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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DBCP-272) Contention for DriverManager when initializing multiple datasources
Date Sun, 25 Jan 2009 04:13:59 GMT

     [ https://issues.apache.org/jira/browse/DBCP-272?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Phil Steitz updated DBCP-272:
-----------------------------

    Fix Version/s: 1.3

> Contention for DriverManager when initializing multiple datasources 
> --------------------------------------------------------------------
>
>                 Key: DBCP-272
>                 URL: https://issues.apache.org/jira/browse/DBCP-272
>             Project: Commons Dbcp
>          Issue Type: Bug
>    Affects Versions: 1.2.2
>         Environment: Java HotSpot(TM) 64-Bit Server VM (1.6.0-b105 mixed mode) on Linux
>            Reporter: Adrian Woodhead
>             Fix For: 1.3
>
>         Attachments: catalina.out.stuck2
>
>
> This issue has been discussed in the commons user's mailing list between myself, Simon
Kitching and Phil Steitz. 
> In summary:
> I have a webapp deployed in tomcat containing 3 pooled datasources which are managed
by Spring. The webapp starts up OK and is immediately hit by a load of a few hundred requests
a second. It seems to handle a few hundred request and then just locks up entirely and stops
responding entirely. Attached is a stack trace obtained by doing kill -3 when in this state.
After discussion on the mailing list I changed the datasources to be non-lazy initialised
in spring but the issue still occurs. 
> Simon Kitching said:
> "The first thread is trying to initialise a postgresql driver and register it with DriverManager.
The driver registration is being triggered from a static initialiser block on the postgresql
driver class, so is executing from within the Class.forName method (and therefore the postgresql
driver Class object is locked by this thread).
> The second thread is trying to initialise a mysql driver and register it with DriverManager.
Again, the driver registration is being triggered from a static initialiser block on the mysql
driver class, so the mysql driver Class object is locked by this thread).
> But in both cases, the DriverManager needs to be initialised before anything can be registered.
The first thread appears to have run first, triggering the initialisation process, and the
second thread is blocked waiting for initialisation of DriverManager to complete before it
registers the mysql driver. 
> <snip/>
> Possibly dbcp should call DriverManager.getDrivers() internally on startup to avoid this
race... "

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