Ejb preinvoke errors, db disconnects after long periods of inactivity

Question

Hi,
I have a basic 3-tier ee app
-mysql 4.0 db on linux (with mySql's newest stable jdbc driver)
-Sun AS 7.02 SE on Linux (rh9), running a J2EE application consisting of :
-a number of entity beans
-one stateless session bean (facade for entity beans)
-a web-service exposing business methods on the session bean
-jsp-based test-client
-kSOAP-based personalJava client
I noticed that if the service is idle for more than 10-12 hours, then upon invoking any call from either of the clients i get the following server error:
[05/Mar/2004:09:37:21] INFO ( 4865):      CORE3282: stdout: Trace: TrainerClientsSessionBean.getAllClients() //remote method request successfully got to the session bean
[05/Mar/2004:09:37:21] INFO ( 4865):      CORE3282: stdout: Error in user method 'getAllClients'
[05/Mar/2004:09:37:21] INFO ( 4865):      CORE3282: stdout: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
[05/Mar/2004:09:37:21] INFO ( 4865):      CORE3282: stdout: java.rmi.RemoteException: Exception thrown from bean; nested exception is: java.lang.RuntimeException: Got exception during XAResource.start:
and a little lower in log file.....
[05/Mar/2004:09:37:21] WARNING ( 4999):      
[NRU-package.WIQwsGenServer.WIQwsRPCBean.2]: Invalid sessionID: 133
[05/Mar/2004:09:37:21] SEVERE ( 4999):      EJB5017: Exception while running preinvoke : ejbName = [WIQws]
[05/Mar/2004:09:37:21] SEVERE ( 4999):      
     javax.ejb.NoSuchObjectLocalException: The EJB does not exist.
     at com.sun.ejb.containers.StatefulSessionContainer.getContext(StatefulSessionContainer.java:720)
Also, I have a dbping utility installed as service on this AS. The utility allows me to ping a datasource (for example one that above app uses). When trying to ping it immediately after getting the above exception i get:
SQLException is :Communication link afailure: java.io.IOException, underlying cause: Unexpected end of input stream
** BEGIN NESTED EXCEPTION **
java.io.IOException
MESSAGE: Unexpected end of input stream
java.io.IOException: Unexpected end of input stream
     at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:1455)
     at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:1826)
     at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1098)
     at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1192)
     at com.mysql.jdbc.MysqlIO.sqlQuery(MysqlIO.java:1153)
     at com.mysql.jdbc.Connection.execSQL(Connection.java:2048) .......
This is my first j2ee app, so i accepted all default bean config settings. Is the problem I'm having:
- a jdbc driver problem: driver allows as to disconnect from db if inactive for a long time, hence the preinvoke errors.
- a bean (stateless or entity?) configuration problem: despite having a pool of 8 beans, which i understand are to be active at all times, a bean is passivated without appserver's "bean dispatcher" (my term) knowing about it. The bean dispatcher then tries to access a passivated/destroyed version of bean and gets a preinvoke error
-both of the above
-some other problem?
I would appreciate any insight and hints to solution(s), or solutions themselves :)
thanks,
-nikita

Answer 1

Make sure that you use connection validation on your connection pool and see if that solves it.