org.w3c.www.protocol.http.cache
Class CacheStore

java.lang.Object
  org.w3c.www.protocol.http.cache.CacheStore

All Implemented Interfaces:

PropertyMonitoring

public class CacheStore
extends java.lang.Object
implements PropertyMonitoring

Field Summary

static java.lang.String	CACHE_DIRECTORY_P Name of the property giving the cache's directory.
static java.lang.String	FILE_SIZE_RATIO_P Name of the property indicating the max size for files to be cached.
static java.lang.String	GARBAGE_COLLECTION_ENABLED_P Name of the property enabling garbage collection of the cache.
static java.lang.String	GARBAGE_COLLECTION_THRESHOLD_P Name of the property used to knkow the percentage of bytes to be kept after a garbage collection It defaults to 0.80 (80% of the cache size)
static java.lang.String	GENERATION_COMPACT_DELAY_P Name of the property indicating the amount of time in second between two attempts to compact generations.
static java.lang.String	GENERATION_FILENAME
static java.lang.String	MAX_CACHED_RESOURCES_P Name of the property indicating the maximal number of resources the cache can load in memory (not the content of the resources)
static java.lang.String	MAX_GENERATIONS_P Name of the property indicating the maximal number of generations in this cache store
protected ObservableProperties	props The properties we initialized ourself from.
static java.lang.String	STORE_SIZE_P The name of the properties indicating the storesize of the cache (in bytes).
static java.lang.String	SYNCHRONIZATION_DELAY_P Name of the property indicating the amount of time in second between two synchronization of the database (aka dump on disk) Milliseconds

Constructor Summary

CacheStore()

Method Summary

protected CacheGeneration	addNewGeneration() Create and add a new Generation.
protected void	checkDirs() Check the subdirectories.
protected void	checkState() used for debugging, display some internal information about the state of the cache
protected int	cleanCacheDir() Clean the Cache directory, remove unused files.
protected void	compactGenerations() Compact our generations The algorithm is the following, If the number of generation is the maximum number allowed, then a check is done from the the generation after the MRU one and if the sum of two generation can fit into one, it is done, and the generation is removed from the list
long	getCachedByteCount() get the cached size of this cache
long	getCachedByteFree() get the number of bytes available for the cache memory
CachedResource	getCachedResource(CachedResource cr) extract a cached resource from the store
CachedResource	getCachedResource(java.lang.String url) Get a cached resource relative to the given URL.
CachedResource	getCachedResourceReference(java.lang.String url) Get a cached resource relative to the given URL.
long	getCompactGenerationDelay() Get the delay between two attempts to compact the generations.
CacheGeneration	getLRUGeneration() Get the LRU generation, ie the Least recently used generation
CacheGeneration	getLRULoadedGeneration() Get the oldest loaded generation
CacheGeneration	getMRUGeneration() Get the last generation, ie the Most recently used generation
float	getMRUGenerationRatio() Get the fill ratio of the last generation (the most recently used)
protected java.io.File	getNewEntryFile() allocate a new name for the next cached resource.
CacheGeneration	getNextGeneration(CacheGeneration gen) Get the next generation (in LRU order).
CacheGeneration	getPrevGeneration(CacheGeneration gen) Get the previous generation (in LRU order).
long	getRequiredByteNumber() get the number of bytes the garbage collector needs to collect to keep the cache in good state, it will only move the resource to the delete list, another check has to be done to save physical space
CacheSerializer	getSerializer() return the serializer used by the cache
StoreState	getState()
long	getStoredByteCount() get the number of bytes used phisycally by this cache
CacheSweeper	getSweeper() return the cache sweeper used by the cache
long	getSyncDelay() Get the synchronization delay between to sync, in milliseconds
CacheValidator	getValidator() return the cache validator used by the cache
void	initialize(CacheFilter filter) initialize this CacheStore, and get some infos from the parent, aka the cache filter
protected CacheGeneration	loadGeneration(CacheGeneration cg) Load the given generation and unload the LRU loaded generation if necessary.
protected void	loadGenerations() Load the generations.
protected void	loadState() Load the store state
boolean	propertyChanged(java.lang.String name) Property monitoring for the CacheStore.
protected void	removeResource(CacheGeneration cg, CachedResource cr) Remove the given CachedResource from the given CacheGeneration.
protected void	resizeGeneration(CacheGeneration cg, CachedResource cr) Resize the generation in order to be able to store the given Resource.
protected void	saveGeneration(CacheGeneration cg) Save a generation.
protected void	saveState() Save the current state
boolean	storeCachedResource(CachedResource cr) Store a newly created (or updated) CachedResource.
boolean	storeCachedResource(CachedResource cr, long oldsize) Store a newly created (or updated) CachedResource.
void	sync() synchronize the internal database with the storage
java.lang.String	toString()
protected void	unloadGeneration(CacheGeneration cg) UnLoad a "loaded" generation.
CachedResource	updateResourceGeneration(CachedResource cr) update this cached resource from generation x ot the latest
protected void	updateSweeperPriority() update the mode of the sweeper according to the state of the cache store,

