net.sf.ehcache.constructs.refreshahead
Class RefreshAheadCache

java.lang.Object
  net.sf.ehcache.constructs.EhcacheDecoratorAdapter
      net.sf.ehcache.constructs.refreshahead.RefreshAheadCache

All Implemented Interfaces:

Cloneable, Ehcache, InternalEhcache

public class RefreshAheadCache
extends EhcacheDecoratorAdapter

A cache decorator which implements read ahead refreshing. Read ahead occurs when a cache entry is accessed prior to its expiration, and triggers a reload of the value in the background.

A significant attempt is made to ensure only one node of the cache works on a specific key at a time. There is no guarantee that every triggered refresh ahead case will be processed. As the maximum number of backlog entries is reached, refresh ahead requests will be dropped silently.

Provided the Number of threads per node * Number of nodes < the maximum backlog, only one node in the cluster will refresha given key at a time.

Author:

cschanck

Field Summary

Fields inherited from class net.sf.ehcache.constructs.EhcacheDecoratorAdapter

underlyingCache

Constructor Summary

RefreshAheadCache(Ehcache adaptedCache, RefreshAheadCacheConfiguration refreshConfig)
Create a Refresh Ahead Cache Adaptor with the specified configuration.

Method Summary

static Set<ExtendedStatistics.Statistic<Number>>	findBacklogStatistic(Ehcache cache) Find backlog statistic.
static Set<ExtendedStatistics.Statistic<Number>>	findDroppedStatistic(Ehcache cache) Find dropped statistic.
static Set<ExtendedStatistics.Statistic<Number>>	findOfferStatistic(Ehcache cache) Find offer statistic.
static Set<ExtendedStatistics.Statistic<Number>>	findProcessedStatistic(Ehcache cache) Find processed statistic.
static Set<ExtendedStatistics.Statistic<Number>>	findRefreshedStatistic(Ehcache cache) Find refreshed counter statistic.
Element	get(Object key) Gets an element from the cache.
Element	get(Serializable key) Gets an element from the cache.
long	getBacklogCount() Gets backlog count.
long	getDroppedCount() Gets dropped count.
String	getName() Gets the cache name.
long	getOfferCount() Gets offer count.
long	getProcessedCount() Gets processed count.
long	getRefreshSuccessCount() number of refreshes processed locally.

Methods inherited from class net.sf.ehcache.constructs.EhcacheDecoratorAdapter

acquireReadLockOnKey, acquireWriteLockOnKey, addPropertyChangeListener, bootstrap, calculateInMemorySize, calculateOffHeapSize, calculateOnDiskSize, clone, createQuery, disableDynamicFeatures, dispose, evictExpiredElements, flush, getAll, getAllWithLoader, getBootstrapCacheLoader, getCacheConfiguration, getCacheEventNotificationService, getCacheExceptionHandler, getCacheManager, getDiskStoreSize, getGuid, getInternalContext, getKeys, getKeysNoDuplicateCheck, getKeysWithExpiryCheck, getMemoryStoreSize, getOffHeapStoreSize, getQuiet, getQuiet, getRegisteredCacheExtensions, getRegisteredCacheLoaders, getRegisteredCacheWriter, getSearchAttribute, getSearchAttributes, getSize, getStatistics, getStatus, getWithLoader, getWriterManager, hasAbortedSizeOf, initialise, isClusterBulkLoadEnabled, isClusterCoherent, isDisabled, isElementInMemory, isElementInMemory, isElementOnDisk, isElementOnDisk, isExpired, isKeyInCache, isNodeBulkLoadEnabled, isNodeCoherent, isReadLockedByCurrentThread, isSearchable, isValueInCache, isWriteLockedByCurrentThread, load, loadAll, put, put, putAll, putIfAbsent, putIfAbsent, putQuiet, putWithWriter, recalculateSize, registerCacheExtension, registerCacheLoader, registerCacheWriter, registerDynamicAttributesExtractor, releaseReadLockOnKey, releaseWriteLockOnKey, remove, remove, remove, remove, removeAll, removeAll, removeAll, removeAll, removeAndReturnElement, removeElement, removePropertyChangeListener, removeQuiet, removeQuiet, removeWithWriter, replace, replace, setBootstrapCacheLoader, setCacheExceptionHandler, setCacheManager, setDisabled, setName, setNodeBulkLoadEnabled, setNodeCoherent, setTransactionManagerLookup, toString, tryReadLockOnKey, tryWriteLockOnKey, unregisterCacheExtension, unregisterCacheLoader, unregisterCacheWriter, waitUntilClusterBulkLoadComplete, waitUntilClusterCoherent

