[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2169) L2 Cache and Long transactions Memory Leak : OutOfMemoryException

[Sami Dalouche (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_28164 ] 

Sami Dalouche commented on HHH-2169:
------------------------------------

session.setCacheMode would probably fix the problem by having the same effect as disabling the L2 Cache. However, this would mean that L2 Cache and Long transactions cannot be used simultaneously, thus meaning that one has to choose between performance and data integrity....

> L2 Cache and Long transactions Memory Leak : OutOfMemoryException
> -----------------------------------------------------------------
>
>                 Key: HHH-2169
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2169
>             Project: Hibernate3
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.2.0.ga
>         Environment: [b]Hibernate version:[/b] 
> Hibernate Entity Manager 3.2.0, with Hibernate Core 3.2.0 and Hibernate Annotations 3.2.0
> [b]Mapping documents:[/b]
> Annotations
> [b]Full stack trace of any exception that occurs:[/b]
> Memory Heap Exception
> [b]Name and version of the database you are using:[/b]
> PosgreSQL 8.1
>            Reporter: Sami Dalouche
>
> Summary
> ---------
> When enabling L2 Cache (with either OScache and EhCache, both with a limitation on the max #of instances, so the problem shouldn't come from the cache manager), Hibernate cannot have long running transactions, otherwise, it results in a Memory Heap Exception...
> The problem does NOT happen if the L2 Cache is disabled !
> Details
> ----------
> - Configure the code to run in ONE transaction
> - Have a huge loop that inserts 2 million entries that are cacheable (@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)) 
> - flush() and clear() every 1000 entries, to periodically flush the cache
> => None of the entries are garbage collected. 
> => Using a profiler, it is possible to trace the owning objects of my domain classes to :
> - org.hibernate.action.EntityInsertAction ("instance" variable)
> - array / List (variable elementData)
> - variable "executions" in object .. class org.hibernate.engine.ActionQueue
> Remarks :
> - If the Query Cache is disabled, and the objects being inserted are NOT cacheable (no @Cache annotation), there is no problem
> - If the Query Cache is enabled, then, no matter whether the objects being inserted are cacheable or not, The entries are never garbage collected, and I get an OutOfMemoryException. (I see NO relationship between the Query Cache and my objects. I never query the objects, only save them !!)

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