net.sf.ehcache.store
Class LruMemoryStore

java.lang.Object
  net.sf.ehcache.store.LruMemoryStore

All Implemented Interfaces:

Store

public class LruMemoryStore
extends java.lang.Object
implements Store

An implementation of a LruMemoryStore.

This uses LinkedHashMap as its backing map. It uses the LinkedHashMap LRU feature. LRU for this implementation means least recently accessed.

Version:

$Id$

Author:

Greg Luck

Nested Class Summary

class

LruMemoryStore.SpoolingLinkedHashMap An extension of LinkedHashMap which overrides LruMemoryStore.SpoolingLinkedHashMap.removeEldestEntry(java.util.Map.Entry) to persist cache entries to the auxiliary cache before they are removed.

Field Summary

protected Ehcache	cache The cache this store is associated with.
protected Store	diskStore The DiskStore associated with this MemoryStore.
protected java.util.Map	map Map where items are stored by key.
protected int	maximumSize The maximum size of the store (0 == no limit)
protected Status	status status.

Constructor Summary

LruMemoryStore(Ehcache cache, Store diskStore)
Constructor for the LruMemoryStore object The backing LinkedHashMap is created with LRU by access order.

Method Summary

boolean	bufferFull() Memory stores are never backed up and always return false
protected void	clear() Clears any data structures and places it back to its state when it was first created.
boolean	containsKey(java.lang.Object key) An unsynchronized check to see if a key is in the Store.
void	dispose() Prepares for shutdown.
protected void	doPut(Element element) Allow specialised actions over adding the element to the map.
protected void	evict(Element element) Evict the Element.
void	expireElements() Expire all elsments.
void	flush() Flush to disk only if the cache is diskPersistent.
Element	get(java.lang.Object key) Gets an item from the cache.
Policy	getEvictionPolicy()
java.lang.Object	getInternalContext() This should not be used, and will generally return null
java.lang.Object[]	getKeyArray() Gets an Array of the keys for all elements in the memory cache.
Element	getQuiet(java.lang.Object key) Gets an item from the cache, without updating statistics.
int	getSize() Returns the current cache size.
long	getSizeInBytes() Measures the size of the memory store by measuring the serialized size of all elements.
Status	getStatus() Gets the status of the MemoryStore.
int	getTerracottaClusteredSize() Returns nothing since a disk store isn't clustered
boolean	isCacheCoherent() Indicates whether this store provides a coherent view of all the elements in a cache.
boolean	isClusterCoherent() Returns true if the cache is in coherent mode cluster-wide.
protected boolean	isFull() An algorithm to tell if the MemoryStore is at or beyond its carrying capacity.
boolean	isNodeCoherent() Returns true if the cache is in coherent mode for the current node.
protected void	notifyExpiry(Element element) Before eviction elements are checked.
boolean	put(Element element) Puts an item in the cache.
boolean	putWithWriter(Element element, CacheWriterManager writerManager) Puts an item into the store and the cache writer manager in an atomic operation
Element	remove(java.lang.Object key) Removes an Element from the store.
void	removeAll() Remove all of the elements from the store.
Element	removeWithWriter(java.lang.Object key, CacheWriterManager writerManager) Removes an item from the store and the cache writer manager in an atomic operation.
void	setEvictionPolicy(Policy policy) Sets the eviction policy strategy.
void	setNodeCoherent(boolean coherent) Sets the cache in coherent or incoherent mode for the current node depending on the parameter.
protected void	spoolAllToDisk() Spools all elements to disk, in preparation for shutdown.
protected void	spoolToDisk(Element element) Puts the element in the DiskStore.
void	waitUntilClusterCoherent() This method waits until the cache is in coherent mode in all the connected nodes.

