com.espertech.esper.epl.db

Class DataCacheExpiringImpl

java.lang.Object

com.espertech.esper.epl.db.DataCacheExpiringImpl

All Implemented Interfaces:

DataCache, ScheduleHandleCallback

public class DataCacheExpiringImpl
extends Object
implements DataCache, ScheduleHandleCallback

Implements an expiry-time cache that evicts data when data becomes stale after a given number of seconds.

The cache reference type indicates which backing Map is used: Weak type uses the WeakHashMap, Soft type uses the apache commons ReferenceMap, and Hard type simply uses a HashMap.

Constructor Summary

Constructors

Constructor and Description
DataCacheExpiringImpl(double maxAgeSec, double purgeIntervalSec, ConfigurationCacheReferenceType cacheReferenceType, SchedulingService schedulingService, long scheduleSlot, EPStatementAgentInstanceHandle epStatementAgentInstanceHandle, TimeAbacus timeAbacus) Ctor.

Method Summary

Modifier and Type	Method and Description
void	destroy()
EventTable[]	getCached(Object[] methodParams, int numLookupKeys) Ask the cache if the keyed value is cached, returning a list or rows if the key is in the cache, or returning null to indicate no such key cached.
protected double	getMaxAgeSec() Returns the maximum age in milliseconds.
double	getPurgeIntervalSec()
protected long	getSize() Returns the current cache size.
boolean	isActive() Returns true if the cache is active and currently caching, or false if the cache is inactive and not currently caching
void	put(Object[] methodParams, int numLookupKeys, EventTable[] rows) Puts into the cache a key and a list of rows, or an empty list if zero rows.
void	scheduledTrigger(EngineLevelExtensionServicesContext engineLevelExtensionServicesContext) Callback that is invoked as indicated by a schedule added to the scheduling service.

Methods inherited from class java.lang.Object

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

Constructor Detail

DataCacheExpiringImpl

public DataCacheExpiringImpl(double maxAgeSec,
                             double purgeIntervalSec,
                             ConfigurationCacheReferenceType cacheReferenceType,
                             SchedulingService schedulingService,
                             long scheduleSlot,
                             EPStatementAgentInstanceHandle epStatementAgentInstanceHandle,
                             TimeAbacus timeAbacus)

Ctor.

Parameters:

maxAgeSec - is the maximum age in seconds

purgeIntervalSec - is the purge interval in seconds

cacheReferenceType - indicates whether hard, soft or weak references are used in the cache

schedulingService - is a service for call backs at a scheduled time, for purging

scheduleSlot - slot for scheduling callbacks for this cache

epStatementAgentInstanceHandle - is the statements-own handle for use in registering callbacks with services

timeAbacus - time abacus

Method Detail

getCached

public EventTable[] getCached(Object[] methodParams,
                              int numLookupKeys)

Description copied from interface: DataCache

Ask the cache if the keyed value is cached, returning a list or rows if the key is in the cache, or returning null to indicate no such key cached. Zero rows may also be cached.

Specified by:

getCached in interface DataCache

Parameters:

methodParams - is the keys to look up in the cache

numLookupKeys - number of method param keys, from the start, that are for cache lookup

Returns:

a list of rows that can be empty is the key was found in the cache, or null if the key is not found in the cache

put

public void put(Object[] methodParams,
                int numLookupKeys,
                EventTable[] rows)

Description copied from interface: DataCache

Puts into the cache a key and a list of rows, or an empty list if zero rows.

The put method is designed to be called when the cache does not contain a key as determined by the get method. Implementations typically simply overwrite any keys put into the cache that already existed in the cache.

Specified by:

put in interface DataCache

Parameters:

methodParams - is the keys to the cache entry

numLookupKeys - number of method param keys, from the start, that are for cache lookup

rows - is a number of rows

getMaxAgeSec

protected double getMaxAgeSec()

Returns the maximum age in milliseconds.

Returns:

millisecon max age

getPurgeIntervalSec

public double getPurgeIntervalSec()

isActive

public boolean isActive()

Description copied from interface: DataCache

Returns true if the cache is active and currently caching, or false if the cache is inactive and not currently caching

Specified by:

isActive in interface DataCache

Returns:

true for caching enabled, false for no caching taking place

getSize

protected long getSize()

Returns the current cache size.

Returns:

cache size

scheduledTrigger

public void scheduledTrigger(EngineLevelExtensionServicesContext engineLevelExtensionServicesContext)

Description copied from interface: ScheduleHandleCallback

Callback that is invoked as indicated by a schedule added to the scheduling service.

Specified by:

scheduledTrigger in interface ScheduleHandleCallback

Parameters:

engineLevelExtensionServicesContext - is a marker interface for providing custom extension services passed to the triggered class

destroy

public void destroy()

Specified by:

destroy in interface DataCache