Methods inherited from class java.lang.Object

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

Field Detail

CACHE_DIRECTORY_P

public static final java.lang.String CACHE_DIRECTORY_P

Name of the property giving the cache's directory. This property defaults to the current directory.

See Also:

Constant Field Values

STORE_SIZE_P

public static final java.lang.String STORE_SIZE_P

The name of the properties indicating the storesize of the cache (in bytes). This property will give the value of the disk-based cache size. This value only takes into account the size of the entities saved, not the size of the associated headers, and not the physical size on the disc.

This property defaults to 20 Mbytes.

See Also:

Constant Field Values

GARBAGE_COLLECTION_THRESHOLD_P

public static final java.lang.String GARBAGE_COLLECTION_THRESHOLD_P

Name of the property used to knkow the percentage of bytes to be kept after a garbage collection It defaults to 0.80 (80% of the cache size)

See Also:

Constant Field Values

FILE_SIZE_RATIO_P

public static final java.lang.String FILE_SIZE_RATIO_P

Name of the property indicating the max size for files to be cached. This property gives the ratio (relative to the cache size) of the number of bytes a single entry is able to occupy.

The ratio should be given as a floating point value between 0 and 1. If set to 0.1 and the cache size is 5000000, files larger then 500000 will not be cached (except if garbage collection is disbabled).

This property defaults to 0.1. Note that the generation size will be taken from this threshold

See Also:

Constant Field Values

GARBAGE_COLLECTION_ENABLED_P

public static final java.lang.String GARBAGE_COLLECTION_ENABLED_P

Name of the property enabling garbage collection of the cache. This property defaults to true.

See Also:

Constant Field Values

SYNCHRONIZATION_DELAY_P

public static final java.lang.String SYNCHRONIZATION_DELAY_P

Name of the property indicating the amount of time in second between two synchronization of the database (aka dump on disk) Milliseconds

See Also:

Constant Field Values

GENERATION_COMPACT_DELAY_P

public static final java.lang.String GENERATION_COMPACT_DELAY_P

Name of the property indicating the amount of time in second between two attempts to compact generations. In milliseconds

See Also:

Constant Field Values

MAX_CACHED_RESOURCES_P

public static final java.lang.String MAX_CACHED_RESOURCES_P

Name of the property indicating the maximal number of resources the cache can load in memory (not the content of the resources)

See Also:

Constant Field Values

MAX_GENERATIONS_P

public static final java.lang.String MAX_GENERATIONS_P

Name of the property indicating the maximal number of generations in this cache store

See Also:

Constant Field Values

GENERATION_FILENAME

public static final java.lang.String GENERATION_FILENAME

See Also:

Constant Field Values

props

protected ObservableProperties props

The properties we initialized ourself from.

