Problem with EJB and JMS - Failed to obtain/create connection

Question

hello ejb and jms programmers,
My problem is my topic MDB keep on retrieving the same message when there is a database connection failure. Maybe somebody could help me how to prevent to retrieve the same data?
Given:
- I purposedly turn off the pointbase database because im testing my error handling.
- Im using SJSAS 8 as my application server.
- My message Driven Bean of topic type.
- Im using CMP for my entity bean
Here is the scenario of whats happening - step by step:
1. A separate application publishes a message to JMS queue server
2. My MDB retrieves this message and do some processing then inserts a record (transaction history) in my database
3. But my db is turned off or down
4. My MDB sends a successful processing reply to the JMS queue server
5. Then i noticed that my server.log keeps on growing so when i opened it, the record was not inserted and printed the stacktrace below "RAR5117 : Failed to obtain/create connection. Reason : javax.transaction.SystemException" (complete stacktrace below)
6. I understand the cause of the stacktrace is because the DB is turned off. But what i dont understand is that my MDB keeps on reading the same message. Since my MDB is of topic type, isnt a topic MDB supposedly reads a message only once???
So my questions are:
1. how do i handle insert database error?
2. how can i stop my MDB from processing the same message?
3. any better suggestions?
Thank you in advance :)
leigh
*** more complete stack trace ***
[#|2005-01-09T15:35:57.097+0800|WARNING|sun-appserver-pe8.0.0_01|javax.enterprise.system.core.transaction|_ThreadID=17;|JTS5041: The resource manager is doing work outside a global transaction
javax.transaction.xa.XAException
     at com.pointbase.xa.xaException.getXAException(Unknown Source)
     at com.pointbase.xa.xaConnectionResource.start(Unknown Source)
     at com.sun.gjc.spi.XAResourceImpl.start(XAResourceImpl.java:162)
[#|2005-01-09T15:35:57.167+0800|SEVERE|sun-appserver-pe8.0.0_01|javax.enterprise.resource.resourceadapter|_ThreadID=17;|RAR5027:Unexpected exception in resource pooling
javax.transaction.SystemException
     at com.sun.jts.jta.TransactionImpl.enlistResource(TransactionImpl.java:185)
     at com.sun.enterprise.distributedtx.J2EETransaction.enlistResource(J2EETransaction.java:360)
     at com.sun.enterprise.distributedtx.J2EETransactionManagerImpl.enlistResource(J2EETransactionManagerImpl.java:303)
     at com.sun.enterprise.distributedtx.J2EETransactionManagerOpt.enlistResource(J2EETransactionManagerOpt.java:115)
[#|2005-01-09T15:35:57.177+0800|WARNING|sun-appserver-pe8.0.0_01|javax.enterprise.resource.resourceadapter|_ThreadID=17;|RAR5117 : Failed to obtain/create connection. Reason : javax.transaction.SystemException|#]
[#|2005-01-09T15:35:57.227+0800|WARNING|sun-appserver-pe8.0.0_01|javax.enterprise.resource.resourceadapter|_ThreadID=17;|RAR5114 : Error allocating connection : [Error in allocating a connection. Cause: javax.transaction.SystemException]|#]
[#|2005-01-09T15:35:57.237+0800|SEVERE|sun-appserver-pe8.0.0_01|javax.enterprise.system.container.ejb|_ThreadID=17;|EJB5071: Some remote or transactional roll back exception occurred
com.sun.jdo.api.persistence.support.JDODataStoreException: JDO77006: SQL exception: state = null, error code = 0.
NestedException: java.sql.SQLException: Error in allocating a connection. Cause: javax.transaction.SystemException
FailedObjectArray: [[email protected]5ac]
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.TransactionImpl.getConnectionInternal(TransactionImpl.java:1444)
     at com.sun.jdo.spi.persistence.support.sqlstore.impl.TransactionImpl.getConnection(TransactionImpl.java:1339)

Answer 1

Hi annie,
Wherever you are handling database transactions,
you'd not be able to create a Connection if database
is closed (I think you mentioned turning off the
database) then at this condition, you should
certainly throw a System level exception and stop all
processing with some meaningful flow to indicate a
failure (like display message on UI). Even
network problems are handled by exceptions... so I
don't see a reason why you didn't wrap it in the
first place.
Anyway, try handling specific exceptions rather than
the general Exception... this will give you a better
idea of what to do in case of an exception.Yes i know this. I am practicing this in my non-j2ee server applications. But the j2ee app im making, i just pass the db url in the descriptor and the app server automatically creates the connection for my app. So where would i put exception handling?
2. how can i stop my MDB from processing the same
message?Guaranteed delivery is not supposed to stop
processing. It will continue to process the message
after certain intervals till the message is
delivered. You shouldn't deliver it at all, if you
are able to detect that the database is off
The problem here is that my MDB automatically retrieves the message from the JMS queue server. Im not the one retrieving the messages manually.
My assumed behavior of topic MDB is once the a certain MDB retrieves a message it will not retrieve the same message anymore.
thank you in advance.
leigh