TreeCache 1.2.X allows a single eviction policy provider class to be configured for use by all regions. As of TreeCache 1.3.x each cache region can define its own eviction policy provider or it can use the eviction policy provider class defined at the cache level (1.2.x backwards compatibility)

Here is an example of a legacy 1.2.x EvictionPolicyConfig element to configure TreeCache for use with a single eviction policy provider

          <attribute name="EvictionPolicyClass">org.jboss.cache.eviction.LRUPolicy</attribute>
          <!-- Specific eviction policy configurations. This is LRU -->
          <attribute name="EvictionPolicyConfig">
             <config>
                <attribute name="wakeUpIntervalSeconds">5</attribute>
                <!-- Cache wide default -->
                <region name="/_default_">
                    <attribute name="maxNodes">5000</attribute>
                    <attribute name="timeToLiveSeconds">1000</attribute>
                </region>
                <region name="/org/jboss/data">
                    <attribute name="maxNodes">5000</attribute>
                    <attribute name="timeToLiveSeconds">1000</attribute>
                </region>
                <region name="/org/jboss/test/data">
                    <attribute name="maxNodes">5</attribute>
                    <attribute name="timeToLiveSeconds">4</attribute>
                </region>
                <region name="/test/">
                    <attribute name="maxNodes">10000</attribute>
                    <attribute name="timeToLiveSeconds">5</attribute>
                </region>
                <region name="/maxAgeTest/">
                   <attribute name="maxNodes">10000</attribute>
                   <attribute name="timeToLiveSeconds">8</attribute>
                   <attribute name="maxAgeSeconds">10</attribute>
                </region>
             </config>
          </attribute>
       

Here is an example of configuring a different eviction provider per region

      <attribute name="EvictionPolicyConfig">
         <config>
            <attribute name="wakeUpIntervalSeconds">5</attribute>
            <!-- Cache wide default -->
            <region name="/_default_" policyClass="org.jboss.cache.eviction.LRUPolicy">
               <attribute name="maxNodes">5000</attribute>
               <attribute name="timeToLiveSeconds">1000</attribute>
            </region>
            <region name="/org/jboss/data" policyClass="org.jboss.cache.eviction.LFUPolicy">
               <attribute name="maxNodes">5000</attribute>
               <attribute name="minNodes">1000</attribute>
            </region>
            <region name="/org/jboss/test/data"
	        policyClass="org.jboss.cache.eviction.FIFOPolicy">
               <attribute name="maxNodes">5</attribute>
            </region>
            <region name="/test/" policyClass="org.jboss.cache.eviction.MRUPolicy">
               <attribute name="maxNodes">10000</attribute>
            </region>
            <region name="/maxAgeTest/" policyClass="org.jboss.cache.eviction.LRUPolicy">
               <attribute name="maxNodes">10000</attribute>
               <attribute name="timeToLiveSeconds">8</attribute>
               <attribute name="maxAgeSeconds">10</attribute>
            </region>
         </config>
      </attribute>
       

Lastly, an example of mixed mode. In this scenario the regions that have a specific policy defined will use that policy. Those that do not will default to the policy defined on the entire cache instance.

      <attribute name="EvictionPolicyClass">org.jboss.cache.eviction.LRUPolicy</attribute>
      <!-- Specific eviction policy configurations. This is LRU -->
      <attribute name="EvictionPolicyConfig">
         <config>
            <attribute name="wakeUpIntervalSeconds">5</attribute>
            <!-- Cache wide default -->
            <region name="/_default_">
               <attribute name="maxNodes">5000</attribute>
               <attribute name="timeToLiveSeconds">1000</attribute>
            </region>
            <region name="/org/jboss/data" policyClass="org.jboss.cache.eviction.FIFOPolicy">
               <attribute name="maxNodes">5000</attribute>
            </region>
            <region name="/test/" policyClass="org.jboss.cache.eviction.MRUPolicy">
               <attribute name="maxNodes">10000</attribute>
            </region>
            <region name="/maxAgeTest/">
               <attribute name="maxNodes">10000</attribute>
               <attribute name="timeToLiveSeconds">8</attribute>
               <attribute name="maxAgeSeconds">10</attribute>
            </region>
         </config>
      </attribute>
       

TreeCache now allows reconfiguration of eviction policy providers programatically at runtime. An example of how to reconfigure at runtime and how to set an LRU region to have maxNodes to 12345 timeToLiveSeconds to 500 and maxAgeSeconds to 1000 programatically.

         // note this is just to show that a running TreeCache instance must be
         // retrieved somehow. How it is implemented is up to the implementor.
         TreeCache cache = getRunningTreeCacheInstance();

         org.jboss.cache.eviction.RegionManager regionManager = cache.getEvictionRegionManager();
         org.jboss.cache.eviction.Region region = regionManager.getRegion("/myRegionName");
         EvictionConfiguation config = region.getEvictionConfiguration();
         ((LRUConfiguration)config).setMaxNodes(12345);
         ((LRUConfiguration)config).setTimeToLiveSeconds(500);
         ((LRUConfiguration)config).setMaxAgeSeconds(1000);