[hibernate-issues] [Hibernate-JIRA] Commented: (HSEARCH-598) MassIndexer freezes when pool size is too low

[Adrien (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=41925#action_41925 ] 

Adrien commented on HSEARCH-598:
--------------------------------

I fixed the problem for me by limiting the number of threads launched in executor in BatchCoordinator.doBatchWork(). I could give you a patch to allow to configure this number of threads (default to number of enity) is you agree to the idea.

But it wont fixed the true dead lock. One solution to really avoid the dead lock even with lots of threads it to obtain the connection not in the consumer/producer threads, but in the workspace threads. We may do that by changing OptionallyWrapInJTATransaction : If we obtain the session in the constructor of instead of in the run(), it will be executed in the workspace thread. We also need to start the transaction in the constructor because the database connection is only open there. I'm just wondering if opening and closing the transaction in different threads will be ok with JTA transaction.

> MassIndexer freezes when pool size is too low
> ---------------------------------------------
>
>                 Key: HSEARCH-598
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-598
>             Project: Hibernate Search
>          Issue Type: Bug
>          Components: documentation, massindexer
>    Affects Versions: 3.2.1
>         Environment: Hibernate Core 3.5.4, PostgreSQL 8.4.4
>            Reporter: I D
>            Assignee: Sanne Grinovero
>             Fix For: 3.2.2, 3.4.0
>
>
> In our application we use db connection pooling at the servlet container level - Jetty instantiates a com.mchange.v2.c3p0.ComboPooledDataSource. We've disabled Hibernate's connection pooling to avoid multiple connection pools.
> Soon after starting to use MassIndexer we noticed that it SOMETIMES freezes during operation - startAndWait() just hangs indefinitely. After some experimentation, we realized that during this freeze the connection pool is maxed out and all the 15 connections (c3p0's default value for maxPoolSize is 15) are active.
> We therefore experimented with various values for maxPoolSize and found that 10 or less always seems to cause freezes, whereas 20 or more seems to work fine consistently. In between is a grey area, where the freeze occurs inconsistently (this grey area may of course extend to maxPoolSize<=10 and/or maxPoolSize>=20, since our tests only provide a partial statistical sample).
> If this is expected behavior, the minimal pool size / number of required connections should be well documented.

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