if TimedRotatingFileHandler does an doRollover() it opens the new file hardcoded with mode "w" whilst the baseclass FileHandler opens it with mode "a" if nothing else is specified in the constructor. it should use the same default behavior as FileHandler and/or give a way to specify another open-mode.

if multiple processes write to the same file, and one does the RollOver all other newly spawned processes write to the end of the new file but the still running first process who did the rollover will write from the beginning of the file - overwriting log entries from the other procs...