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org.apache.lens.server.api.events
Class AsyncEventListener<T extends LensEvent>

java.lang.Object
  org.apache.lens.server.api.events.AsyncEventListener<T>

Type Parameters:

T - the generic type

All Implemented Interfaces:

LensEventListener<T>

Direct Known Subclasses:

MetricsServiceImpl.AsyncQueryStatusListener, QueryEndNotifier, QueryExecutionStatisticsGenerator, ResultFormatter, StatisticsLogPartitionHandler, StatisticsStore

public abstract class AsyncEventListener<T extends LensEvent>
extends Object
implements LensEventListener<T>

Event listeners should implement this class if they wish to process events asynchronously. This should be used when event processing can block, or is computationally intensive.

Field Summary

Fields inherited from interface org.apache.lens.server.api.events.LensEventListener

HANDLER_METHOD_NAME

Constructor Summary

AsyncEventListener()
Create a single threaded event listener with an unbounded queue, with daemon threads.

AsyncEventListener(int poolSize)
Create a event listener with poolSize threads with an unbounded queue and daemon threads.

AsyncEventListener(int poolSize, int maxQueueSize, long timeOutSeconds, boolean isDaemon)
Create an asynchronous event listener which uses a thread poool to process events.

Method Summary

BlockingQueue<Runnable>	getEventQueue()
void	onEvent(T event) Creates a new runnable and calls the process method in it.
abstract void	process(T event) Should implement the actual event handling.
void	stop() Should be called to stop the event processor thread.

Methods inherited from class java.lang.Object

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

Constructor Detail

AsyncEventListener

public AsyncEventListener()

Create a single threaded event listener with an unbounded queue, with daemon threads.

AsyncEventListener

public AsyncEventListener(int poolSize)

Create a event listener with poolSize threads with an unbounded queue and daemon threads.

Parameters:

poolSize - the pool size

AsyncEventListener

public AsyncEventListener(int poolSize,
                          int maxQueueSize,
                          long timeOutSeconds,
                          boolean isDaemon)

Create an asynchronous event listener which uses a thread poool to process events.

Parameters:

poolSize - size of the event processing pool

maxQueueSize - max size of the event queue, if this is non positive, then the queue is unbounded

timeOutSeconds - time out in seconds when an idle thread is destroyed

isDaemon - if the threads used to process should be daemon threads, if false, then implementation should call stop() to stop the thread pool

Method Detail

onEvent

public void onEvent(T event)
             throws LensException

Creates a new runnable and calls the process method in it.

Specified by:

onEvent in interface LensEventListener<T extends LensEvent>

Parameters:

event - the event

Throws:

LensException - the lens exception

process

public abstract void process(T event)

Should implement the actual event handling.

Parameters:

event - the event

stop

public void stop()

Should be called to stop the event processor thread.

getEventQueue

public BlockingQueue<Runnable> getEventQueue()