Not sure if this is a leak or something else, but usually i had similar issues because of low JVM memory before. 3.9.1 was running fine for a month. I have upgraded to 3.9.3 6 days ago. Today all clients were disconnected and i had to reboot the server. Admin Console was also unavailable. Can't say now what the problem was. Will watch JVM memory now.
On a side note. Logs are still not working for me (all log files a zero KB). Thought Daryl has fixed this with https://igniterealtime.org/issues/browse/OF-640