org.apache.ambari.server.controller.utilities

Class BufferedThreadPoolExecutorCompletionService<V>

java.lang.Object

java.util.concurrent.ExecutorCompletionService<V>

org.apache.ambari.server.controller.utilities.BufferedThreadPoolExecutorCompletionService<V>

Type Parameters:

V -

All Implemented Interfaces:

CompletionService<V>

public class BufferedThreadPoolExecutorCompletionService<V>
extends ExecutorCompletionService<V>

An ExecutorCompletionService which takes a ThreadPoolExecutor and uses its thread pool to execute tasks - buffering any tasks that overflow. Such buffered tasks are later re-submitted to the executor when finished tasks are polled or taken.

This class overrides the ThreadPoolExecutor's RejectedExecutionHandler to collect overflowing tasks. When poll(long, TimeUnit) is invoked, this class will attempt to re-submit any overflow tasks before waiting the specified amount of time. This will prevent blocking on an empty completion queue since the parent ExecutorCompletionService doesn't have any idea that there are tasks waiting to be resubmitted.

The ScalingThreadPoolExecutor can be used in conjunction with this class to provide an efficient buffered, scaling thread pool implementation.

Constructor Summary

Constructors

Constructor and Description
BufferedThreadPoolExecutorCompletionService(ThreadPoolExecutor executor)

Method Summary

Modifier and Type	Method and Description
Future<V>	poll()
Future<V>	poll(long timeout, TimeUnit unit) The goal of this method is to prevent blocking if there are tasks waiting in the overflow queue.
Future<V>	take()

Methods inherited from class java.util.concurrent.ExecutorCompletionService

submit, submit

Methods inherited from class java.lang.Object

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

Constructor Detail

BufferedThreadPoolExecutorCompletionService

public BufferedThreadPoolExecutorCompletionService(ThreadPoolExecutor executor)

Method Detail

take

public Future<V> take()
               throws InterruptedException

Specified by:

take in interface CompletionService<V>

Overrides:

take in class ExecutorCompletionService<V>

Throws:

InterruptedException

poll

public Future<V> poll()

Specified by:

poll in interface CompletionService<V>

Overrides:

poll in class ExecutorCompletionService<V>

poll

public Future<V> poll(long timeout,
                      TimeUnit unit)
               throws InterruptedException

The goal of this method is to prevent blocking if there are tasks waiting in the overflow queue. In the event that the overflow queue was populated, we should not blindly wait on the parent ExecutorCompletionService.poll(long, TimeUnit) method. Instead, we should ensure that we have submitted at least one of our own tasks for completion.

Specified by:

poll in interface CompletionService<V>

Overrides:

poll in class ExecutorCompletionService<V>

Throws:

InterruptedException