2.9. Using Eviction Policies
Eviction policies are the counterpart to cache loaders. They are necessary to make sure the cache does not run out of memory and when the cache starts to fill, an eviction algorithm running in a separate thread evicts in-memory state and frees up memory. If configured with a cache loader, the state can then be retrieved from the cache loader if needed.
Eviction policies can be configured on a per-region basis, so different subtrees in the cache could have different eviction preferences. JBoss Cache ships with several eviction policies:
Detailed configuration and implementing custom eviction policies are discussed in the Chapter 10, Eviction.
org.jboss.cache.eviction.LRUPolicy- an eviction policy that evicts the least recently used nodes when thresholds are hit.org.jboss.cache.eviction.LFUPolicy- an eviction policy that evicts the least frequently used nodes when thresholds are hit.org.jboss.cache.eviction.MRUPolicy- an eviction policy that evicts the most recently used nodes when thresholds are hit.org.jboss.cache.eviction.FIFOPolicy- an eviction policy that creates a first-in-first-out queue and evicts the oldest nodes when thresholds are hit.org.jboss.cache.eviction.ExpirationPolicy- an eviction policy that selects nodes for eviction based on an expiry time each node is configured with.org.jboss.cache.eviction.ElementSizePolicy- an eviction policy that selects nodes for eviction based on the number of key/value pairs held in the node.
