HI Christopher,

Thanks for you valuable reply, 

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

Can you please let us know how to Allow Tomcat to clear these references?


--Ankit

-----Original Message-----
From: Christopher Schultz <ch...@christopherschultz.net> 
Sent: 10 October 2019 11:08 PM
To: users@tomcat.apache.org
Subject: Re: Memory Leakage Problem in Tomcat 7.0.94

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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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