Comment 4 for bug 1809823

UPDATE:
to reproduce the bug:
log into the neutron_api container :

docker exec -it --user root neutron_api bash
ps fax| grep neutron_api
()[root@undercloud /]# ps fax
  PID TTY STAT TIME COMMAND
  115 ? Ss 0:00 bash
  140 ? S+ 0:00 \_ top
   44 ? Ss 0:00 bash
  241 ? R+ 0:00 \_ ps fax
    1 ? Ss 0:00 /usr/local/bin/dumb-init /bin/bash /usr/local/bin/kolla_sta
    7 ? Ss 0:05 /usr/bin/python2 /usr/bin/neutron-server --config-file /usr
   27 ? S 0:08 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file
   28 ? S 0:00 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file
   29 ? S 0:03 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file
   30 ? S 0:03 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file
   31 ? S 0:03 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file
   32 ? R 5:27 \_ /usr/bin/python2 /usr/bin/neutron-server --config-file

Kill the last on pid ( 32 ) with sigup-
kill -1 32

check the server.log after few seconds :
2018-12-26 00:00:36.077 40997 ERROR oslo_service.service [-] Error starting thread.: RuntimeError: A fixed interval looping call can only run one function at a time

in our environment, this occurs without someone issuing kill -1 , but just after 4 days more or less there's a sigup and docker becomes unhealthy.