org.apache.jcs.auxiliary.disk.indexed
Class IndexedDiskCache

java.lang.Object
  org.apache.jcs.auxiliary.disk.AbstractDiskCache
      org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCache

All Implemented Interfaces:

AuxiliaryCache, ICache, ICacheType, java.io.Serializable

public class IndexedDiskCache

extends AbstractDiskCache

Disk cache that uses a RandomAccessFile with keys stored in memory. The maximum number of keys stored in memory is configurable. The disk cache tries to recycle spots on disk to limit file expansion.

Version:

$Id: IndexedDiskCache.java 378115 2006-02-15 23:07:30Z asmuts $

See Also:

Serialized Form

Nested Class Summary

class

IndexedDiskCache.LRUMap class for recylcing and lru

Field Summary

protected EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock

storageLock use this lock to synchronize reads and writes to the underlying storage mechansism.

Fields inherited from class org.apache.jcs.auxiliary.disk.AbstractDiskCache

alive, cacheEventQueue, cacheName, purgatory, purgHits

Fields inherited from interface org.apache.jcs.engine.behavior.ICacheType

CACHE_HUB, DISK_CACHE, LATERAL_CACHE, REMOTE_CACHE

Constructor Summary

IndexedDiskCache(IndexedDiskCacheAttributes cattr)
Constructor for the DiskCache object

Method Summary

void	doDispose() Dispose of the disk cache in a background thread.
protected ICacheElement	doGet(java.io.Serializable key) Get a value from the persistent store.
void	doOptimizeRealTime() Dispose of the disk cache in a background thread.
boolean	doRemove(java.io.Serializable key) Returns true if the removal was succesful; or false if there is nothing to remove.
void	doRemoveAll() Remove all the items fromt he disk cache by reseting everything.
void	doUpdate(ICacheElement ce) Update the disk cache.
void	dump() For debugging.
protected long	getDataFileSize() This is for debugging and testing.
java.util.Set	getGroupKeys(java.lang.String groupName) Gets the set of keys of objects currently in the group
int	getSize() Returns the current cache size.
IStats	getStatistics() Returns the historical and statistical data for a region's auxiliary cache.
java.lang.String	getStats() Gets basic stats for the disk cache.
protected void	loadKeys() Loads the keys from the .key file.
protected void	optimizeFile() Note: synchronization currently must be managed by the caller method-- dispose.
protected void	optimizeRealTime() Realtime optimization is handled by this method.
protected void	saveKeys() Saves key file to disk.

Methods inherited from class org.apache.jcs.auxiliary.disk.AbstractDiskCache

dispose, get, getCacheName, getCacheType, getStatus, remove, removeAll, update

Methods inherited from class java.lang.Object

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

Field Detail

storageLock

protected EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock storageLock

use this lock to synchronize reads and writes to the underlying storage mechansism.

Constructor Detail

IndexedDiskCache

public IndexedDiskCache(IndexedDiskCacheAttributes cattr)

Constructor for the DiskCache object

Parameters:

cattr -

Method Detail

loadKeys

protected void loadKeys()
                 throws java.lang.InterruptedException

Loads the keys from the .key file. The keys are stored in a HashMap on disk. This is converted into a LRUMap.

Throws:

java.lang.InterruptedException

saveKeys

protected void saveKeys()

Saves key file to disk. This converts the LRUMap to a HashMap for deserialzation.

doUpdate

public void doUpdate(ICacheElement ce)

Update the disk cache. Called from the Queue. Makes sure the Item has not been retireved from purgatory while in queue for disk. Remove items from purgatory when they go to disk.

Specified by:

doUpdate in class AbstractDiskCache

Parameters:

ce -

doGet

protected ICacheElement doGet(java.io.Serializable key)

Description copied from class: AbstractDiskCache

Get a value from the persistent store.

Specified by:

doGet in class AbstractDiskCache

Parameters:

key -

Returns:

ICacheElement or null

See Also:

AbstractDiskCache.doGet(java.io.Serializable)

getGroupKeys

public java.util.Set getGroupKeys(java.lang.String groupName)

Description copied from interface: AuxiliaryCache

Gets the set of keys of objects currently in the group

Specified by:

getGroupKeys in interface AuxiliaryCache

Specified by:

getGroupKeys in class AbstractDiskCache

doRemove

public boolean doRemove(java.io.Serializable key)

Returns true if the removal was succesful; or false if there is nothing to remove. Current implementation always result in a disk orphan.

Specified by:

doRemove in class AbstractDiskCache

Parameters:

key -

Returns:

doRemoveAll

public void doRemoveAll()

Remove all the items fromt he disk cache by reseting everything.

Specified by:

doRemoveAll in class AbstractDiskCache

doDispose

public void doDispose()

Dispose of the disk cache in a background thread. Joins against this thread to put a cap on the disposal time.

Specified by:

doDispose in class AbstractDiskCache

doOptimizeRealTime

public void doOptimizeRealTime()

Dispose of the disk cache in a background thread. Joins against this thread to put a cap on the disposal time.

optimizeRealTime

protected void optimizeRealTime()

Realtime optimization is handled by this method. It works in this way:

• 1. Lock the active file, create a new file.
• 2. Copy the keys for iteration.
• 3. For each key in the copy, make sure it is still in the active keyhash to prevent putting items on disk that have been removed. It also checks the new keyHash to make sure that a newer version hasn't already been put.
• 4. Write the element for the key copy to disk in the normal proceedure.
• 5. All gets will be serviced by the new file.
• 6. All puts are made on the new file.

optimizeFile

protected void optimizeFile()

Note: synchronization currently must be managed by the caller method-- dispose.

getSize

public int getSize()

Returns the current cache size.

Specified by:

getSize in interface AuxiliaryCache

Specified by:

getSize in class AbstractDiskCache

Returns:

The size value

See Also:

ICache.getSize()

getDataFileSize

protected long getDataFileSize()
                        throws java.io.IOException

This is for debugging and testing.

Returns:

the length of the data file.

Throws:

java.io.IOException

dump

public void dump()

For debugging.

getStats

public java.lang.String getStats()

Gets basic stats for the disk cache.

Specified by:

getStats in interface ICache

Overrides:

getStats in class AbstractDiskCache

Returns:

String

getStatistics

public IStats getStatistics()

Description copied from interface: AuxiliaryCache

Returns the historical and statistical data for a region's auxiliary cache.

Specified by:

getStatistics in interface AuxiliaryCache

Overrides:

getStatistics in class AbstractDiskCache