Package org.apache.hadoop.hdfs.server.datanode.checker

Class AbstractFuture<V>

java.lang.Object
org.apache.hadoop.hdfs.server.datanode.checker.AbstractFuture<V>
All Implemented Interfaces:
Future<V>, org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ListenableFuture<V>
@GwtCompatible(emulated=true) public abstract class AbstractFuture<V> extends Object implements org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ListenableFuture<V>
An abstract implementation of ListenableFuture, intended for advanced users only. More common ways to create a ListenableFuture include instantiating a SettableFuture, submitting a task to a ListeningExecutorService, and deriving a Future from an existing one, typically using methods like (ListenableFuture, org.apache.hadoop.thirdparty.com.google.common.base.Function) Futures.transform and its overloaded versions.

This class implements all methods in ListenableFuture. Subclasses should provide a way to set the result of the computation through the protected methods set(Object), setFuture(ListenableFuture) and setException(Throwable). Subclasses may also override interruptTask(), which will be invoked automatically if a call to cancel(true) succeeds in canceling the future. Subclasses should rarely override other methods.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    AbstractFuture()
    Constructor for use by subclasses.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addListener(Runnable listener, Executor executor)
    protected void
    afterDone()
    Callback method that is called exactly once after the future is completed.
    boolean
    cancel(boolean mayInterruptIfRunning)
    static Executor
    directExecutor()
    Returns an Executor that runs each task in the thread that invokes execute, as in ThreadPoolExecutor.CallerRunsPolicy.
    V
    get()
    V
    get(long timeout, TimeUnit unit)
    static <V> V
    getDone(Future<V> future)
     
    protected void
    interruptTask()
    Subclasses can override this method to implement interruption of the future's computation.
    boolean
    isCancelled()
     
    boolean
    isDone()
     
    protected boolean
    set(V value)
    Sets the result of this Future unless this Future has already been cancelled or set (including set asynchronously).
    protected boolean
    setException(Throwable throwable)
    Sets the failed result of this Future unless this Future has already been cancelled or set (including set asynchronously).
    protected boolean
    setFuture(org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ListenableFuture<? extends V> future)
    Sets the result of this Future to match the supplied input Future once the supplied Future is done, unless this Future has already been cancelled or set (including "set asynchronously," defined below).
    protected final boolean
    wasInterrupted()
    Returns true if this future was cancelled with mayInterruptIfRunning set to true.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • AbstractFuture

      protected AbstractFuture()
      Constructor for use by subclasses.

  • Method Details

    • get

      public V get(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException, ExecutionException

      The default AbstractFuture implementation throws InterruptedException if the current thread is interrupted before or during the call, even if the value is already available.

      Specified by:
      get in interface Future<V>
      Throws:
      InterruptedException - if the current thread was interrupted before or during the call (optional but recommended).
      CancellationException
      TimeoutException
      ExecutionException

    • get

      public V get() throws InterruptedException, ExecutionException

      The default AbstractFuture implementation throws InterruptedException if the current thread is interrupted before or during the call, even if the value is already available.

      Specified by:
      get in interface Future<V>
      Throws:
      InterruptedException - if the current thread was interrupted before or during the call (optional but recommended).
      CancellationException
      ExecutionException

    • isDone

      public boolean isDone()
      Specified by:
      isDone in interface Future<V>

    • isCancelled

      public boolean isCancelled()
      Specified by:
      isCancelled in interface Future<V>

    • cancel

      public boolean cancel(boolean mayInterruptIfRunning)

      If a cancellation attempt succeeds on a Future that had previously been set asynchronously, then the cancellation will also be propagated to the delegate Future that was supplied in the setFuture call.

      Specified by:
      cancel in interface Future<V>

    • interruptTask

      protected void interruptTask()
      Subclasses can override this method to implement interruption of the future's computation. The method is invoked automatically by a successful call to cancel(true).

      The default implementation does nothing.

      Since:
      10.0

    • wasInterrupted

      protected final boolean wasInterrupted()
      Returns true if this future was cancelled with mayInterruptIfRunning set to true.
      Since:
      14.0

    • addListener

      public void addListener(Runnable listener, Executor executor)
      Specified by:
      addListener in interface org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ListenableFuture<V>
      Since:
      10.0

    • set

      protected boolean set(@Nullable V value)
      Sets the result of this Future unless this Future has already been cancelled or set (including set asynchronously). When a call to this method returns, the Future is guaranteed to be done only if the call was accepted (in which case it returns true). If it returns false, the Future may have previously been set asynchronously, in which case its result may not be known yet. That result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).
      Parameters:
      value - the value to be used as the result
      Returns:
      true if the attempt was accepted, completing the Future

    • setException

      protected boolean setException(Throwable throwable)
      Sets the failed result of this Future unless this Future has already been cancelled or set (including set asynchronously). When a call to this method returns, the Future is guaranteed to be done only if the call was accepted (in which case it returns true). If it returns false, the Future may have previously been set asynchronously, in which case its result may not be known yet. That result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).
      Parameters:
      throwable - the exception to be used as the failed result
      Returns:
      true if the attempt was accepted, completing the Future

    • setFuture

      @Beta protected boolean setFuture(org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ListenableFuture<? extends V> future)
      Sets the result of this Future to match the supplied input Future once the supplied Future is done, unless this Future has already been cancelled or set (including "set asynchronously," defined below).

      If the supplied future is done when this method is called and the call is accepted, then this future is guaranteed to have been completed with the supplied future by the time this method returns. If the supplied future is not done and the call is accepted, then the future will be set asynchronously. Note that such a result, though not yet known, cannot be overridden by a call to a set* method, only by a call to cancel(boolean).

      If the call setFuture(delegate) is accepted and this Future is later cancelled, cancellation will be propagated to delegate. Additionally, any call to setFuture after any cancellation will propagate cancellation to the supplied Future.

      Parameters:
      future - the future to delegate to
      Returns:
      true if the attempt was accepted, indicating that the Future was not previously cancelled or set.
      Since:
      19.0

    • getDone

      public static <V> V getDone(Future<V> future) throws ExecutionException
      Throws:
      ExecutionException

    • afterDone

      @Beta protected void afterDone()
      Callback method that is called exactly once after the future is completed.

      If interruptTask() is also run during completion, afterDone() runs after it.

      The default implementation of this method in AbstractFuture does nothing. This is intended for very lightweight cleanup work, for example, timing statistics or clearing fields. If your task does anything heavier consider, just using a listener with an executor.

      Since:
      20.0

    • directExecutor

      public static Executor directExecutor()
      Returns an Executor that runs each task in the thread that invokes execute, as in ThreadPoolExecutor.CallerRunsPolicy.

      This instance is equivalent to: 

         
   final class DirectExecutor implements Executor {
     public void execute(Runnable r) {
       r.run();
     }
   }