Project Jigsaw, Apache Tomcat and RMI related memory leaks

[Alan Bateman]

On 18/04/2016 10:18, Mark Thomas wrote:
> Hi,
>
> The Apache Tomcat community was asked by Rory O'Donnell for feedback on
> JDK 9 + Project Jigsaw. Having provided that feedback we were directed
> here so I have reproduced that feedback below.
>
>
> I've started testing Tomcat trunk with JDK 9 + Project Jigsaw and it
> looks like we are going to hit a bunch of problems related to Tomcat's
> memory leak protection.
>
> The short version is there are lots of JDK calls that can result in a
> reference being retained to the current class loader. If that class
> loader is the web application class loader it often ends up being pinned
> in memory. This triggers a memory leak when the web application is
> reloaded since the web application class loader is not eligible for GC.
>
> Tomcat generally uses reflection to find these problems. It then does
> one of two things:
> - If the JRE provides an API the application developer should have used
> to clean up the reference, Tomcat does this for them and then logs a
> very loud error message telling the developer they need to fix their app.
> - If there is nothing the developer could have done to avoid the
> problem, Tomcat cleans it up. Usually this is via reflection again.
>
> Reporting this second class of issues as JRE bugs has been on my TODO
> list for a long time. It looks like Java 9 is going to bump this to the
> top of the list.
I remember you brought this up on core-libs-dev [1] and the suggestion 
at the time was to create bugs for any of the issues that are still 
relevant. So yes, bumping the priority on that would be good.

On the RMI issue then it would be good to start a thread specifically on 
this topic on core-libs-dev.

-Alan

[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-September/028823.html