Confirmed occurrence on Zentyal 4.1, SOGo 2.3.1, after en masse switch to sogo webmail usage
in /var/log/sogo/sogo.log memory-hungry process PID's logs
Sep 14 11:07:34 sogod [8883]: 192.168.106.2 "GET /SOGo/ HTTP/1.1" 200 4281/0 0.036 11290 62% -748K
Sep 14 11:07:39 sogod [8883]: <0x0x7ff663705cf8[NGImap4Client]> Note: no key found for sorting, using 'DATE': (null)
Sep 14 11:08:38 sogod [5475]: [WARN] <0x0x7ff662ed87b8[WOWatchDogChild]> pid 8883 has been hanging in the same request for 1 minutes
Sep 14 11:09:38 sogod [5475]: [WARN] <0x0x7ff662ed87b8[WOWatchDogChild]> pid 8883 has been hanging in the same request for 2 minutes
and the warning about hangup repeats every minute. This happened for every client (web interface mostly) that was rejected with
"No child available to handle incoming request!". For me it was not related to user profile, it seems.
I've implemented a solution from this thread (20 workers in the stub sogo.mas), everything seems to be back to normal now. You really got me out of a pickle.
An amusing desperate measure:
To keep the server alive, I kept killing those frozen processes
tail -f /var/log/sogo/sogo.log | grep --line-buffered "1 minute" | sed -u 's/^.*pid\ //' | sed -u 's/\ .*//' | while read proces; do kill -9 $proces; echo -n "Delikvent: "$proces" " ; date ; done