org.aredis.util.concurrent

Class SingleConsumerQueue<E>

java.lang.Object

org.aredis.util.concurrent.SingleConsumerQueue<E>

Type Parameters:

E - Type of items in the Q

public class SingleConsumerQueue<E>
extends Object

This is a Wrapper over a LinkedBlockingQueue for use with a Single Consumer. This is used by the internal request and response Q's of AsyncRedisConnection. The Consumer Thread can optionally quit on an empty Q in which case the Q is marked as IDLE. The writer has an option to acquire the Q if it is IDLE when writing to the head of the Q. If the Q is acquired then then the writer should initiate the listener.

Note: Only One consumer should be receiving for a SingleConsumerQueue. This can be ensured by using add method to acquire an idle consumer status and initiate the consumer and the remove method to set back the consumer status to idle and quit the consumer thread in case of an empty Q.

Author:

Suresh

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	SingleConsumerQueue.IdleListener<E> Callback Interface to get called back when the IDLE status of the Q changes.
static class	SingleConsumerQueue.QueueStatus

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_ENQUE_TIME_MILLIS Default value of maxEnqueTimeMillis.

Constructor Summary

Constructors

Constructor and Description
SingleConsumerQueue() Creates a Q with unbounded capacity.
SingleConsumerQueue(int pcapacity) Creates a Q with the given capacity and default maxEnqueTimeMillis of 5 seconds
SingleConsumerQueue(int pcapacity, long pmaxEnqueTimeMillis) Creates a Q with the given capacity and maxEnqueTimeMillis to wait for when adding to the Q in case the Q is full.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	acquireIdle() Acquires an idle Q and marks it as active.
boolean	add(E e, boolean acquireIfIdle) Adds an item to the head of the Q.
SingleConsumerQueue.IdleListener<E>	getIdleListener() Gets the idle listener in use.
void	markIdle() Unconditionally mark the Q idle.
void	push(E e) Push to head of Q.
E	remove(long timeoutMicros, boolean releaseIfEmpty) Remove from the tail of the Q.
void	setIdleListener(SingleConsumerQueue.IdleListener<E> pidleListener) Sets an idle listener which is called whenever the Q status changes from IDLE to ACTIVE or vice-versa.
int	size() Gets the size of the Q.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_ENQUE_TIME_MILLIS

public static final int DEFAULT_MAX_ENQUE_TIME_MILLIS

Default value of maxEnqueTimeMillis.

See Also:

Constant Field Values

Constructor Detail

SingleConsumerQueue

public SingleConsumerQueue(int pcapacity,
                   long pmaxEnqueTimeMillis)

Creates a Q with the given capacity and maxEnqueTimeMillis to wait for when adding to the Q in case the Q is full.

Parameters:

pcapacity - Q capacity or 0 for unbounded

pmaxEnqueTimeMillis - Max Milliseconds to wait when adding to Q if the Q is full

SingleConsumerQueue

public SingleConsumerQueue(int pcapacity)

Creates a Q with the given capacity and default maxEnqueTimeMillis of 5 seconds

Parameters:

pcapacity - Q capacity or 0 for unbounded

SingleConsumerQueue

public SingleConsumerQueue()

Creates a Q with unbounded capacity.

Method Detail

add

public boolean add(E e,
          boolean acquireIfIdle)

Adds an item to the head of the Q.

Parameters:

e - item to add

acquireIfIdle - pass true to acquire the Q if currently idle. When used concurrently exactly one of the callers gets the return value as true.

Returns:

true if an idle Q has been acquired and marked active in which case the caller should start the Consumer thread. Always returs false if acquireIfIdle has been passed as false.

remove

public E remove(long timeoutMicros,
       boolean releaseIfEmpty)

Remove from the tail of the Q.

Parameters:

timeoutMicros - Max microseconds to wait for in case the Q is empty

releaseIfEmpty - If true then the Q is marked idle if the Q is empty and this method returns null.

Returns:

Item or null if the Q is empty

push

public void push(E e)

Push to head of Q. Non concurrent method to be used only by consumer.

Parameters:

e - Item

markIdle

public void markIdle()

Unconditionally mark the Q idle. The caller should be holding the Q. Normally there should be a double check after this call to ensure that the idle condition continues to hold which usually is that the Q continues to be empty. If not the processing action should be initiated by trying to acquire back the idle Q.

acquireIdle

public boolean acquireIdle()

Acquires an idle Q and marks it as active.

Returns:

true if the Q is idle and has been acquired by this thread

size

public int size()

Gets the size of the Q.

Returns:

Q size

getIdleListener

public SingleConsumerQueue.IdleListener<E> getIdleListener()

Gets the idle listener in use.

Returns:

The idle listener or null if not set

setIdleListener

public void setIdleListener(SingleConsumerQueue.IdleListener<E> pidleListener)

Sets an idle listener which is called whenever the Q status changes from IDLE to ACTIVE or vice-versa.

Parameters:

pidleListener - Idle listener or null to unset the current listener