Very good question. Please be aware that Log4j will *not* clear the 
ThreadContext. Your concern that ThreadContext values may become visible to 
other threads because of Tomcat’s thread pool is a legitimate concern. 

It is a good idea to explicitly clear values when the application is done with 
them. The CloseableThreadContext can be useful here. 


(Shameless plug) Every java main() method deserves

> On Apr 17, 2018, at 11:01, Kevin Jung <> wrote:
> Hello,
> I am using Log4j 2 ThreadContext with Tomcat.  I wonder if I need to clear
> ThreadContext at the end (or start) of HTTP request in order to avoid the
> context data being carried over to next HTTP request processing.
> I was assuming that thread context is cleared when Tomcat thread is put
> back in the thread pool and when a Tomcat thread starts processing new HTTP
> request, it starts with an empty thread context, nothing carried over from
> the previous HTTP request.  But that's my assumption, I want to make sure I
> do not need to clear at the end, like using a servlet filter.  Or should I
> use CloseableThreadContext to avoid carrying over among HTTP requests?
> Thanks,
> Kevin

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