log4j has some heavy synchronization, which can sometimes lead to code blocking up to 30 seconds (see [1]).

Investigate whether we should switch to log42 [2]. Perhaps we can simply program against the API (30K) and not even ship the implementation ?

[1] https://issues.apache.org/bugzilla/show_bug.cgi?id=51047

[2] http://logging.apache.org/log4j/2.x/