Unmanaged Thread Problem - WebSphere Compliant Spring Task Schedulers - (JNDI Context problems)

Problems Summary

1. Spring creates a separate threads to handle schedulers , but most of J2EE container vendors like websphere , weblogic ..etc doesn't support the threads created outside of containers. (These are threads called unmanaged threads)
2. Following exception was thrown when we try to lookup the objects directly using javax.naming.initialContext . (We have JAX-RPC webservices client code that is generated by RAD using WSDL , which is auto generated code has the direct initial context lookups)

Exception Occured

  javax.naming.ConfigurationException: A JNDI operation on a "java:" name cannot be completed because the server runtime is not able to associate the operation's thread with any J2EE application component.  This condition can occur when the JNDI client using the "java:" name is not executed on the thread of a server application request.  Make sure that a J2EE application does not execute JNDI operations on "java:" names within static code blocks or in threads created by that J2EE application.  Such code does not necessarily run on the thread of a server application request and therefore is not supported by JNDI operations on "java:" names. [Root exception is javax.naming.NameNotFoundException: Name "com/env/url/testrouce"

Explanation and solution

IBM clearly states that don't create unmanaged threads (this is true with most of J2EE container vendors), for the following reasons:

1. The application server does not recognize unmanaged threads.
2. Unmanaged threads do not have access to Java EE contextual information.
3. Unmanaged threads can use resources without being monitored by the application server.
4. Unmanaged threads can adversely affect application server functions such as shutting down gracefully or recovering resources from failure.
5. An administrator cannot control the number of unmanaged threads or their use of resources.

http://pic.dhe.ibm.com/infocenter/wasinfo/v7r0/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/cspr_design.html

Spring Framework Support

Spring framework does provide a package with scheduling classes based on CommonJ WorkManager/TimerManager that supported by IBM Websphere 6.0+ and BEA weblogic 9.0+.  Spring Commonj classes link is provided in references section.

Steps to create websphere compliant task scheduler

1. Create a task (That implements the runnable interface)
2. Add the Websphere timer Manager reference in the web.xml and ibm-web-bnd.xmi
3. Configure task at specific intervals in the SpringContext.xml

Step1: Create task

public class TestTask implements Runnable {

public void run() {

//your work to be executed        

}

}

Step 2: add websphere timer manager references in project

In Web.xml

<resource-ref>

<description>TimerManager</description >

<res-ref-name>timerManager</res-ref-name >

<res-type>commonj.timers.TimerManager</res-type >

<res-auth>Container</res-auth >

<res-sharing-scope>Unshareable</res-sharing-scope >

</resource-ref>

in ibm-web-bnd.xml

<resource-ref name="timerManager" binding-name="tm/default" ></resource-ref>

Step 3: configure scheduler

<bean id="testTask" class="com.sivavaka.test.spring.scheduler.TestTask">

</bean>        

<bean id= "timerScheduler" class="org.springframework.scheduling.commonj.TimerManagerTaskScheduler" >

      <property name="resourceRef" value="true"/>

      <property name="timerManagerName" value="timerManager"/>

</bean>

<!-- To schedule job for every one hour then cron will be "0 0 0/1 * * ?" -->

<!-- Websphere Compliant Thread :: Runs for every 5 mins -->         

<task:scheduled-tasks scheduler="timerScheduler" >

      <task:scheduled ref="testTask" method="run" cron="0 0/5 * * * ?" />

</task:scheduled-tasks >

If you create the scheduler like above , you can see the WebSphere Runtime available to thread that executes this task , basically it is WebSphere managed thread

  

But if you use the Spring's task scheduler directly (I mean without using the websphere timemanager), thread that executes this task doesn't have access the Websphere Runtime causing the J2EE container services are not available.

References

1. http://pic.dhe.ibm.com/infocenter/wasinfo/v7r0/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/cspr_design.html
2. Workmanagers (http://pic.dhe.ibm.com/infocenter/wasinfo/v8r0/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/asyncbns/concepts/casb_workmgr.html)
3. http://docs.spring.io/spring/docs/3.0.x/api/org/springframework/scheduling/commonj/package-summary.html

Download/Browse the Sample Code

1. To download sample code war file  (https://sourceforge.net/projects/blog-sivavaka-com-code-samples/files/WebSphere%20Compliant%20Spring%20Task%20Scheduler/)
2. To browser the sample code (https://code.google.com/p/blog-sivavaka-com-code-samples/source/browse/#svn%2Ftrunk%2FSivaTestSpringScheduler)