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Ankit,

On 10/10/19 10:17, ankitr.de...@spec-india.com wrote:
> We are using Tomcat 7.0.94 version and we have facing memory
> leakage issue when tomcat server is going to shutdown.
>
> Please help in this case, how to solve these kind of logs?
>
> Please find below sample logs from catalina.log file and code.
>
>
>
> Oct 10, 2019 6:35:36 PM
> org.apache.catalina.loader.WebappClassLoaderBase
> clearReferencesThreads
>
> SEVERE: The web application [/TLSAdmin] appears to have started a
> thread named [Timer-0] but has failed to stop it. This is very
> likely to create a memory leak.

Your application started this thread and hasn't stopped it. (See below)

> Oct 10, 2019 6:35:36 PM
> org.apache.catalina.loader.WebappClassLoaderBase
> clearReferencesThreads
>
> SEVERE: The web application [/TLSAdmin] appears to have started a
> thread named [schedulerFactory_Worker-1] but has failed to stop it.
> This is very likely to create a memory leak.

Same here, except it's likely to be a thread pool with a number of
threads with similar names.

To fix the thread issues, you need to find the place in your code
where the threads are started (or the threadpool is created) and make
sure that you have access to that thread (or pool) during application
shutdown. Storing stuff like this in the application (context) scope
is one way to do it.

I would recommend another ServletContextListener that locates those
threads (pools) and stops them. Remember that Thread.stop() doesn't
really work. Instead, you have to let the thread know that it's time
to stop itself.

Threads called "Timer-X" are usually simple threads created by
java.util.TimerTask and friends, and you should be able to store a
reference to the task and stop it on app shutdown.

> [snip]

> Oct 10, 2019 6:35:36 PM
> org.apache.catalina.loader.WebappClassLoaderBase
> checkThreadLocalMapForLeaks
>
> SEVERE: The web application [/TLSAdmin] created a ThreadLocal with
> key of type [java.lang.ThreadLocal] (value
> [java.lang.ThreadLocal@794fa987]) and a value of type
> [flex.messaging.config.SystemSettings] (value
> [flex.messaging.config.SystemSettings@7dca495e]) but failed to
> remove it when the web application was stopped. Threads are going
> to be renewed over time to try and avoid a probable memory leak.

Something in "flex" has put an object in ThreadLocal storage and never
removed it. This is harder to fix than the threading stuff because you
each thread needs to purge the ThreadLocal objects in order to "clean"
the system.

You have two options, really:

1. Allow Tomcat to clear these references, and otherwise ignore the
error messages.

2. Change your application so that at the end of each request you
remove these ThreadLocal values from the request-processing thread.

Hope that helps,
- -chris
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