Constructor Detail

CacheStore

public CacheStore()

Method Detail

propertyChanged

public boolean propertyChanged(java.lang.String name)

Property monitoring for the CacheStore. The CacheStore allows you to dynamically (typically through the property setter) change the class of the sweeper, the validator, the size...

Specified by:

propertyChanged in interface PropertyMonitoring

Parameters:

name - The name of the property that has changed.

Returns:

A boolean, true if the change was made, false otherwise.

getState

public StoreState getState()

getSweeper

public CacheSweeper getSweeper()

return the cache sweeper used by the cache

Returns:

an instance of CacheSweeper

getSerializer

public CacheSerializer getSerializer()

return the serializer used by the cache

Returns:

an instance of Serializer

getValidator

public CacheValidator getValidator()

return the cache validator used by the cache

Returns:

an instance of CacheValidator

getNextGeneration

public CacheGeneration getNextGeneration(CacheGeneration gen)

Get the next generation (in LRU order).

Parameters:

gen - the current generation

Returns:

a generation

getPrevGeneration

public CacheGeneration getPrevGeneration(CacheGeneration gen)

Get the previous generation (in LRU order).

Parameters:

gen - the current generation

Returns:

a generation

getMRUGeneration

public CacheGeneration getMRUGeneration()

Get the last generation, ie the Most recently used generation

Returns:

a CacheGeneration, the most recently used one

getMRUGenerationRatio

public float getMRUGenerationRatio()

Get the fill ratio of the last generation (the most recently used)

getLRUGeneration

public CacheGeneration getLRUGeneration()

Get the LRU generation, ie the Least recently used generation

Returns:

a CacheGeneration, the least recently used one

getLRULoadedGeneration

public CacheGeneration getLRULoadedGeneration()

Get the oldest loaded generation

Returns:

a generation

getSyncDelay

public long getSyncDelay()

Get the synchronization delay between to sync, in milliseconds

Returns:

a long, the number of milliseconds

getCompactGenerationDelay

public long getCompactGenerationDelay()

Get the delay between two attempts to compact the generations.

Returns:

a long, the number of milliseconds

addNewGeneration

protected CacheGeneration addNewGeneration()
                                    throws InvalidCacheException

Create and add a new Generation. WARNING, this method is not synchronized.

Returns:

the newly created generation or null if the max number of generations is reached or it the current size of the cache (in memory) is too big to accept a new generation.

Throws:

InvalidCacheException - if the cache is corrupted

loadGeneration

protected CacheGeneration loadGeneration(CacheGeneration cg)
                                  throws InvalidCacheException

Load the given generation and unload the LRU loaded generation if necessary.

Parameters:

cg - the generation to load

Throws:

InvalidCacheException - if the cache is corrupted

unloadGeneration

protected void unloadGeneration(CacheGeneration cg)
                         throws InvalidCacheException

UnLoad a "loaded" generation. WARNING: not synchronized.

Parameters:

the - loaded generation

Throws:

InvalidCacheException - if the cache is corrupted

saveGeneration

protected void saveGeneration(CacheGeneration cg)
                       throws InvalidCacheException

Save a generation.

Parameters:

the - generation to be saved

Throws:

InvalidCacheException - if the cache is corrupted

loadGenerations

protected void loadGenerations()
                        throws InvalidCacheException

Load the generations. Only a subset of the generations will actually be loaded, some generations will only have a description (URLs, size) in memory. This method load some generations (until cr_limit is reached) and the remaining generations (if any) will only be a set of CachedResourceDescription.

