.shutdown()?

Question

Mam ScheduledExecutorService z zadaniami zaplanowanymi do wykonania w ciągu godziny. Jak uzyskać listę zaległych zadań, aby móc je natychmiast uruchomić?

wierzę shutdown() będzie czekać godzinę i wygląda jakby shutdownNow() zwraca listę Runnables że nie można run(), ponieważ Runnable realizacja sprawdza stan Executor i gdy zauważy, że ma wyłączyć Runnable odmawia uruchomienia . Zobacz ScheduledThreadPoolExecutor.ScheduledFutureTask.run() dla rzeczywistej realizacji.

Wszelkie pomysły?

Answer 1

Wziąłem odpowiedź Mark Peters, realizując wszystkie metody abstrakcyjne, dodał wątku bezpieczeństwa i starał poszanowaniem podstawowej konfiguracji ScheduledThreadPoolExecutor miarę możliwości.

/** 
* Overrides shutdown() to run outstanding tasks immediately. 
* 
* @author Gili Tzabari 
*/ 
public class RunOnShutdownScheduledExecutorService extends AbstractExecutorService 
    implements ScheduledExecutorService 
{ 
    private final ScheduledExecutorService delegate; 
    private final ScheduledThreadPoolExecutor scheduledThreadPoolExecutor; 
    private final ExecutorService immediateService; 
    private final ConcurrentMap<Future<?>, Callable<?>> tasks = Maps.newConcurrentMap(); 

    /** 
    * Creates a new RunOnShutdownScheduledExecutorService. 
    * 
    * @param delegate the executor to delegate to 
    */ 
    public RunOnShutdownScheduledExecutorService(ScheduledExecutorService delegate) 
    { 
     Preconditions.checkNotNull(delegate, "delegate may not be null"); 

     this.delegate = delegate; 
     if (delegate instanceof ScheduledThreadPoolExecutor) 
     { 
      this.scheduledThreadPoolExecutor = (ScheduledThreadPoolExecutor) delegate; 
      this.immediateService = Executors.newFixedThreadPool(scheduledThreadPoolExecutor. 
       getCorePoolSize(), scheduledThreadPoolExecutor.getThreadFactory()); 
     } 
     else 
     { 
      scheduledThreadPoolExecutor = null; 
      this.immediateService = Executors.newSingleThreadExecutor(new ThreadFactoryBuilder(). 
       setNameFormat(RunOnShutdownScheduledExecutorService.class.getName() + "-%d").build()); 
     } 
    } 

    @Override 
    public boolean isShutdown() 
    { 
     return delegate.isShutdown(); 
    } 

    @Override 
    public boolean isTerminated() 
    { 
     return delegate.isTerminated(); 
    } 

    @Override 
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException 
    { 
     long before = System.nanoTime(); 
     if (!delegate.awaitTermination(timeout, unit)) 
      return false; 
     long after = System.nanoTime(); 
     long timeLeft = timeout - unit.convert(after - before, TimeUnit.NANOSECONDS); 
     return immediateService.awaitTermination(timeLeft, unit); 
    } 

    @Override 
    public void execute(Runnable command) 
    { 
     delegate.execute(command); 
    } 

    @Override 
    public ScheduledFuture<?> schedule(final Runnable command, long delay, TimeUnit unit) 
    { 
     CleaningRunnable decorated = new CleaningRunnable(command); 
     ScheduledFuture<?> future = delegate.schedule(decorated, delay, unit); 
     decorated.setFuture(future); 
     tasks.put(future, Executors.callable(command)); 
     return new CleaningScheduledFuture<>(future); 
    } 

    @Override 
    public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) 
    { 
     CallableWithFuture<V> decorated = new CallableWithFuture<>(callable); 
     ScheduledFuture<V> future = delegate.schedule(decorated, delay, unit); 
     decorated.setFuture(future); 
     tasks.put(future, callable); 
     return new CleaningScheduledFuture<>(future); 
    } 

