Re: Memory Leak Issue with Symlinked WAR Files and autoDeploy

On 25/11/2025 04:14, Harshit Sharma wrote:

What Chuck said, Plus...

<snip/>

>     Questions for the Community
> 
>  1.
> 
>     Is our symlink-based deployment approach with
>     autoDeploy="true"causing classloader leaks??

No.

>  2.
> 
>     What is the recommended deployment strategy for production
>     environments to avoid memory leaks when updating WAR files??

Don't deploy applications with memory leaks. This is an application 
problem, not a Tomcat problem.

>  3.
> 
>     Are there known issues with Tomcat 7.0.41 related to classloader
>     leaks during redeployment??

Not that match your description of a leak every reload (there are a 
couple where you might see a leak on the first but not subsequent reloads).

There have been multiple improvements to Tomcat's 
JreMemoryLeakPreventionListener since 7.0.41 which helps prevent memory 
leaks due to the application's use of various parts of the JRE.

>  4.
> 
>     What monitoring or preventive measures can we implement to detect
>     and mitigate this issue before it causes production outages??

Update to a supported version of Tomcat. The latest 9.0.x release will 
be the minimum work since it still supports Java EE. Be sure to read the 
migration guides:

https://tomcat.apache.org/migration.html

There is at least one commercial vendor that offers support for Tomcat 7 
but even then the supported version is based on 7.0.109 so you'd have a 
significant update to do anyway. I doubt updating to 9.0.x would be much 
more effort.

> We suspect the combination of symlinked WAR files, autoDeploy="true", 
> and no-restart deployments is preventing proper cleanup of old 
> classloaders, but we'd like to understand the root cause and implement a 
> robust solution.

Those suspicions are very likely wrong.

> Any insights, best practices, or references to similar issues would be 
> greatly appreciated.

https://tomcat.apache.org/presentations/2010-08-05-javaone-Memory-Leaks-60mins.pdf

Mark