dk.heick.caching.persistences.file

Class AbstractIndexedFileValueManager<K extends Serializable,V>

java.lang.Object

dk.heick.caching.persistences.AbstractPersistenceValueManager<K,V>

dk.heick.caching.persistences.file.AbstractFileValueManager<K,V>

dk.heick.caching.persistences.file.AbstractIndexedFileValueManager<K,V>

Type Parameters:

K - the key type.

V - the valye type.

All Implemented Interfaces:

ValueManager<K,V>

Direct Known Subclasses:

DefaultIndexedSerializableFileValueManager, DefaultIndexedXmlFileValueManager

public abstract class AbstractIndexedFileValueManager<K extends Serializable,V>
extends AbstractFileValueManager<K,V>

A persisted file valuemanager which holds the Key to File relation stored in a file in the Caching Directory.
This file is named "persistencefilecache.ser" and is always in the root of the Caching Directory, and is owned by the ValueManager.
This ValueManager works that all keys get a random UUID string which is the filename the value is stored under.
This "UUID string" to "key" relation is stored in a index hashtable which is serialized to a file "persistencefilecache.ser" whenever X changes has been performed.
This X is set by "indexSaveInterval", set a 'good' value to minimized IO, but the higher the value, the higher the number of lost keys when a reboot is performed.
After "restore" and "cleanup" the "index" file is always persisted afterwards.

Since:

1.0

Author:

Frederik Heick

Field Summary

Fields

Modifier and Type	Field and Description
File	PERSISTENCE_STORAGE_INDEX_FILE
static String	PERSISTENCE_STORAGE_INDEX_FILENAME

Constructor Summary

Constructors

Constructor and Description
AbstractIndexedFileValueManager(CachingDirectory cachingDirectory, PersistencesRestoreMethod persistencesRestoreMethod, int indexSaveInterval) Constructor.

Method Summary

Modifier and Type	Method and Description
File	constructFile(K key, V value) Constructs a file using the Key and Value.
void	flush() This is ensures that any memory data that needs to be persisted is flushed.
int	getIndexSaveInterval() How many changes must be made before the index "File-to-Key" hashtable is persisted.
K	reconstructKey(File file) When restoring a persisted LRUCachingMap, we need the ability to reconstruct the Key.
int	removeAll() Remove all persisted values from the value "storage".
void	removeValue(AbstractValueWrapper<K,V> valueWrapper) Removes the value
abstract V	retrieveFileValue(DefaultFileValueWrapper<K,V> valueWrapper) Loads the value from the file in valueWrapper.
V	retrieveValue(AbstractValueWrapper<K,V> valueWrapper) Retrives value via the data contained in the ValueWrapper
abstract void	storeFileValue(DefaultFileValueWrapper<K,V> valueWrapper, K key, V value) This method shall the take the Value and stored it in a file given by the valueWrapper.
void	storeValue(AbstractValueWrapper<K,V> valueWrapper, K key, V value, Date expireDateTime) Stores the value and giving the ValueWrapper enough information to retrieve/remove it again.

Methods inherited from class dk.heick.caching.persistences.file.AbstractFileValueManager

cast, constructWrapper, getCachingDirectory, getFile, restore, updateExpireTime

Methods inherited from class dk.heick.caching.persistences.AbstractPersistenceValueManager

getLogger, getPersistencesRestoreMethod, isPersisted

Methods inherited from class java.lang.Object

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

Field Detail

PERSISTENCE_STORAGE_INDEX_FILENAME

public static final String PERSISTENCE_STORAGE_INDEX_FILENAME

See Also:

Constant Field Values

PERSISTENCE_STORAGE_INDEX_FILE

public final File PERSISTENCE_STORAGE_INDEX_FILE

Constructor Detail

AbstractIndexedFileValueManager

public AbstractIndexedFileValueManager(CachingDirectory cachingDirectory,
                                       PersistencesRestoreMethod persistencesRestoreMethod,
                                       int indexSaveInterval)
                                throws IllegalArgumentException,
                                       NullPointerException

Constructor.