Methods inherited from class java.lang.Object

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

Field Detail

cache

protected Ehcache cache

The cache this store is associated with.

map

protected java.util.Map map

Map where items are stored by key.

diskStore

protected final Store diskStore

The DiskStore associated with this MemoryStore.

status

protected Status status

status.

maximumSize

protected int maximumSize

The maximum size of the store (0 == no limit)

Constructor Detail

LruMemoryStore

public LruMemoryStore(Ehcache cache,
                      Store diskStore)

Constructor for the LruMemoryStore object The backing LinkedHashMap is created with LRU by access order.

Method Detail

put

public final boolean put(Element element)
                  throws CacheException

Puts an item in the cache. Note that this automatically results in LruMemoryStore.SpoolingLinkedHashMap.removeEldestEntry(java.util.Map.Entry) being called.

Specified by:

put in interface Store

Parameters:

element - the element to add

Returns:

true if this is a new put for the key or element is null. Returns false if it was an update.

Throws:

CacheException

putWithWriter

public final boolean putWithWriter(Element element,
                                   CacheWriterManager writerManager)
                            throws CacheException

Puts an item into the store and the cache writer manager in an atomic operation

Specified by:

putWithWriter in interface Store

Returns:

true if this is a new put for the key or element is null. Returns false if it was an update.

Throws:

CacheException

doPut

protected void doPut(Element element)
              throws CacheException

Allow specialised actions over adding the element to the map.

Parameters:

element -

Throws:

CacheException

get

public final Element get(java.lang.Object key)

Gets an item from the cache.

The last access time in Element is updated.

Specified by:

get in interface Store

Parameters:

key - the cache key

Returns:

the element, or null if there was no match for the key

getQuiet

public final Element getQuiet(java.lang.Object key)

Gets an item from the cache, without updating statistics.

Specified by:

getQuiet in interface Store

Parameters:

key - the cache key

Returns:

the element, or null if there was no match for the key

remove

public final Element remove(java.lang.Object key)

Removes an Element from the store.

Specified by:

remove in interface Store

Parameters:

key - the key of the Element, usually a String

Returns:

the Element if one was found, else null

removeWithWriter

public final Element removeWithWriter(java.lang.Object key,
                                      CacheWriterManager writerManager)
                               throws CacheException

Removes an item from the store and the cache writer manager in an atomic operation.

Specified by:

removeWithWriter in interface Store

Throws:

CacheException

removeAll

public final void removeAll()
                     throws CacheException

Remove all of the elements from the store.

Specified by:

removeAll in interface Store

Throws:

CacheException

clear

protected final void clear()

Clears any data structures and places it back to its state when it was first created.

dispose

public final void dispose()

Prepares for shutdown.

Specified by:

dispose in interface Store

flush

public final void flush()

Flush to disk only if the cache is diskPersistent.

Specified by:

flush in interface Store

spoolAllToDisk

protected final void spoolAllToDisk()

Spools all elements to disk, in preparation for shutdown.

This revised implementation is a little slower but avoids using increased memory during the method.

spoolToDisk

protected void spoolToDisk(Element element)

Puts the element in the DiskStore. Should only be called if isOverflowToDisk is true

Relies on being called from a synchronized method

Parameters:

element - The Element

getStatus

public final Status getStatus()

Gets the status of the MemoryStore.

Specified by:

getStatus in interface Store

getKeyArray

public final java.lang.Object[] getKeyArray()

Gets an Array of the keys for all elements in the memory cache.

Does not check for expired entries

Specified by:

getKeyArray in interface Store

Returns:

An Object[]

getSize

public final int getSize()

Returns the current cache size.

Specified by:

getSize in interface Store

Returns:

The size value

getTerracottaClusteredSize

public final int getTerracottaClusteredSize()

Returns nothing since a disk store isn't clustered

Specified by:

getTerracottaClusteredSize in interface Store

Returns:

returns 0

containsKey

public final boolean containsKey(java.lang.Object key)

An unsynchronized check to see if a key is in the Store. No check is made to see if the Element is expired.

