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From "marco polo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3982) Add LRU mechanism to address memory concerns and possibly pre-fetch entries
Date Mon, 31 Aug 2015 14:34:46 GMT
marco polo created ACCUMULO-3982:
------------------------------------

             Summary: Add LRU mechanism to address memory concerns and possibly pre-fetch
entries
                 Key: ACCUMULO-3982
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3982
             Project: Accumulo
          Issue Type: New Feature
          Components: client, tserver
    Affects Versions: 1.7.0, 1.6.3, 1.8.0
            Reporter: marco polo
             Fix For: 1.8.0


On larger systems, especially those of which may split frequently, I've seen churn in the
TabletLocator caches. Could we possibly pre-fetch entries for a table so that we don't constantly
access the metadata table for tablet locations. 

Additionally, instead of clearing the cache in the case of a miss or failure, could we simply
update those entries in the cache? If we do this we may minimize cache misses overall and
the need to scan the meta data table. If need be, we could have a threshold before clearing
the cache entirely if people see the need for that.

It would also be helpful to add an LRU cache ( or maybe even priority based LRU cache ). In
ACCUMULO-3549, we added a cache clear to TabletServer to avoid overwhelming memory. An LRU
cache might address this concern and make the clear cache call unnecessary.





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