    @Override 
    public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, 
     TimeUnit unit) 
    { 
     CleaningRunnable decorated = new CleaningRunnable(command); 
     ScheduledFuture<?> future = delegate.scheduleAtFixedRate(decorated, initialDelay, period, unit); 
     decorated.setFuture(future); 
     tasks.put(future, Executors.callable(command)); 
     return new CleaningScheduledFuture<>(future); 
    } 

    @Override 
    public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, 
     TimeUnit unit) 
    { 
     CleaningRunnable decorated = new CleaningRunnable(command); 
     ScheduledFuture<?> future = 
      delegate.scheduleWithFixedDelay(decorated, initialDelay, delay, unit); 
     decorated.setFuture(future); 
     tasks.put(future, Executors.callable(command)); 
     return new CleaningScheduledFuture<>(future); 
    } 

    @Override 
    public synchronized void shutdown() 
    { 
     if (delegate.isShutdown()) 
      return; 
     if (scheduledThreadPoolExecutor != null) 
     { 
      // WORKAROUND: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7069418 
      // 
      // Cancel waiting scheduled tasks, otherwise executor won't shut down 
      scheduledThreadPoolExecutor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false); 
     } 
     delegate.shutdown(); 
     // Users will not be able to cancel() Futures past this point so we're guaranteed that 
     // "tasks" will not be modified. 

     final List<Callable<?>> outstandingTasks = Lists.newArrayList(); 
     for (Map.Entry<Future<?>, Callable<?>> entry: tasks.entrySet()) 
     { 
      Future<?> future = entry.getKey(); 
      Callable<?> task = entry.getValue(); 

      if (future.isDone() && future.isCancelled()) 
      { 
       // Task called by the underlying executor, not the user. See CleaningScheduledFuture. 
       outstandingTasks.add(task); 
      } 
     } 
     tasks.clear(); 
     if (outstandingTasks.isEmpty()) 
     { 
      immediateService.shutdown(); 
      return; 
     } 

     immediateService.submit(new Callable<Void>() 
     { 
      @Override 
      public Void call() throws Exception 
      { 
       delegate.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS); 

       // Execute outstanding tasks only after the delegate executor finishes shutting down 
       for (Callable<?> task: outstandingTasks) 
        immediateService.submit(task); 
       immediateService.shutdown(); 
       return null; 
      } 
     }); 
    } 

    @Override 
    public List<Runnable> shutdownNow() 
    { 
     return delegate.shutdownNow(); 
    } 

    /** 
    * A Runnable that removes its future when running. 
    */ 
    private class CleaningRunnable implements Runnable 
    { 
     private final Runnable delegate; 
     private Future<?> future; 

     /** 
     * Creates a new RunnableWithFuture. 
     * 
     * @param delegate the Runnable to delegate to 
     * @throws NullPointerException if delegate is null 
     */ 
     public CleaningRunnable(Runnable delegate) 
     { 
      Preconditions.checkNotNull(delegate, "delegate may not be null"); 

      this.delegate = delegate; 
     } 

     /** 
     * Associates a Future with the runnable. 
     * 
     * @param future a future 
     */ 
     public void setFuture(Future<?> future) 
     { 
      this.future = future; 
     } 

     @Override 
     public void run() 
     { 
      tasks.remove(future); 
      delegate.run(); 
     } 
    } 

    /** 
    * A Callable that removes its future when running. 
    */ 
    private class CallableWithFuture<V> implements Callable<V> 
    { 
     private final Callable<V> delegate; 
     private Future<V> future; 

     /** 
     * Creates a new CallableWithFuture. 
     * 
     * @param delegate the Callable to delegate to 
     * @throws NullPointerException if delegate is null 
     */ 
     public CallableWithFuture(Callable<V> delegate) 
     { 
      Preconditions.checkNotNull(delegate, "delegate may not be null"); 

      this.delegate = delegate; 
     } 

     /** 
     * Associates a Future with the runnable. 
     * 
     * @param future a future 
     */ 
     public void setFuture(Future<V> future) 
     { 
      this.future = future; 
     } 

