Tomcat not Shutting Down Completely (Tomcat 9.0.31)

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We are in the process of migrating our application from Websphere to Tomcat. One thing I have noticed is that when I issue the shutdown.sh for Tomcat, the process still keeps running. Initially I thought the process would end itself in a minute or two, but even after 5 minutes I still see the process alive. So I have to kill the process using kill -9 and then go for a start.

While shutting down I do see a lot of errors getting thrown on the console like:

org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [some_application] appears to have started a thread named [Timer-0] but has failed to stop it.

The code consists of webapps which are made a mix of servlets, spring and a whole bunch of threads are started when the application boots up.

Is there something I can do configuration-wise that would take care of this? Or this needs some code-work to compensate for something that WebSphere provided out-of-the-box?

Best Answer

Issues like that is best handled from code.

Although you can use catalina.sh stop -force to terminate the Tomcat instance no matter what, the point here is that Tomcat thinks those threads are running for a reason, and terminating your threads might leave your application in an inconsistent state (if it is terminated halfway of writing something, for example).

If you know for a fact that no such thing could happen, use the -force switch when stopping Tomcat.

However, it is best to write the application to either mark the threads as daemons (by calling setDaemon(true) on the Thread instance), so they can be terminated whenever the VM exits, or (if the threads should not be killed at any time) register a shutdown hook by implementing ServletContextListener, and doing the shutdown chores in the contextDestroyed method. Here is a question on StackOverflow about installing a shutdown hook.

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