CompositeCache Class

.NET API Reference for Oracle® Coherence Community Edition
(14.1.1.0)
E55634-01

ICache implementation that wraps two caches - a front cache (assumed to be "inexpensive" and probably "incomplete") and a back cache (assumed to be "complete" and "correct", but more "expensive") - using a read-through/write-through approach.

Inheritance Hierarchy

SystemObject
Tangosol.Net.CacheCompositeCache
Tangosol.Net.CacheNearCache

Namespace: Tangosol.Net.Cache
Assembly: Coherence (in Coherence.dll) Version: 14.1.1.1 (14.1.1.1)

Syntax

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public class CompositeCache : ICache, 
	IDictionary, ICollection, IEnumerable, ICacheStatistics, IDisposable

The CompositeCache type exposes the following members.

Constructors

	Name	Description
	CompositeCache(ICache, ICache)	Construct a CompositeCache using two specified caches: FrontCache (aka "cache", "near" or "shallow") BackCache (aka "actual", "real" or "deep")
	CompositeCache(ICache, ICache, CompositeCacheStrategyType)	Construct a CompositeCache using two specified caches: FrontCache (aka "cache", "near" or "shallow") BackCache (aka "actual", "real" or "deep") and using the specified front cache invalidation strategy.

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Properties

	Name	Description
	AverageGetMillis	Determine the average number of milliseconds per "get" invocation since the cache statistics were last reset.
	AverageHitMillis	Determine the average number of milliseconds per "get" invocation that is a hit.
	AverageMissMillis	Determine the average number of milliseconds per "get" invocation that is a miss.
	AveragePruneMillis	Determine the average number of milliseconds per cache pruning.
	AveragePutMillis	Determine the average number of milliseconds per "put" invocation since the cache statistics were last reset.
	BackCache	Obtain the back cache reference.
	CacheControl	Obtain the IConcurrentCache that should be used to synchronize the front cache modification access.
	CacheHits	Determine the rough number of cache hits since the cache statistics were last reset.
	CacheHitsMillis	Determine the total number of milliseconds (since that last statistics reset) for the "get" operations for which an entry existed in this cache.
	CacheMisses	Determine the rough number of cache misses since the cache statistics were last reset.
	CacheMissesMillis	Determine the total number of milliseconds (since that last statistics reset) for the "get" operations for which no entry existed in this map.
	CachePrunes	Determine the rough number of cache pruning cycles since the cache statistics were last reset.
	CachePrunesMillis	Determine the total number of milliseconds (since that last statistics reset) spent on cache pruning.
	CacheStatistics	Obtain the CacheStatistics for this cache.
	Count	Gets the number of elements contained in the BackCache.
	Entries	Gets a collection of ICacheEntry instances within the cache.
	FrontCache	Obtain the front cache reference.
	HitProbability	Determine the rough probability (0 <= p <= 1) that the next invocation will be a hit, based on the statistics collected since the last reset of the cache statistics.
	InvalidationHits	Determine the rough number of front cache invalidation hits since the cache statistics were last reset.
	InvalidationMisses	Determine the rough number of front cache invalidation misses since the cache statistics were last reset.
	InvalidationStrategy	Obtain the invalidation strategy used by this CompositeCache.
	IsCoherent	Determine if changes to the back cache affect the front cache so that data in the front cache stays in sync.
	IsFixedSize	Gets a value indicating whether the BackCache object has a fixed size.
	IsReadOnly	Gets a value indicating whether the BackCache object is read-only.
	IsSynchronized	Gets a value indicating whether access to the back cache is synchronized (thread safe).
	Item	Gets or sets the element with the specified key.
	Keys	Obtain an ICollection of the keys contained in this cache.
	SyncRoot	Gets an object that can be used to synchronize access to the back cache.
	TotalGets	Determine the total number of "get" operations since the cache statistics were last reset.
	TotalGetsMillis	Determine the total number of milliseconds spent on "get" operations since the cache statistics were last reset.
	TotalPuts	Determine the total number of "put" operations since the cache statistics were last reset.
	TotalPutsMillis	Determine the total number of milliseconds spent on "put" operations since the cache statistics were last reset.
	TotalRegisterListener	Determine the total number of RegisterListener(Object) operations since the cache statistics were last reset.
	Values	Obtain an ICollection of the values contained in this cache.

