org.jboss.cache.eviction
Class BaseEvictionAlgorithm

java.lang.Object
  org.jboss.cache.eviction.BaseEvictionAlgorithm

All Implemented Interfaces:

EvictionAlgorithm

Direct Known Subclasses:

BaseSortedEvictionAlgorithm, FIFOAlgorithm, LRUAlgorithm, MRUAlgorithm

public abstract class BaseEvictionAlgorithm
extends java.lang.Object
implements EvictionAlgorithm

Abstract Event Processing Eviction Algorithm. This class is used to implement basic event processing for Eviction Algorithms. To extend this abstract class to make an Eviction Algorithm, implement the abstract methods and a policy.

Version:

$Revision: 1.4 $

Author:

Daniel Huang - dhuang@jboss.org 10/2005

Field Summary

protected EvictionQueue	evictionQueue
protected EDU.oswego.cs.dl.util.concurrent.BoundedBuffer	recycleQueue
protected Region	region

Constructor Summary

protected

BaseEvictionAlgorithm()

Method Summary

protected void	emptyRecycleQueue() Empty the Recycle Queue.
protected void	evict(NodeEntry ne)
protected boolean	evictCacheNode(Fqn fqn) Evict a node from cache.
EvictionQueue	getEvictionQueue() Get the underlying EvictionQueue implementation.
protected void	initialize(Region region)
void	process(Region region) Process the given region.
protected void	processAddedNodes(Fqn fqn) Process an Added cache node.
protected void	processQueues(Region region) Event processing for Evict/Add/Visiting of nodes.
protected void	processRemovedNodes(Fqn fqn) Remove a node from cache.
protected void	processVisitedNodes(Fqn fqn) Visit a node in cache.
protected void	prune()
void	resetEvictionQueue(Region region) Reset the whole eviction queue.
protected abstract EvictionQueue	setupEvictionQueue(Region region) This method will create an EvictionQueue implementation and prepare it for use.
protected abstract boolean	shouldEvictNode(NodeEntry ne) This method will check whether the given node should be evicted or not.

Methods inherited from class java.lang.Object

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

Field Detail

region

protected Region region

recycleQueue

protected EDU.oswego.cs.dl.util.concurrent.BoundedBuffer recycleQueue

evictionQueue

protected EvictionQueue evictionQueue

Constructor Detail

BaseEvictionAlgorithm

protected BaseEvictionAlgorithm()

Method Detail

setupEvictionQueue

protected abstract EvictionQueue setupEvictionQueue(Region region)
                                             throws EvictionException

This method will create an EvictionQueue implementation and prepare it for use.

Parameters:

region - Region to setup an eviction queue for.

Returns:

The created EvictionQueue to be used as the eviction queue for this algorithm.

Throws:

EvictionException

See Also:

EvictionQueue

shouldEvictNode

protected abstract boolean shouldEvictNode(NodeEntry ne)

This method will check whether the given node should be evicted or not.

Parameters:

ne - NodeEntry to test eviction for.

Returns:

True if the given node should be evicted. False if the given node should not be evicted.

initialize

protected void initialize(Region region)
                   throws EvictionException

Throws:

EvictionException

process

public void process(Region region)
             throws EvictionException

Process the given region.

Eviction Processing encompasses the following:

- Add/Remove/Visit Nodes - Prune according to Eviction Algorithm - Empty/Retry the recycle queue of previously evicted but locked (during actual cache eviction) nodes.

Specified by:

process in interface EvictionAlgorithm

Parameters:

region - Cache region to process for eviction.

Throws:

EvictionException

resetEvictionQueue

public void resetEvictionQueue(Region region)

Description copied from interface: EvictionAlgorithm

Reset the whole eviction queue. Queue may needs to be reset due to corrupted state, for example.

Specified by:

resetEvictionQueue in interface EvictionAlgorithm

Parameters:

region - Region that this algorithm will operate on.

getEvictionQueue

public EvictionQueue getEvictionQueue()

Get the underlying EvictionQueue implementation.

Specified by:

getEvictionQueue in interface EvictionAlgorithm

Returns:

the EvictionQueue used by this algorithm

See Also:

EvictionQueue

processQueues

protected void processQueues(Region region)
                      throws EvictionException

Event processing for Evict/Add/Visiting of nodes.

- On AddEvents a new element is added into the eviction queue - On RemoveEvents, the removed element is removed from the eviction queue. - On VisitEvents, the visited node has its eviction statistics updated (idleTime, numberOfNodeVisists, etc..)

Parameters:

region - Cache region to process for eviction.

Throws:

EvictionException

evict

protected void evict(NodeEntry ne)

evictCacheNode

protected boolean evictCacheNode(Fqn fqn)

Evict a node from cache.

Parameters:

fqn - node corresponds to this fqn

Returns:

True if successful

processAddedNodes

protected void processAddedNodes(Fqn fqn)
                          throws EvictionException

Process an Added cache node.

Parameters:

fqn - FQN of the added node.

Throws:

EvictionException

processRemovedNodes

protected void processRemovedNodes(Fqn fqn)
                            throws EvictionException

Remove a node from cache.

This method will remove the node from the eviction queue as well as evict the node from cache.

If a node cannot be removed from cache, this method will remove it from the eviction queue and place the element into the recycleQueue. Each node in the recycle queue will get retried until proper cache eviction has taken place.

Because EvictionQueues are collections, when iterating them from an iterator, use iterator.remove() to avoid ConcurrentModificationExceptions. Use the boolean parameter to indicate the calling context.

Parameters:

fqn - FQN of the removed node

Throws:

EvictionException

processVisitedNodes

protected void processVisitedNodes(Fqn fqn)
                            throws EvictionException

Visit a node in cache.

This method will update the numVisits and modifiedTimestamp properties of the Node. These properties are used as statistics to determine eviction (LRU, LFU, MRU, etc..)

*Note* that this method updates Node Entries by reference and does not put them back into the queue. For some sorted collections, a remove, and a re-add is required to maintain the sorted order of the elements.

Parameters:

fqn - FQN of the visited node.

Throws:

EvictionException

emptyRecycleQueue

protected void emptyRecycleQueue()
                          throws EvictionException

Empty the Recycle Queue.

This method will go through the recycle queue and retry to evict the nodes from cache.

Throws:

EvictionException

prune

protected void prune()
              throws EvictionException

Throws:

EvictionException