[pgpool-general: 4836] failover_command and follow_command does not exit and hangs indefinitely

[Tema Zelikin]

Hello.

I'm trying to configure expandable cluster using Ubuntu 14.04 LTS,
PostgreSQL 9.5 and PgPool 3.5.3.
I'm having a problem with failover/follow commands: any command, be that
ansible-playbook, ssh or anything else does not exit after successful
run and hangs indefinitely, reacting only to "kill -9".  Which, in case
of failover script, makes pgpool running that command wait for it's exit
and also to hang.
My current workaround is forking script, running a command in the new
fork, and terminate it after successful execution. Obviously, its not a
viable production solution.
Please help me undestand, why is this happening?