Parameters:

cachingDirectory - the directory where to store the cached values.

persistencesRestoreMethod - the restore method, when reconstructing the LRUCachingMap.

indexSaveInterval - hint for how often many changes must happend before the index is persisted as file.
If the server is rebooted this is number of keys that can be lost from the cache, but this has to considered against a file save for every change.
If less or equal to one, every change will result in a index file save.
I would state that 1 percent of the maximum number of is a good value. (So if maximum numbers of keys in cache is 10000 than for every 100 changes the index file is persisted).

Throws:

IllegalArgumentException - if cachingDirectory isnt a valid directory.

NullPointerException - if persistencesRestoreMethod or cachingDirectory is null.

See Also:

CachingDirectory.validate()

Method Detail

storeValue

public final void storeValue(AbstractValueWrapper<K,V> valueWrapper,
                             K key,
                             V value,
                             Date expireDateTime)
                      throws RuntimeException

Description copied from interface: ValueManager

Stores the value and giving the ValueWrapper enough information to retrieve/remove it again.

Parameters:

valueWrapper - the wrapper instance to store the value or information about the value, this can be used to minimize the memory footprint.

key - the key

value - the value

expireDateTime - the expiration datetime for the key, this can be stored on a persisted key/value and used in case of a restore.

Throws:

RuntimeException - if for any reason the value could not be store.

removeAll

public final int removeAll()

Description copied from interface: ValueManager

Remove all persisted values from the value "storage".

Specified by:

removeAll in interface ValueManager<K extends Serializable,V>

Overrides:

removeAll in class AbstractFileValueManager<K extends Serializable,V>

Returns:

the number of values is removed.

getIndexSaveInterval

public final int getIndexSaveInterval()

How many changes must be made before the index "File-to-Key" hashtable is persisted.

Returns:

the number of changes before save of index.

retrieveValue

public final V retrieveValue(AbstractValueWrapper<K,V> valueWrapper)
                      throws RuntimeException

Description copied from interface: ValueManager

Retrives value via the data contained in the ValueWrapper

Parameters:

valueWrapper - the

Returns:

the Value

Throws:

RuntimeException - if for any reason the value could not be retrieved.

reconstructKey

public final K reconstructKey(File file)

Description copied from class: AbstractFileValueManager

When restoring a persisted LRUCachingMap, we need the ability to reconstruct the Key.
Typical the filename is the key, otherwise it might be something in the value.
Must take the CachingDirectory into account and only use the path from the base caching directory and below:

Specified by:

reconstructKey in class AbstractFileValueManager<K extends Serializable,V>

Parameters:

file - the file.

Returns:

the key based on the file, if not able to reconstruct the key, the file is deleted.

removeValue

public final void removeValue(AbstractValueWrapper<K,V> valueWrapper)
                       throws RuntimeException

Description copied from interface: ValueManager

Removes the value

Specified by:

removeValue in interface ValueManager<K extends Serializable,V>

Overrides:

removeValue in class AbstractFileValueManager<K extends Serializable,V>

Throws:

RuntimeException - if for any reason the value could not be removed.

constructFile

public final File constructFile(K key,
                                V value)

Description copied from class: AbstractFileValueManager

Constructs a file using the Key and Value.

Specified by:

constructFile in class AbstractFileValueManager<K extends Serializable,V>

Parameters:

key - the key

value - the value

Returns:

a file

flush

public final void flush()

This is ensures that any memory data that needs to be persisted is flushed.
This is the case with Indexed value managers.
This method must be called by the LRUCachingMap implementation after "cleanup" and after "restore". Forces a save of the key/file index file.

See Also:

LRUCachingMap.cleanup(), ValueManager.restore(LRUCachingMap)

storeFileValue

public abstract void storeFileValue(DefaultFileValueWrapper<K,V> valueWrapper,
                                    K key,
                                    V value)
                             throws RuntimeException

This method shall the take the Value and stored it in a file given by the valueWrapper.

Parameters:

valueWrapper - the value wrapper which holds the file.

key - the key.

value - the value.

Throws:

RuntimeException - if the value can not be stored in the file.

retrieveFileValue

public abstract V retrieveFileValue(DefaultFileValueWrapper<K,V> valueWrapper)

Loads the value from the file in valueWrapper.

Parameters:

valueWrapper - the value wrapper

Returns:

the value V.