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From "Pinaki Poddar (JIRA)" <>
Subject [jira] Commented: (OPENJPA-825) slices: hangs with multithreaded true
Date Thu, 26 Feb 2009 16:33:01 GMT


Pinaki Poddar commented on OPENJPA-825:

Two primary objectives or hard constraints
1. Slice must execute database operations in parallel. Otherwise the basic purpose of working
with distributed data in an efficient manner is defeated.
2. OpenJPA's threading model should not be altered. Threading model is hard to retrofit and
OpenJPA's current threading model is battle-tested. Any fundamental alteration is a risk not
worth taking.

One approach to meet the above criteria and address this difficult reported issue is to incorporate
a variation on threading model for Slice module. Let each slice run on a specialized SliceThread
which acts like a child of a parent 'user' thread. The parent thread is the thread that invoked
the Broker/EntityManager operation. When the control reaches to Slice for executing database
operation, let Slice spawn specialized SliceThread. Let a SliceThread use its parent's lock.
But do this only for Broker and not for Query (which has its own reentrant lock). 

> slices: hangs with multithreaded true
> -------------------------------------
>                 Key: OPENJPA-825
>                 URL:
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: slice
>    Affects Versions: 2.0.0
>            Reporter: Fernando
>            Assignee: Pinaki Poddar
>            Priority: Critical
>         Attachments: hang-multithread-2.jstack, hang-multithread.jstack, hang-multithread.txt
> When I turned on openjpa.Multithreaded as a possible fix for another bug, I see that
the system hangs.  Attached are going to be a log file, and jstack, showing how it system
hung on the very first query. ( it did execute a few find() operations, but those are not
executed via ParallelExecutor ).

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