Ehcache 2.1 Monitoring

In my previous post Spring, AspectJ, Ehcache Method Caching Aspect

I demo'ed and described how and why to cache the results of methods. Now to enhance that, I did some more investigation into the latest release of ehcache available at Terracotta

With 2.1 they released a monitoring api, to allow you to monitor cache's real time within your runtime environment, this will allow to fine tune and manage any cache you may have... be that custom caching with something like my MethodCacheAspect or your applications' Hibernate caches. To setup and use the monitoring you will need to do the following (I am setting this up on weblogic 10.3)

I placed the following 4 jars into my domain/lib, this will be different for every application server, but as long as the following are in the relative classpath you should be ok.

• ehcache-core-2.1.0.jar
• ehcache-probe-1.0.0.jar
• slf4j-api-1.5.11.jar
• slf4j-jdk14-1.5.11.jar

So now for the configuration:

The ehcache.xml, needs to be in your classpath and have the following details:


Take note of the following that is added to the cache you want to monitor.



In the start up of the application server... in my case weblogic 10.3 you will see the following:
(it is a licensed product from terracotta, and I am only using in a development environment to tune my cache settings)

INFO: Initializing EHCache CacheManager
04 Jul 2010 6:18:24 PM net.sf.ehcache.distribution.RMICacheManagerPeerListener
WARNING: Explicitly setting the listener hostname to 'localhost' is not recommended. It will only work if all CacheManager peers are on the same machine.
04 Jul 2010 6:18:25 PM org.terracotta.ehcachedx.monitor.probe.ProbeDxService startBackend
INFO: Started probe at http://localhost:51115/monitor/list
04 Jul 2010 6:18:25 PM org.terracotta.ehcachedx.license.LicenseResolver resolveLicense
WARNING: No Ehcache Monitor license key found. This monitoring probe software is not licensed for production usage, and is only licensed for development usage. See LICENSE.txt for details. A temporary key will be generated for development usage. When the temporary key expires, the Ehcache monitoring probe capability will be suspended but your ability to continue to use Ehcache will not be affected. Please contact sales@terracottatech.com to request a license.
04 Jul 2010 6:18:25 PM org.terracotta.ehcachedx.license.LicenseResolver logLicense
INFO:
--------- Ehcache Monitor license key ---------
License type = DevOnly
License number = 0
Licensee = DevOnly User
Product = Ehcache Monitor
Capabilities = monitor
Expiration date = 2010-07-07
-----------------------------------------------
04 Jul 2010 6:18:25 PM org.terracotta.ehcachedx.monitor.probe.ProbeDxService$RegisterWithServer run
INFO: Null license registered


Now that it is up and running, you can browse to:
http://localhost:51115/monitor/list

There you will get a list of methods that allow you to query you live caches, or even check the status of the CacheManager with, "probeGetCacheManagerStatus( )" very handy if you want to monitor the health of your live application. We have had a couple occasions where we we getting exceptions calling another teams' services and it took a while to discover that the "Cache Manager is not alive" exception.

The Ehcache API is REST based service. You Should be able to to use a simple RestTemplate like I used in my Spring 3 RESTFul example to manipulate and query the API, or you can just use a standard web browser:

http://localhost:51115/monitor/probeGetCacheManagerStatus
Result:
STATUS_ALIVE

http://localhost:51115/monitor/probeGetCacheNames
Result:
testCache
restCache

http://localhost:51115/monitor/probeGetCacheElementMemorySize?cache=testCache
Result:
584

The full list of functions are:

AmountOfHistoryStoredOnMonitor( )
getSampledStatisticNames( )
getSamplingHistory( )
getSamplingSeconds( )
getVersion( )
probeEvictExpiredElements( cache )
probeFlushCache( cache )
probeGetAllCachesConfigAllValues( )
probeGetAllCachesSampledStatisticValues( name )
probeGetCacheConfigAllValues( cache )
probeGetCacheConfigNames( )
probeGetCacheConfigValue( cache, name )
probeGetCacheConfigValues( cache, name )
probeGetCacheCount( )
probeGetCacheElementCount( cache )
probeGetCacheElementCountDisk( cache )
probeGetCacheElementCountMemory( cache )
probeGetCacheElementMemorySize( cache )
probeGetCacheElementMetaDataAllValues( cache, key )
probeGetCacheElementMetaDataNames( )
probeGetCacheElementMetaDataValue( cache, key, name )
probeGetCacheElementMetaDataValues( cache, key, name )
probeGetCacheKeys( cache, count, [query] )
probeGetCacheManagerName( )
probeGetCacheManagerStatus( )
probeGetCacheNames( )
probeGetReplicationMode( )
probeGetSampledStatisticAllValues( cache )
probeGetSampledStatisticHistory( cache, name, [fromDateTime], [timeInterval], [offset] )
probeGetSampledStatisticValue( cache, name )
probeGetSampledStatisticValues( cache, name )
probeRemoveAllFromCache( cache )
probeRemoveFromCache( cache, key )
probeRemoveQueryFromCache( cache, query )


Some of these could be very valuable to fine tune you caching strategy. Knowing things like "probeGetCacheElementCountDisk", "probeGetCacheElementMemorySize" and being able to monitor them may allow you to tailor your Ehcache config for optimal usage and consequently better application performance.

Also "probeFlushCache" or "probeRemoveFromCache" allow you to clear out the cache in the case of a data change without having to reinitialize / restart your application.