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| <document> |
| <properties> |
| <title>JCS Plugin Overview</title> |
| <author email="ASmuts@therealm.com">Aaron Smuts</author> |
| </properties> |
| <body> |
| <section name="JCS Plugin Overview"> |
| <p> JCS provides multiple auxiliaries which can be plugged into a |
| cache region, in a manner similar to adding Log4j appenders to a |
| logger. JCS auxiliaries are defined in the cache.ccf file. You can |
| specify which plugins a particular cache region should use.</p> |
| <p> There are four types of auxiliaries: (1) memory, (2) disk, (3) |
| lateral, and (4) remote. Each region is required to have one and |
| only one memory auxiliary. No other auxiliaries are required and any |
| possible combination of disk, lateral, and remote auxiliaries is |
| allowed. If you do not want to store items in memory, then the |
| maximum size for the memory caches can be set to 0 on a per region |
| basis.</p> |
| </section> |
| <section name="Memory Plugins"> |
| <p> Currently, JCS provides five memory management options: (1) |
| LRUMemoryCache, (2) LHMLRUMemoryCache, (3) MRUMemoryCache, (5) |
| FIFOMemoryCache, and (5) ARCMemoryCache. All memory caches restrict |
| the number of items that can be stored in memory per region. If a |
| disk cache is configured for the region, the items will be spooled |
| to disk when the memory capacity is reached. JCS enforces |
| configurable parameters such as time to live and maximum idle time. |
| Expired elements can be cleaned up by the ShrinkerThread, otherwise |
| they will be removed at the next retrieval attempt or when the |
| capacity is reached.</p> |
| <p> The LRUMemoryCache is the currently recommended plugin. Upon |
| misconfiguration it is used as the default. The LRUMemoryCache |
| removes the least recently used items when the cache is full.</p> |
| <p> The ARCMemoryCache is currently experimental. It implements an |
| adaptive replacement caching algorithm that combines an LRU and an |
| LFU that adapt to usage patterns.</p> |
| </section> |
| <section name="Disk Plugins"> |
| <p> JCS provides several disk swap options: indexed disk, HSQL, JISP, |
| and Berkeley DB JE. The IndexedDiskCache is the recommended disk |
| cache. It maintains the cached data on disk and the keys in memory |
| for the fastest possible lookup times. Writing to disk is done |
| asynchronously. Items are typically put in purgatory and queued for |
| background disk writing. While in purgatory, the items remain |
| available.</p> |
| <p> In addition, JCS provides a disk auxiliary that uses the Berkeley |
| DB Java Edition for disk storage. JCS can effectively function as an |
| expiration manager and distribution mechanism on top of a Berkeley |
| DB JE.</p> |
| </section> |
| <section name="Lateral Plugins"> |
| <p> JCS provides two recommended lateral distribution options: TCP |
| socket server distribution and JGroups (or JavaGroups). There are |
| also several other experimental lateral distribution auxiliaries |
| using servlets, UDP, and xmlrpc.</p> |
| </section> |
| <section name="Remote Plugins"> |
| <p> JCS provides both an RMI and HTTP remote servers to manage |
| distribution of cached data. These can be paired for failover.</p> |
| </section> |
| </body> |
| </document> |