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

[Sanne Grinovero (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38746#action_38746 ] 

Sanne Grinovero commented on HSEARCH-598:
-----------------------------------------

hi, the dataset size is not relevant, the number of threads enabled on the indexer are.
each thread might potentially need an hibernate session, and this number varies with the actual data but of course will never be above the number of threads.
Until we find a better way, to be safe always have a higher number of connections than the total of each set of threads of the massindexer, and it won't hurt to have a couple of spare ones.
I'll figure out what the exact numbers are and document it, but I don't think we can actually prevent users from setting this wrong - still looking for ideas and suggestions are welcome.

> 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, 3.3.0.Beta2
>
>
> 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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