Throws:

InvalidCacheException

loadState

protected void loadState()

Load the store state

saveState

protected void saveState()

Save the current state

getRequiredByteNumber

public long getRequiredByteNumber()

get the number of bytes the garbage collector needs to collect to keep the cache in good state, it will only move the resource to the delete list, another check has to be done to save physical space

Returns:

a long, the number of bytes to save

getCachedByteCount

public long getCachedByteCount()

get the cached size of this cache

Returns:

a long, the number of bytes cached

getStoredByteCount

public long getStoredByteCount()

get the number of bytes used phisycally by this cache

Returns:

a long, the number of bytes cached

getCachedByteFree

public long getCachedByteFree()

get the number of bytes available for the cache memory

Returns:

a long, the number of bytes free

sync

public void sync()

synchronize the internal database with the storage

removeResource

protected void removeResource(CacheGeneration cg,
                              CachedResource cr)
                       throws NoSuchResourceException

Remove the given CachedResource from the given CacheGeneration. WARNING: not synchronized

Throws:

NoSuchResourceException - if this resource was not in this generation

getCachedResource

public CachedResource getCachedResource(java.lang.String url)
                                 throws InvalidCacheException

Get a cached resource relative to the given URL. WARNING: the CachedResource returned is no more in the CacheStore.

Parameters:

url - the URL of the CachedResource

Returns:

a CachedResource or null

Throws:

InvalidCacheException - if the cache is corrupted

See Also:

storeCachedResource(org.w3c.www.protocol.http.cache.CachedResource)

getCachedResource

public CachedResource getCachedResource(CachedResource cr)
                                 throws InvalidCacheException

extract a cached resource from the store

Parameters:

the - cached resource to be extracted

Returns:

the extracted cached resource

Throws:

InvalidCacheException - if the cache is corrupted

resizeGeneration

protected void resizeGeneration(CacheGeneration cg,
                                CachedResource cr)

Resize the generation in order to be able to store the given Resource.

Parameters:

cg - the generation to resize

cr - the CachedResource to store.

getCachedResourceReference

public CachedResource getCachedResourceReference(java.lang.String url)
                                          throws InvalidCacheException

Get a cached resource relative to the given URL. WARNING: the CachedResource returned is still in the cache store!

Parameters:

url - the URL of the CachedResource

Returns:

a CachedResource or null

Throws:

InvalidCacheException - if the cache is corrupted

See Also:

storeCachedResource(org.w3c.www.protocol.http.cache.CachedResource)

updateResourceGeneration

public CachedResource updateResourceGeneration(CachedResource cr)
                                        throws InvalidCacheException

update this cached resource from generation x ot the latest

Parameters:

the - cached resource to be updated

Returns:

the updated

Throws:

InvalidCacheException - if the cache is corrupted

storeCachedResource

public boolean storeCachedResource(CachedResource cr)
                            throws InvalidCacheException

Store a newly created (or updated) CachedResource.

Parameters:

cr - the CachedResource to store

Returns:

true if the resource has been cached

Throws:

InvalidCacheException - if the cache is corrupted

storeCachedResource

public boolean storeCachedResource(CachedResource cr,
                                   long oldsize)
                            throws InvalidCacheException

Store a newly created (or updated) CachedResource.

Parameters:

cr - the CachedResource to store

Returns:

true if the resource has been cached

Throws:

InvalidCacheException - if the cache is corrupted

getNewEntryFile

protected java.io.File getNewEntryFile()

allocate a new name for the next cached resource. This method create some directories if needed.

Returns:

a File, used to dump the entry

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

checkDirs

protected void checkDirs()

Check the subdirectories. Create them if necessary.

cleanCacheDir

protected int cleanCacheDir()

Clean the Cache directory, remove unused files.

Returns:

the number of files deleted.

updateSweeperPriority

protected void updateSweeperPriority()

update the mode of the sweeper according to the state of the cache store,

compactGenerations

protected void compactGenerations()

Compact our generations The algorithm is the following, If the number of generation is the maximum number allowed, then a check is done from the the generation after the MRU one and if the sum of two generation can fit into one, it is done, and the generation is removed from the list

checkState

protected void checkState()

used for debugging, display some internal information about the state of the cache

initialize

public void initialize(CacheFilter filter)
                throws InvalidCacheException

initialize this CacheStore, and get some infos from the parent, aka the cache filter

Parameters:

filter - a CacheFilter, our parent

Throws:

InvalidCacheException - if the cache not initialized