After ODM upgrade, we observed that the decision service war file was undeployed and redeployed, Were there any known ODM bugs or issues that can cause the tomcat to redeploy the war files?

Please make sure autodeploy is set to false in tomcat's server.xml:

<host ... autodeploy="false" ...

With autodeploy turned on (the default setting), Tomcat will check on a regular basis if the files of your application have changed on disk, and redeploy the application if they did. As checking if files have changed is cpu and memory intensive, it is recommend to disable the automatic web application

redeployment feature on production servers, especially if your have large rulesets, as the ruleset caching can take a long time.

This is a tomcat feature, so why it thinks the ODM decision service webapp has changed and thus needs redeploy is out of our control. It might be due to disk instability as discussed in this thread:

https://stackoverflow.com/questions/53745188/tomcat-undeploys-wars-automatically-after-some-time

or some other reasons. ODM is just web applications running on top of tomcat, and the redeploy is not triggered by the application.

You can also monitor to see if the ODM decision service.war in tomcat's webapps location does change and thus cause the redeployment.