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Message-ID: <42138167.9060803@surfeu.fi>
Date: Wed, 16 Feb 2005 19:22:47 +0200
From: Ilkka Priha <impriha@surfeu.fi>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Closed connections in pool
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Hello

We noticed that under heavy load (lack of memory) OJB returns closed Connections 
into the pool. This happens when the finalizer activates the finalize method of 
PersistenceBroker instances. At least MySQL Connections are already closed at 
this point (their finalize called as well?). Closed Connections cause a lot of 
trouble later on when borrowed back to use from the pool.

System Thread [Finalizer] (Suspended (breakpoint at line 61 in
     ConnectionFactoryPooledImpl))
ConnectionFactoryPooledImpl.returnConnectionToPool(JdbcConnectionDescriptor,
     Connection) line: 61
ConnectionFactoryPooledImpl(ConnectionFactoryAbstractImpl).releaseConnection(
     JdbcConnectionDescriptor, Connection) line: 90
ConnectionManagerImpl.releaseConnection() line: 314
PersistenceBrokerImpl.close() line: 336
PersistenceBrokerImpl.finalize() line: 1946
Finalizer.invokeFinalizeMethod(Object) line: not available [native method]
Finalizer.runFinalizer() line: 83
Finalizer.access$100(Finalizer) line: 14
Finalizer$FinalizerThread.run() line: 160

We added a simple check to an extended version of the 
ConnectionFactoryPooledImpl, which fixes the problem and could be applied to the 
original version, too.

-- Ilkka

     public void returnConnectionToPool(JdbcConnectionDescriptor jcd,
         Connection con) throws LookupException
     {
         try
         {
             if (!con.isClosed())
             {
                 super.returnConnectionToPool(jcd, con);
             }
         }
         catch (LookupException x)
         {
             throw x;
         }
         catch (Exception x)
         {
             throw new LookupException(x);
         }
     }

     public Connection getConnectionFromPool(JdbcConnectionDescriptor jcd)
         throws LookupException
     {
         try
         {
             Connection con;
             do
             {
                 con = super.getConnectionFromPool(jcd);
             } while (con.isClosed());

             return con;
         }
         catch (LookupException x)
         {
             throw x;
         }
         catch (Exception x)
         {
             throw new LookupException(x);
         }
     }


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