org.apache.servicemix.eip.support.resequence

Class ResequencerEngine<E>

java.lang.Object

org.apache.servicemix.eip.support.resequence.ResequencerEngine<E>

All Implemented Interfaces:

TimeoutHandler

public class ResequencerEngine<E>
extends java.lang.Object
implements TimeoutHandler

Resequences elements based on a given SequenceElementComparator. This resequencer is designed for resequencing element streams. Resequenced elements are added to an output Queue. The resequencer is configured via the timeout and capacity properties.

• timeout. Defines the timeout (in milliseconds) for a given element managed by this resequencer. An out-of-sequence element can only be marked as ready-for-delivery if it either times out or if it has an immediate predecessor (in that case it is in-sequence). If an immediate predecessor of a waiting element arrives the timeout task for the waiting element will be cancelled (which marks it as ready-for-delivery).

  If the maximum out-of-sequence time between elements within a stream is known, the timeout value should be set to this value. In this case it is guaranteed that all elements of a stream will be delivered in sequence to the output queue. However, large timeout values might require a very high resequencer capacity which might be in conflict with available memory resources. The lower the timeout value is compared to the out-of-sequence time between elements within a stream the higher the probability is for out-of-sequence elements delivered by this resequencer.

• capacity. The capacity of this resequencer.

Whenever a timeout for a certain element occurs or an element has been added to this resequencer a delivery attempt is started. If a (sub)sequence of elements is ready-for-delivery then they are added to output queue.

The resequencer remembers the last-delivered element. If an element arrives which is the immediate successor of the last-delivered element it will be delivered immediately and the last-delivered element is adjusted accordingly. If the last-delivered element is null i.e. the resequencer was newly created the first arriving element will wait timeout milliseconds for being delivered to the output queue.

Author:

Martin Krasser

Constructor Summary

Constructors

Constructor and Description
ResequencerEngine(SequenceElementComparator<E> comparator) Creates a new resequencer instance with a default timeout of 2000 milliseconds.
ResequencerEngine(SequenceElementComparator<E> comparator, int capacity) Creates a new resequencer instance with a default timeout of 2000 milliseconds.

Method Summary

Methods

Modifier and Type	Method and Description
void	add(E o) Adds an element to this resequencer throwing an exception if the maximum capacity is reached.
java.util.Queue<E>	getOutQueue() Returns the output queue.
long	getTimeout() Returns this resequencer's timeout value.
void	put(E o) Adds an element to this resequencer waiting, if necessary, until capacity becomes available.
void	setOutQueue(java.util.Queue<E> outQueue) Sets the output queue.
void	setTimeout(long timeout) Sets this sequencer's timeout value.
void	stop() Stops this resequencer (i.e.
void	timeout(Timeout timout) Handles a timeout notification by starting a delivery attempt.

Methods inherited from class java.lang.Object

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

Constructor Detail

ResequencerEngine

public ResequencerEngine(SequenceElementComparator<E> comparator)

Creates a new resequencer instance with a default timeout of 2000 milliseconds. The capacity is set to Integer.MAX_VALUE.

Parameters:

comparator - a sequence element comparator.

ResequencerEngine

public ResequencerEngine(SequenceElementComparator<E> comparator,
                 int capacity)

Creates a new resequencer instance with a default timeout of 2000 milliseconds.

Parameters:

comparator - a sequence element comparator.

capacity - the capacity of this resequencer.

Method Detail

stop

public void stop()

Stops this resequencer (i.e. this resequencer's Timer instance).

getOutQueue

public java.util.Queue<E> getOutQueue()

Returns the output queue.

Returns:

the output queue.

setOutQueue

public void setOutQueue(java.util.Queue<E> outQueue)

Sets the output queue.

Parameters:

outQueue - output queue.

getTimeout

public long getTimeout()

Returns this resequencer's timeout value.

Returns:

the timeout in milliseconds.

setTimeout

public void setTimeout(long timeout)

Sets this sequencer's timeout value.

Parameters:

timeout - the timeout in milliseconds.

timeout

public void timeout(Timeout timout)

Handles a timeout notification by starting a delivery attempt.

Specified by:

timeout in interface TimeoutHandler

Parameters:

timout - timeout task that caused the notification.

add

public void add(E o)

Adds an element to this resequencer throwing an exception if the maximum capacity is reached.

Parameters:

o - element to be resequenced.

Throws:

java.lang.IllegalStateException - if the element cannot be added at this time due to capacity restrictions.

put

public void put(E o)
         throws java.lang.InterruptedException

Adds an element to this resequencer waiting, if necessary, until capacity becomes available.

Parameters:

o - element to be resequenced.

Throws:

java.lang.InterruptedException - if interrupted while waiting.