Bounded LRU Cache
A common use case. A cache data structure that:
- has a bounded maximum size and thus memory consumption (which in turn implies a cache eviction policy like LRU)
- is safe and performant for concurrent use
AFAICT, there’s nothing in the JDK or the concurrency JSRs that hits both these requirements. I googled and found the open source Concurrent Linked Hashmap library, which does.
[An incorrect comment about the project missing tests has been removed]
Unbounded Garbage Collectable Cache
If instead, you want a cache that will grow with use, but can be reclaimed if memory is short, then the use of a ConcurrentReferenceHashMap, configured with SoftReferences, is a good solution.
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ben manes said,
June 22, 2010 at 7:40 pm
Ben expressed his concern about a lack of tests over email. There are in fact ample tests and they are located under unittest/ in the release branch:
http://code.google.com/p/concurrentlinkedhashmap/source/browse/tags/release-1.0-LRU/
Thanks for the independent testing and contacting me with your concerns. All feedback is appreciated!
Best,
Ben
Ben Manes said,
September 28, 2010 at 3:19 pm
FYI,
We’ve completed integration of ConcurrentLinkedHashMap’s algorithm into MapMaker. This will be available in Guava r08.
This allows the combination of #maximumSize() to bound in the common case, *plus* soft-references to automatically evict if under load. The combination allows graceful degradation rather than OOME, while not suffering the penalty of soft references in the common case.