org.cache2k.impl

Class ArcCache<K,T>

java.lang.Object

org.cache2k.impl.BaseCache<ArcCache.Entry,K,T>

org.cache2k.impl.ArcCache<K,T>

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<CacheEntry<K,T>>, Cache<K,T>, CacheSource<K,T>, CanCheckIntegrity, KeyValueSource<K,T>

public class ArcCache<K,T>
extends BaseCache<ArcCache.Entry,K,T>

Adaptive Replacement Cache implementation for cache2k. The algorithm itself is patented by IBM, so the implementation will probably never be available or used as default eviction algorithm. This implementation may be removed from the cache2k core package before 1.0.

The implemented algorithm changed from cache2k version 0.19 to 0.20. Within version 0.20 the eviction is separated from the general cache access, because of the consequent entry locking scheme an entry that is accessed, is always present in the cache. This means, the eviction is postponed to the end of the cache operation. The ARC algorithm was augmented to reflect this. This means for a cache operation that a newly inserted cache entry is also a candidate for eviction at the end of the operation.

Author:

Jens Wilke

See Also:

A Self-Tuning, Low Overhead Replacement Cache, Wikipedia: Adaptive Replacement Cache

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	ArcCache.Entry<K,T> An entry in the hash table

Nested classes/interfaces inherited from class org.cache2k.impl.BaseCache

BaseCache.Info, BaseCache.MyTimerTask, BaseCache.Tunable

Field Summary

Fields inherited from class org.cache2k.impl.BaseCache

bulkCacheSource, bulkGetCnt, clearedTime, entryExpiryCalculator, evictedButInHashCnt, evictedCnt, evictionNeeded, exceptionExpiryCalculator, exceptionMaxLinger, experimentalBulkCacheSource, expiredKeptCnt, expiredRemoveCnt, fetchButHitCnt, fetchCnt, fetchExceptionCnt, fetchMillis, hashSeed, info, internalExceptionCnt, keyMutationCount, keyType, loadHitCnt, loadMissCnt, loadNonFreshAndFetchedCnt, loadNonFreshCnt, lock, mainHash, mainHashCtrl, manager, maximumBulkFetchSize, maxLinger, maxSize, name, newEntryCnt, peekHitNotFreshCnt, peekMissCnt, putCnt, putNewEntryCnt, refreshCnt, refreshHash, refreshHashCtrl, refreshHitCnt, refreshPool, refreshSubmitFailedCnt, removedCnt, shutdownInitiated, shutdownWaitFuture, source, startedTime, storage, suppressedExceptionCnt, timer, timerCancelCount, timerService, touchedTime, TUNABLE, valueType, virginEvictCnt, waitForClear

Constructor Summary

Constructors

Constructor and Description
ArcCache()

Method Summary

Methods

Modifier and Type	Method and Description
protected ArcCache.Entry	checkForGhost(K key, int hc) Check whether we have an entry in the ghost table remove it from ghost and insert it into the replacement list.
protected ArcCache.Entry	findEvictionCandidate() Find an entry that should be evicted.
protected String	getExtraStatistics()
long	getHitCnt()
protected IntegrityState	getIntegrityState()
protected void	initializeHeapCache()
protected void	insertIntoReplacementList(ArcCache.Entry e) New cache entry, put it in the replacement algorithm structure
protected ArcCache.Entry<K,T>	newEntry() Emtpy, done by replace / checkForGhost.
protected void	recordHit(ArcCache.Entry e) Record an entry hit.
protected void	removeEntryFromReplacementList(ArcCache.Entry e)