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Methods

	Name	Description
	Add	Associates the specified value with the specified key in this cache.
	Clear	Clears both the front and back caches.
	Contains	Check whether or not this cache contains a mapping for the specified key.
	CopyTo	Copies the elements of the BackCache to an Array, starting at a particular Array index.
	Dispose	Calls Release to release the resources associated with this cache.
	EnsureInvalidationStrategy	Ensure that a strategy has been choosen and that any appropriate global listeners have been registered.
	Equals	Compares the specified object with this dictionary for equality. (Overrides ObjectEquals(Object).)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetAll	Get the values for all the specified keys, if they are in the cache.
	GetEnumerator	Returns an enumerator that iterates through a cache.
	GetHashCode	Return the hash code value for this dictionary. (Overrides ObjectGetHashCode.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	Insert(Object, Object)	Associates the specified value with the specified key in this cache.
	Insert(Object, Object, Int64)	Associates the specified value with the specified key in this cache.
	InsertAll	Copies all of the mappings from the specified dictionary to this cache (optional operation).
	InstantiateBackCacheListener	Factory pattern: instantiate back cache listener.
	InstantiateFrontCacheListener	Factory pattern: instantiate front cache listener.
	InvalidateFront	Invalidate the key from the front.
	IsPriming	Check if the specified event is a "priming" one.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	RegisterDeactivationListener	Instantiate and register a DeactivationListener with the back cache.
	RegisterFrontListener	Register the global front cache listener.
	RegisterListener	Register the global back cache listener.
	RegisterListener(Object)	Register the back cache listener for the specified key.
	RegisterListeners	Register the back map listeners for the specified set of keys.
	Release	Release the CompositeCache.
	Remove	Remove the mapping for this key from this cache if present.
	RemoveKeyHolder	Remove the key holder from the ThreadLocal object.
	ResetFrontMap	Reset the front map.
	ResetHitStatistics	Reset the cache statistics.
	ResetInvalidationStrategy	Reset the "current invalidation strategy" flag.
	SetKeyHolder	Set up a thread local Set to hold all the keys that might be evicted from the front cache.
	ToString	For debugging purposes, format the contents of the CompositeCache in a human readable format. (Overrides ObjectToString.)
	TryLock	Lock the keys in the given set without blocking.
	UnregisterDeactivationListener	Unregister back cache deactivation listener.
	UnregisterFrontListener	Unregister the global front cache listener.
	UnregisterListener	Unregister the global back cache listener.
	UnregisterListener(Object)	Unregister the back cache listener for the specified key.
	UnregisterListeners	Unregister the back cache listener for the specified keys. Note: all the keys in the passed-in set must be locked and will be unlocked.
	Validate	Validate the front cache entry for the specified back cache event.

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Fields

	Name	Description
	m_strategyCurrent	The current invalidation strategy, which at times could be different from the target strategy.
	m_strategyTarget	The invalidation strategy that this cache is to use.
	s_tloKeys	The ThreadLocal to hold all the keys that are evicted while the front cache is updated during get or getAll operation.

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Remarks

If the back cache implements IObservableCache interface, the CompositeCache provides four different strategies of invalidating the front cache entries that have changed by other processes in the back cache:

ListenNone strategy instructs the cache not to listen for invalidation events at all. This is the best choice for raw performance and scalability when business requirements permit the use of data which might not be absolutely current. Freshness of data can be guaranteed by use of a sufficiently brief eviction policy for the front cache.
ListenPresent strategy instructs the CompositeCache to listen to the back cache events related only to the items currently present in the front cache. This strategy works best when each instance of a front cache contains distinct subset of data relative to the other front cache instances (e.g. sticky data access patterns).
ListenAll strategy instructs the CompositeCache to listen to all back cache events. This strategy is optimal for read-heavy tiered access patterns where there is significant overlap between the different instances of front caches.
ListenAuto strategy instructs the CompositeCache implementation to switch automatically between ListenPresent and ListenAll strategies based on the cache statistics.
ListenLogical strategy instructs the CompositeCache to listen to all back map events that are not synthetic. A synthetic event could be emitted as a result of eviction or expiration. With this invalidation stategy, it is possible for the front map to contain cache entries that have been synthetically removed from the back (though any subsequent re-insertion will cause the corresponding entries in the front map to be invalidated).

The front cache implementation is assumed to be thread safe; additionally any modifications to the front cache are allowed only after the corresponding lock is acquired against the CacheControl property.

Note:null values are not cached in the front cache and therefore this implementation is not optimized for caches that allow null values to be stored.

Reference

Tangosol.Net.Cache Namespace