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

[Michael Mogley (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38953#action_38953 ] 

Michael Mogley commented on HSEARCH-598:
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I'm saying this:

// The maximum number connections this indexer can have open at once.
indexer.setMaxConnections(10);

// Internally checks maxConnections. 7 < 10?  Ok to proceed.
indexer.fetchingThreads(7);

// Internally checks maxConnections. 7 already used.  Limit 5 to 3.
indexer.loadingThreads(5);

The heuristic would attempt to still create the indexer, but limit the number of threads to the max number of connections specified at the outset.  Alternatively, you could always just throw an exception if the math doesn't work out.  But I think having it try to configure itself and issue a warning would be more friendly.

> 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.CR1
>
>
> 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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