     @Override 
     public V call() throws Exception 
     { 
      tasks.remove(future); 
      return delegate.call(); 
     } 
    } 

    /** 
    * A ScheduledFuture that removes its future when canceling. 
    * 
    * This allows us to differentiate between tasks canceled by the user and the underlying 
    * executor. Tasks canceled by the user are removed from "tasks". 
    * 
    * @param <V> The result type returned by this Future 
    */ 
    private class CleaningScheduledFuture<V> implements ScheduledFuture<V> 
    { 
     private final ScheduledFuture<V> delegate; 

     /** 
     * Creates a new MyScheduledFuture. 
     * 
     * @param delegate the future to delegate to 
     * @throws NullPointerException if delegate is null 
     */ 
     public CleaningScheduledFuture(ScheduledFuture<V> delegate) 
     { 
      Preconditions.checkNotNull(delegate, "delegate may not be null"); 

      this.delegate = delegate; 
     } 

     @Override 
     public long getDelay(TimeUnit unit) 
     { 
      return delegate.getDelay(unit); 
     } 

     @Override 
     public int compareTo(Delayed o) 
     { 
      return delegate.compareTo(o); 
     } 

     @Override 
     public boolean cancel(boolean mayInterruptIfRunning) 
     { 
      boolean result = delegate.cancel(mayInterruptIfRunning); 

      if (result) 
      { 
       // Tasks canceled by users are removed from "tasks" 
       tasks.remove(delegate); 
      } 
      return result; 
     } 

     @Override 
     public boolean isCancelled() 
     { 
      return delegate.isCancelled(); 
     } 

     @Override 
     public boolean isDone() 
     { 
      return delegate.isDone(); 
     } 

     @Override 
     public V get() throws InterruptedException, ExecutionException 
     { 
      return delegate.get(); 
     } 

     @Override 
     public V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, 
      TimeoutException 
     { 
      return delegate.get(timeout, unit); 
     } 
    } 
} 

Answer 2

Świetne pytanie! Wygląda na to, że możesz sam rozwiązać problem.

Jedną opcją może być owinięcie ScheduledThreadPoolExecutor za pomocą własnej implementacji ScheduledExecutorService. Kiedy przychodzi czas na zamknięcie usługi, anuluj wszelkie zadania, które można anulować, a zamiast tego wyślij je do serwisu, który wykona je natychmiast. Następnie ta usługa.

Oto bardzo nieokreślony kod, który pokazuje, co mam na myśli, chociaż ostrzegam, że mogą tu występować pułapki, ponieważ zostały porozbijane w ciągu kilku minut. W szczególności nie dołożyłem dużego wysiłku, aby zapewnić bezpieczeństwo wątków.

class RunOnShutdownScheduledExecutorService extends AbstractExecutorService implements ScheduledExecutorService { 
    private final ScheduledExecutorService delegateService; 

    private Map<Future<?>, Runnable> scheduledFutures = 
      Collections.synchronizedMap(new IdentityHashMap<Future<?>, Runnable>()); 


    public RunOnShutdownScheduledExecutorService(ScheduledExecutorService delegateService) { 
     this.delegateService = delegateService; 
    } 

    public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) { 
     ScheduledFuture<?> future = delegateService.schedule(command, delay, unit); 
     scheduledFutures.put(future, command); 
     return future; 
    } 

    public void shutdown() { 
     delegateService.shutdown(); 
     ExecutorService immediateService = Executors.newFixedThreadPool(5); 
     for (Map.Entry<Future<?>, Runnable> entry : scheduledFutures.entrySet()) { 
      Future<?> future = entry.getKey(); 
      Runnable task = entry.getValue(); 
      if (!future.isDone()) { 
       if (future.cancel(false)) { 
        immediateService.submit(task); 
       } 
      } 
     } 
     immediateService.shutdown(); 
    } 

    //... 
}