log4j has a potential memory leak

SEVERE: A web application created a ThreadLocal with key of type [org.apache.log4j.helpers.ThreadLocalMap] (value [org.apache.log4j.
helpers.ThreadLocalMap@28285ae4]) and a value of type [java.util.Hashtable] (value [{}]) but failed to remove it when the web applic
ation was stopped. To prevent a memory leak, the ThreadLocal has been forcibly removed.

http://stackoverflow.com/questions/16096685/how-to-solve-log4j-causing-a-memory-leak

Looks like we need to upgrade that…