Methods inherited from class java.lang.Object

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

Constructor Detail

RefreshAheadCache

public RefreshAheadCache(Ehcache adaptedCache,
                         RefreshAheadCacheConfiguration refreshConfig)

Create a Refresh Ahead Cache Adaptor with the specified configuration. An auxiliary EhCache Cache will be created for the purposes of synchronization, so only one node in a clustered environment will refresh a key at a given time.

Parameters:

adaptedCache -

refreshConfig -

Method Detail

get

public Element get(Object key)
            throws IllegalStateException,
                   CacheException

Description copied from class: EhcacheDecoratorAdapter

Gets an element from the cache. Updates Element Statistics

Note that the Element's lastAccessTime is always the time of this get. Use Ehcache.getQuiet(Object) to peek into the Element to see its last access time with get

Specified by:

get in interface Ehcache

Overrides:

get in class EhcacheDecoratorAdapter

Parameters:

key - an Object value

Returns:

the element, or null, if it does not exist.

Throws:

IllegalStateException - if the cache is not Status.STATUS_ALIVE

CacheException

See Also:

Ehcache.isExpired(net.sf.ehcache.Element)

get

public Element get(Serializable key)
            throws IllegalStateException,
                   CacheException

Description copied from class: EhcacheDecoratorAdapter

Gets an element from the cache. Updates Element Statistics

Note that the Element's lastAccessTime is always the time of this get. Use Ehcache.getQuiet(Object) to peak into the Element to see its last access time with get

Specified by:

get in interface Ehcache

Overrides:

get in class EhcacheDecoratorAdapter

Parameters:

key - a serializable value

Returns:

the element, or null, if it does not exist.

Throws:

IllegalStateException - if the cache is not Status.STATUS_ALIVE

CacheException

See Also:

Ehcache.isExpired(net.sf.ehcache.Element)

getRefreshSuccessCount

public long getRefreshSuccessCount()

number of refreshes processed locally.

getName

public String getName()

Description copied from class: EhcacheDecoratorAdapter

Gets the cache name.

Specified by:

getName in interface Ehcache

Overrides:

getName in class EhcacheDecoratorAdapter

getOfferCount

public long getOfferCount()

Gets offer count.

Returns:

the offer count

getDroppedCount

public long getDroppedCount()

Gets dropped count.

Returns:

the dropped count

getProcessedCount

public long getProcessedCount()

Gets processed count.

Returns:

the processed count

getBacklogCount

public long getBacklogCount()

Gets backlog count.

Returns:

the backlog count

findRefreshedStatistic

public static Set<ExtendedStatistics.Statistic<Number>> findRefreshedStatistic(Ehcache cache)

Find refreshed counter statistic.

Parameters:

cache - the cache this statistic is attached to.

Returns:

the set

findOfferStatistic

public static Set<ExtendedStatistics.Statistic<Number>> findOfferStatistic(Ehcache cache)

Find offer statistic.

Parameters:

cache - the cache this statistic is attached to.

Returns:

the set

findDroppedStatistic

public static Set<ExtendedStatistics.Statistic<Number>> findDroppedStatistic(Ehcache cache)

Find dropped statistic.

Parameters:

cache - the cache

Returns:

the set

findProcessedStatistic

public static Set<ExtendedStatistics.Statistic<Number>> findProcessedStatistic(Ehcache cache)

Find processed statistic.

Parameters:

cache - the cache

Returns:

the set

findBacklogStatistic

public static Set<ExtendedStatistics.Statistic<Number>> findBacklogStatistic(Ehcache cache)

Find backlog statistic.

Parameters:

cache - the cache

Returns:

the set