Methods inherited from class org.cache2k.impl.BaseCache

calcNextRefreshTime, calculateHashEntryCount, checkClosed, checkCyclicListIntegrity, checkIntegrity, clear, clearLocalCache, clearTimingStatistics, close, conditionallyStartProcess, contains, destroy, evictEventually, expireEntry, fetch, fetchFromSource, fetchWithStorage, flush, get, getAll, getAll, getBulk, getCompleteName, getCyclicListEntryCount, getEntry, getEntryInternal, getExpiredCnt, getFetchesBecauseOfNewEntries, getFetchesInFlight, getInfo, getLatestInfo, getListEntryCount, getLocalSize, getLog, getName, getStorage, getTotalEntryCount, hasBackgroundRefreshAndServesExpiredValues, hasKeepAfterExpired, hasSharpTimeout, hasSuppressExceptions, init, insert, insert, insertAfterHeadCyclicList, insertEntryFromStorage, insertEntryFromStorage, insertFetched, insertInList, insertIntoHeadCyclicList, insertIntoTailCyclicList, insertOnPut, isClosed, iterateAllHeapEntries, iterateLocalAndStorage, iterator, lockAndRunForPurge, lookupEntry, lookupEntrySynchronized, lookupEntryUnsynchronized, lookupOrNewEntrySynchronized, modifiedHash, moveToFront, newEntry, peek, peekEntry, peekEntryInternal, prefetch, prefetch, prefetch, purge, put, putIfAbsent, remove, removeAllAtOnce, removeEntry, removeFromCyclicList, removeFromCyclicList, removeFromList, removeWithFlag, resetStorage, returnEntry, returnValue, setBulkCacheSource, setCacheConfig, setCacheManager, setEntryExpiryCalculator, setExceptionExpiryCalculator, setExperimentalBulkCacheSource, setExpirySeconds, setFeatureBit, setName, setRefreshController, setSource, setSource, stopStartTimer, timerEvent, toString, updateShutdownWaitFuture

Methods inherited from class java.lang.Object

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

Constructor Detail

ArcCache

public ArcCache()

Method Detail

getHitCnt

public long getHitCnt()

Specified by:

getHitCnt in class BaseCache<ArcCache.Entry,K,T>

recordHit

protected void recordHit(ArcCache.Entry e)

Description copied from class: BaseCache

Record an entry hit.

Specified by:

recordHit in class BaseCache<ArcCache.Entry,K,T>

insertIntoReplacementList

protected void insertIntoReplacementList(ArcCache.Entry e)

Description copied from class: BaseCache

New cache entry, put it in the replacement algorithm structure

Specified by:

insertIntoReplacementList in class BaseCache<ArcCache.Entry,K,T>

newEntry

protected ArcCache.Entry<K,T> newEntry()

Emtpy, done by replace / checkForGhost.

Specified by:

newEntry in class BaseCache<ArcCache.Entry,K,T>

checkForGhost

protected ArcCache.Entry checkForGhost(K key,
                           int hc)

Description copied from class: BaseCache

Check whether we have an entry in the ghost table remove it from ghost and insert it into the replacement list. null if nothing there. This may also do an optional eviction if the size limit of the cache is reached, because some replacement algorithms (ARC) do this together.

Overrides:

checkForGhost in class BaseCache<ArcCache.Entry,K,T>

removeEntryFromReplacementList

protected void removeEntryFromReplacementList(ArcCache.Entry e)

Overrides:

removeEntryFromReplacementList in class BaseCache<ArcCache.Entry,K,T>

findEvictionCandidate

protected ArcCache.Entry findEvictionCandidate()

Description copied from class: BaseCache

Find an entry that should be evicted. Called within structure lock. After doing some checks the cache will call BaseCache.removeEntryFromReplacementList(Entry) if this entry will be really evicted. Pinned entries may be skipped. A good eviction algorithm returns another candidate on sequential calls, even if the candidate was not removed.

Rationale: Within the structure lock we can check for an eviction candidate and may remove it from the list. However, we cannot process additional operations or events which affect the entry. For this, we need to acquire the lock on the entry first.

Overrides:

findEvictionCandidate in class BaseCache<ArcCache.Entry,K,T>

initializeHeapCache

protected void initializeHeapCache()

Overrides:

initializeHeapCache in class BaseCache<ArcCache.Entry,K,T>

getExtraStatistics

protected String getExtraStatistics()

Overrides:

getExtraStatistics in class BaseCache<ArcCache.Entry,K,T>

getIntegrityState

protected IntegrityState getIntegrityState()

Overrides:

getIntegrityState in class BaseCache<ArcCache.Entry,K,T>