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This document explains how the MRUMemoryStore and Swapping under
Cocoon executes.
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The MRUMemoryStore was developed to provide a standard algorithm to
store data in memory. For web-based applications the MRU (Most Recently Used) algorithm
is very suitable, because the object most frequently accessed is always on "top".
If configured, the objects are also swapped to the filesystem if the
MRUMemoryStore reached his configured max. object limit.
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The heart of the MRUMemoryStore ist combination of a LinkedList and a HashMap:
The LinkedList provides the queue mechanism, and the entries in the LinkedList
contain the key to the data in the HashMap. When caching a new entry in to the list,
the entry is inserted to the front of the list.
If the list is already full, the oldest data entry is removed from the Cache.
When requesting a entry, the store returns the object by key and inserts the requested key
on the top of the Cache.
This implementation keeps the most recent used objects in the store and provides the best
use of the machines memory.
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When the MRUMemoryStore is full or the JVM is at the heap size limit the
objects in the MRUMemoryStore are swapped to the Filesystem. The default
directory is "cache-dir" in the work-directory.
NOTE: The keys under Cocoon are Strings at the moment. Therefor the
filenames of the swapped objects can be very long. Especially Windows OS
flavours have problems with long filenames. This problem is well known and
we are working on that.
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 | Configuration of the MRUMemoryStore |  |
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