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From "Phil Steitz (JIRA)" <>
Subject [jira] Resolved: (DBCP-294) Memory leak in XA Implementation
Date Sun, 25 Oct 2009 16:29:59 GMT


Phil Steitz resolved DBCP-294.

    Resolution: Fixed

Applied the patch with the following changes/additions:

1) Modified BasicDataSource to allow BasicManagedDataSource to use PoolableManagedConnectionFactory
2) Added a "full" constructor for PMCF so BasicManagedDataSource properties can be set
3) Made initializeConnection protected in PCF and added call to this in PMCF#makeObject()
4) Modified PoolableManagedConnection constructor to not ignore abandonedConfig parameter
4) Added a test case demonstrating the bug

Thanks for the patch!

> Memory leak in XA Implementation
> --------------------------------
>                 Key: DBCP-294
>                 URL:
>             Project: Commons Dbcp
>          Issue Type: Bug
>    Affects Versions: 1.3, 1.4, 2.0
>         Environment: JDK5, Oracle 10G,Postgres 8.x
>            Reporter: Philippe Mouawad
>            Assignee: Phil Steitz
>            Priority: Critical
>             Fix For: 1.3
>         Attachments: memory.png,,,, TransactionRegistry-patch.txt
>   Original Estimate: 52h
>  Remaining Estimate: 52h
> Hello,
> We are been using Ofbiz with DBCP based implementation.
> Ofbiz uses a Head revision of DBCP (package org.apache.commons.dbcp.managed is the same
as current TRUNK) and geronimo-transaction-1.0.
> We are having recurrent OutOfMemory which occur on a 2 days basis.
> I analyzed the Heap Dump and I think have found the source of the problem:
> The Heap Dump shows a Retained Heap of 400Mo by org.apache.commons.dbcp.managed.TransactionRegistry#xaResources
> After analyzing more deeply, the leak seems to come from what is stored in xaResources
> xaResources.put(connection, xaResource);
> Values inside weak Hash map  will never be removed since XAResource holds a STRONG reference
on key (connection) through:
> org.apache.commons.dbcp.managed.LocalXAConnectionFactory$LocalXAResource through:
> public LocalXAResource(Connection localTransaction) {
>             this.connection = localTransaction;
>         }
> Found in WeakHashMap javadoc:
> Implementation note: The value objects in a WeakHashMap are held by ordinary strong references.
>>>>>>>>>>>>>Thus care should be taken to ensure that
value objects do not strongly refer to their own keys <<<<<<<<, either
directly or indirectly, since that will prevent the keys from being discarded. Note that a
value object may refer indirectly to its key via the WeakHashMap itself; that is, a value
object may strongly refer to some other key object whose associated value object, in turn,
strongly refers to the key of the first value object. One way to deal with this is to wrap
values themselves within WeakReferences before inserting, as in: m.put(key, new WeakReference(value)),
and then unwrapping upon each get. 
> Philippe Mouawad

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