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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5661) Discard pooled readers for cold data
Date Wed, 26 Jun 2013 01:08:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13693556#comment-13693556
] 

Pavel Yaskevich commented on CASSANDRA-5661:
--------------------------------------------

LRU is more of a replacement strategy when you have distinct objects and fixed upper limit
(num items, memory), but in here we deal with mostly duplicate objects and the states where
num of items hardly overgrows queue so the problem is not handling replacement but rather
expiring items after some period of idling. I was thinking of doing something like ExpiringQueue
with the one (or set of timers) similar to Guava Cache. Which solves the problem of [C]RAR
instances being stuck in the cache for long periods of time even when read pattern have changed
and they are not useful anymore.
                
> Discard pooled readers for cold data
> ------------------------------------
>
>                 Key: CASSANDRA-5661
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5661
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.2.1
>            Reporter: Jonathan Ellis
>            Assignee: Pavel Yaskevich
>             Fix For: 1.2.7
>
>
> Reader pooling was introduced in CASSANDRA-4942 but pooled RandomAccessReaders are never
cleaned up until the SSTableReader is closed.  So memory use is "the worst case simultaneous
RAR we had open for this file, forever."
> We should introduce a global limit on how much memory to use for RAR, and evict old ones.

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