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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DBCP-216) Improvement of error recovery in KeyedCPDSConnectionFactory
Date Tue, 20 Nov 2007 06:28:43 GMT

    [ https://issues.apache.org/jira/browse/DBCP-216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12543792
] 

Phil Steitz commented on DBCP-216:
----------------------------------

>From commons-dev post by Stephane Demurget 13-nov-07.  Shows not removing listener when
connection is removed from pc map causes an exception when a connection is returned when maxIdle
is reached.  

Thread [pool-5-thread-4] (Suspended (exception IllegalStateException))
       KeyedCPDSConnectionFactory.connectionClosed(ConnectionEvent) line:
265
       SybPooledConnection.notifyListeners(SQLException) line: 225
       SybConnectionProxy.close() line: 106
       SybPooledConnection.close() line: 166
       KeyedCPDSConnectionFactory.destroyObject(Object, Object) line: 175

       GenericKeyedObjectPool.returnObject(Object, Object) line: 997
       KeyedCPDSConnectionFactory.connectionClosed(ConnectionEvent) line:
268
       SybPooledConnection.notifyListeners(SQLException) line: 225
       SybConnectionProxy.close() line: 106
       ... (i'm calling close on the SQL Connection here, when the thread
is finished)

After analyzing it a bit I understand the pool wants to destroy the object
because my pool can not support any more idle connection (I'm at the point
where active=maxActive=maxIdle=5).
What I do not understand is why the destroyObject method does:

public void destroyObject(Object key, Object obj) throws Exception {
       if (obj instanceof PooledConnectionAndInfo) {
           PooledConnection pc =
((PooledConnectionAndInfo)obj).getPooledConnection();
           pcMap.remove(pc);
           pc.close();
       }
   }

Which means it removes the mapping and close the PooledConnection. At this
point, the listener is still active and it calls the listener which will
obviously fail:

public void connectionClosed(ConnectionEvent event) {
       PooledConnection pc = (PooledConnection)event.getSource();
       // if this event occured becase we were validating, ignore it
       // otherwise return the connection to the pool.
       if (!validatingMap.containsKey(pc)) {
           PooledConnectionAndInfo info =
               (PooledConnectionAndInfo) pcMap.get(pc);
           if (info == null) {
               throw new IllegalStateException(NO_KEY_MESSAGE);   //
<--------- the Exception which is thrown
           }



> Improvement of error recovery in KeyedCPDSConnectionFactory
> -----------------------------------------------------------
>
>                 Key: DBCP-216
>                 URL: https://issues.apache.org/jira/browse/DBCP-216
>             Project: Commons Dbcp
>          Issue Type: Improvement
>    Affects Versions: 1.2.2
>         Environment: Windows XP, Java 1.5.0_06-b05, Sybase ASE 12.5.4, jConnect 6.0.5
EBF 13862, Commons Pool 1.3
>            Reporter: Marcos Sanz
>             Fix For: 1.3
>
>         Attachments: KeyedCPDSConnectionFactory.java.diff
>
>
> Attached you'll find a patch that improves the recovery of the class in different error
situations.
> 1. The addition of removeConnectionEventListener() in destroyObject() ensures that the
listener is removed, which is not guaranteed to have happened upon call of destroyObject().
We are for sure not interested any more in events, since we are about to destroy.
> 2. The same addition is made to connectionClosed(). Additionally, we have substituted
there the call to destroyObject() with a call to pool.invalidateObject(). This is necessary
because otherwise the object is destroyed but not removed from the pool.
> 3. The same substitution is made in connectionErrorOccurred(), otherwise the object might
remain in the pool.

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