org.apache.jcs.auxiliary.disk.indexed

Class IndexedDiskCache

java.lang.Object

org.apache.jcs.auxiliary.AbstractAuxiliaryCache

org.apache.jcs.auxiliary.AbstractAuxiliaryCacheEventLogging

org.apache.jcs.auxiliary.disk.AbstractDiskCache

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

All Implemented Interfaces:

java.io.Serializable, AuxiliaryCache, ICache, ICacheType

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.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	IndexedDiskCache.LRUMap Class for recylcing and lru.

Field Summary

Fields

Modifier and Type	Field and Description
protected EDU.oswego.cs.dl.util.concurrent.ReentrantWriterPreferenceReadWriteLock	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 class org.apache.jcs.auxiliary.AbstractAuxiliaryCache

cacheEventLogger, elementSerializer, keyMatcher

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

CACHE_HUB, DISK_CACHE, LATERAL_CACHE, REMOTE_CACHE

Constructor Summary

Constructors

Constructor and Description
IndexedDiskCache(IndexedDiskCacheAttributes cattr) Constructor for the DiskCache object.

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	checkForDedOverlaps(IndexedDiskElementDescriptor[] sortedDescriptors) Detects any overlapping elements.
void	dump() For debugging.
void	dump(boolean dumpValues) For debugging.
AuxiliaryCacheAttributes	getAuxiliaryCacheAttributes() This returns the generic attributes for an auxiliary cache.
protected long	getBytesFree() Returns the number of bytes that are free.
protected long	getDataFileSize() This is for debugging and testing.
protected java.lang.String	getDiskLocation() This is used by the event logging.
java.util.Set	getGroupKeys(java.lang.String groupName) Gets the group keys from the disk.
protected int	getRecyleBinSize() Returns the size of the recyclebin in number of elements.
protected int	getRecyleCount() Returns the number of times we have used spots from the recycle bin.
int	getSize() Returns the current cache size.
IStats	getStatistics() Returns info about the disk cache.
java.lang.String	getStats() Gets basic stats for the disk cache.
protected int	getTimesOptimized() This is exposed for testing.
protected void	loadKeys() Loads the keys from the .key file.
protected void	optimizeFile() File optimization is handled by this method.
void	processDispose() Dispose of the disk cache in a background thread.
protected ICacheElement	processGet(java.io.Serializable key) Gets the key, then goes to disk to get the object.
java.util.Map	processGetMatching(java.lang.String pattern) Gets matching items from the cache.
protected boolean	processRemove(java.io.Serializable key) Returns true if the removal was successful; or false if there is nothing to remove.
void	processRemoveAll() Remove all the items from the disk cache by reseting everything.
protected void	processUpdate(ICacheElement ce) Update the disk cache.
protected void	saveKeys() Saves key file to disk.

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

dispose, doDispose, doGet, doGetMatching, doRemove, doRemoveAll, doUpdate, get, getCacheName, getCacheType, getEventLoggingExtraInfo, getMatching, getStatus, processGetMultiple, remove, removeAll, update

Methods inherited from class org.apache.jcs.auxiliary.AbstractAuxiliaryCacheEventLogging

disposeWithEventLogging, getMatchingWithEventLogging, getMultiple, getMultipleWithEventLogging, getWithEventLogging, removeAllWithEventLogging, removeWithEventLogging, updateWithEventLogging

Methods inherited from class org.apache.jcs.auxiliary.AbstractAuxiliaryCache

createICacheEvent, createICacheEvent, getCacheEventLogger, getElementSerializer, getKeyMatcher, logApplicationEvent, logError, logICacheEvent, setCacheEventLogger, setElementSerializer, setKeyMatcher

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.jcs.auxiliary.AuxiliaryCache

setCacheEventLogger, setElementSerializer

Methods inherited from interface org.apache.jcs.engine.behavior.ICache

getMultiple, setKeyMatcher

Field Detail

storageLock

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

checkForDedOverlaps

protected boolean checkForDedOverlaps(IndexedDiskElementDescriptor[] sortedDescriptors)

Detects any overlapping elements. This expects a sorted list.

The total length of an item is IndexedDisk.RECORD_HEADER + ded.len.