Specified by:

containsKey in interface Store

Parameters:

key - The Element key

Returns:

true if found. If this method return false, it means that an Element with the given key is definitely not in the MemoryStore. If it returns true, there is an Element there. An attempt to get it may return null if the Element has expired.

getSizeInBytes

public final long getSizeInBytes()
                          throws CacheException

Measures the size of the memory store by measuring the serialized size of all elements. If the objects are not Serializable they count as 0.

Warning: This method can be very expensive to run. Allow approximately 1 second per 1MB of entries. Running this method could create liveness problems because the object lock is held for a long period

Specified by:

getSizeInBytes in interface Store

Returns:

the size, in bytes

Throws:

CacheException

evict

protected final void evict(Element element)
                    throws CacheException

Evict the Element.

Evict means that the Element is:

• if, the store is diskPersistent, the Element is spooled to the DiskStore
• if not, the Element is removed.

Parameters:

element - the Element to be evicted.

Throws:

CacheException

notifyExpiry

protected final void notifyExpiry(Element element)

Before eviction elements are checked.

Parameters:

element -

isFull

protected final boolean isFull()

An algorithm to tell if the MemoryStore is at or beyond its carrying capacity.

expireElements

public void expireElements()

Expire all elsments.

This is a default implementation which does nothing. Expiry on demand is only implemented for disk stores.

Specified by:

expireElements in interface Store

bufferFull

public boolean bufferFull()

Memory stores are never backed up and always return false

Specified by:

bufferFull in interface Store

Returns:

true if the store write buffer is backed up.

getEvictionPolicy

public Policy getEvictionPolicy()

Specified by:

getEvictionPolicy in interface Store

Returns:

the current eviction policy. This may not be the configured policy, if it has been dynamically set.

See Also:

setEvictionPolicy(Policy)

setEvictionPolicy

public void setEvictionPolicy(Policy policy)

Sets the eviction policy strategy. The Store will use a policy at startup. The store may allow changing the eviction policy strategy dynamically. Otherwise implementations will throw an exception if this method is called.

Specified by:

setEvictionPolicy in interface Store

Parameters:

policy - the new policy

getInternalContext

public java.lang.Object getInternalContext()

This should not be used, and will generally return null

Specified by:

getInternalContext in interface Store

Returns:

some internal context (probably null)

waitUntilClusterCoherent

public void waitUntilClusterCoherent()

This method waits until the cache is in coherent mode in all the connected nodes. If the cache is already in coherent mode it returns immediately

It applies to coherent clustering mechanisms only e.g. Terracotta

Specified by:

waitUntilClusterCoherent in interface Store

setNodeCoherent

public void setNodeCoherent(boolean coherent)

Sets the cache in coherent or incoherent mode for the current node depending on the parameter. Calling setNodeCoherent(true) when the cache is already in coherent mode or calling setNodeCoherent(false) when already in incoherent mode will be a no-op.

It applies to coherent clustering mechanisms only e.g. Terracotta

Specified by:

setNodeCoherent in interface Store

Parameters:

coherent - true transitions to coherent mode, false to incoherent mode

isNodeCoherent

public boolean isNodeCoherent()

Returns true if the cache is in coherent mode for the current node. Returns false otherwise.

It applies to coherent clustering mechanisms only e.g. Terracotta

Specified by:

isNodeCoherent in interface Store

Returns:

true if the cache is in coherent mode cluster-wide, false otherwise

isClusterCoherent

public boolean isClusterCoherent()

Returns true if the cache is in coherent mode cluster-wide. Returns false otherwise.

It applies to coherent clustering mechanisms only e.g. Terracotta

Specified by:

isClusterCoherent in interface Store

Returns:

true if the cache is in coherent mode cluster-wide, false otherwise

isCacheCoherent

public boolean isCacheCoherent()

Indicates whether this store provides a coherent view of all the elements in a cache. Note that this is same as calling Store.isClusterCoherent() (introduced since 2.0) Use Store.isNodeCoherent() to find out if the cache is coherent in the current node in the cluster

Specified by:

isCacheCoherent in interface Store

Returns:

true if the store is coherent; or false if the store potentially splits the cache storage with another store or isn't internally coherent