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 java.lang.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

DataCacheExpiringImpl(double maxAgeSec, double purgeIntervalSec, ConfigurationCacheReferenceType cacheReferenceType, SchedulingService schedulingService, ScheduleSlot scheduleSlot, EPStatementAgentInstanceHandle epStatementAgentInstanceHandle)
Ctor.

Method Summary

EventTable[]	getCached(java.lang.Object[] lookupKeys) 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 long	getMaxAgeMSec() Returns the maximum age in milliseconds.
protected long	getPurgeIntervalMSec() Returns the purge interval in milliseconds.
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(java.lang.Object[] lookupKeys, EventTable[] rows) Puts into the cache a key and a list of rows, or an empty list if zero rows.
void	scheduledTrigger(ExtensionServicesContext extensionServicesContext) 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,
                             ScheduleSlot scheduleSlot,
                             EPStatementAgentInstanceHandle epStatementAgentInstanceHandle)

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

Method Detail

getCached

public EventTable[] getCached(java.lang.Object[] lookupKeys)

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:

lookupKeys - is the keys to look up in the cache

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(java.lang.Object[] lookupKeys,
                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:

lookupKeys - is the keys to the cache entry

rows - is a number of rows

getMaxAgeMSec

protected long getMaxAgeMSec()

Returns the maximum age in milliseconds.

Returns:

millisecon max age

getPurgeIntervalMSec

protected long getPurgeIntervalMSec()

Returns the purge interval in milliseconds.

Returns:

millisecond purge interval

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(ExtensionServicesContext extensionServicesContext)

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:

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