[infinispan-issues] [JBoss JIRA] (ISPN-4132) Group-based eviction

[Dan Berindei (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-4132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12959603#comment-12959603 ] 

Dan Berindei commented on ISPN-4132:
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Sure, S.A being accessed recently means S was also accessed recently, for any attribute A of S. But the reverse is not true: S being accessed recently doesn't mean that S.A was also accessed recently. So at any time it might make sense to keep in memory some of the attributes of S, but not all of them.

The only reason I would see to force a session to be passivated or activated all at once is if the JEE standard specifically allows the user to configure the number of sessions to be stored in memory. But even so, I think implementing group-based eviction in Infinispan would be way too complex, and storing each session in a single entry (like an {{AtomicMap}}) would be simpler.
                
> Group-based eviction
> --------------------
>
>                 Key: ISPN-4132
>                 URL: https://issues.jboss.org/browse/ISPN-4132
>             Project: Infinispan
>          Issue Type: Feature Request
>          Components: Eviction
>    Affects Versions: 6.0.2.Final
>            Reporter: Paul Ferraro
>            Assignee: Dan Berindei
>
> Currently, Infinispan only supports size-based eviction.   We can configure a cache with a specific max-entries, so if the size exceeds this value infinispan will evict any surplus entries.
> However, if the cache has grouping enabled, it is perhaps more useful to use group-based eviction.  In this scenario, max-entries would be interpreted as "max-groups", and infinispan would evict entire groups of cache entries if the number of groups exceeds this value.
> In WildFly, web sessions make use of grouping.  A single web session will map to a single group of multiple cache entries, where the number of entries is not necessarily the same for a given session.  In this case, evicting per cache entry does not make sense - all entries of a session should be evicted or not at all.  Also, users can specify the max number of sessions they want to remain in memory.  Until infinispan supports group-based eviction, translating this value to an appropriate max-entries is cumbersome and imprecise.

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