Parameters:

sortedDescriptors -

Returns:

false if there are overlaps.

saveKeys

protected void saveKeys()

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

processUpdate

protected void processUpdate(ICacheElement ce)

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

Specified by:

processUpdate in class AbstractAuxiliaryCacheEventLogging

Parameters:

ce - The ICacheElement to put to disk.

processGet

protected ICacheElement processGet(java.io.Serializable key)

Gets the key, then goes to disk to get the object.

Specified by:

processGet in class AbstractAuxiliaryCacheEventLogging

Parameters:

key -

Returns:

ICacheElement or null

See Also:

AbstractDiskCache.doGet(java.io.Serializable)

processGetMatching

public java.util.Map processGetMatching(java.lang.String pattern)

Gets matching items from the cache.

Specified by:

processGetMatching in class AbstractAuxiliaryCacheEventLogging

Parameters:

pattern -

Returns:

a map of Serializable key to ICacheElement element, or an empty map if there is no data in cache matching keys

getGroupKeys

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

Gets the group keys from the disk.

Specified by:

getGroupKeys in interface AuxiliaryCache

Specified by:

getGroupKeys in class AbstractDiskCache

Returns:

a set of group keys

See Also:

AuxiliaryCache.getGroupKeys(java.lang.String)

processRemove

protected boolean processRemove(java.io.Serializable key)

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

Specified by:

processRemove in class AbstractAuxiliaryCacheEventLogging

Parameters:

key -

Returns:

true if at least one item was removed.

processRemoveAll

public void processRemoveAll()

Remove all the items from the disk cache by reseting everything.

Specified by:

processRemoveAll in class AbstractAuxiliaryCacheEventLogging

processDispose

public void processDispose()

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

TODO make dispose window configurable.

Specified by:

processDispose in class AbstractAuxiliaryCacheEventLogging

optimizeFile

protected void optimizeFile()

File optimization is handled by this method. It works as follows:

1. Shutdown recycling and turn on queuing of puts.
2. Take a snapshot of the current descriptors. If there are any removes, ignore them, as they will be compacted during the next optimization.
3. Optimize the snapshot. For each descriptor:
   1. Obtain the write-lock.
   2. Shift the element on the disk, in order to compact out the free space.
   3. Release the write-lock. This allows elements to still be accessible during optimization.
4. Obtain the write-lock.
5. All queued puts are made at the end of the file. Optimize these under a single write-lock.
6. Truncate the file.
7. Release the write-lock.
8. Restore system to standard operation.

getSize

public int getSize()

Returns the current cache size.

Specified by:

getSize in interface ICache

Specified by:

getSize in class AbstractDiskCache

Returns:

The size value

See Also:

ICache.getSize()

getRecyleBinSize

protected int getRecyleBinSize()

Returns the size of the recyclebin in number of elements.

Returns:

The number of items in the bin.

getRecyleCount

protected int getRecyleCount()

Returns the number of times we have used spots from the recycle bin.

Returns:

The number of spots used.

getBytesFree

protected long getBytesFree()

Returns the number of bytes that are free. When an item is removed, its length is recorded. When a spot is used form the recycle bin, the length of the item stored is recorded.

Returns:

The number bytes free on the disk file.

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. This dumps the values by defualt.

dump

public void dump(boolean dumpValues)

For debugging.

Parameters:

dumpValues - A boolean indicating if values should be dumped.

getAuxiliaryCacheAttributes

public AuxiliaryCacheAttributes getAuxiliaryCacheAttributes()

Description copied from interface: AuxiliaryCache

This returns the generic attributes for an auxiliary cache. Most implementations will cast this to a more specific type.

Returns:

Returns the AuxiliaryCacheAttributes.

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()

Returns info about the disk cache.

(non-Javadoc)

Specified by:

getStatistics in interface AuxiliaryCache

Overrides:

getStatistics in class AbstractDiskCache

Returns:

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

See Also:

AuxiliaryCache.getStatistics()

getTimesOptimized

protected int getTimesOptimized()

This is exposed for testing.

Returns:

Returns the timesOptimized.

getDiskLocation

protected java.lang.String getDiskLocation()

This is used by the event logging.

Specified by:

getDiskLocation in class AbstractDiskCache

Returns:

the location of the disk, either path or ip.