[pgpool-committers: 7810] pgpool: Fix orphan process is left when pgpool is going down.

[Tatsuo Ishii]

Fix orphan process is left when pgpool is going down.

When pgpool is going down while follow primary command is ongoing,
some process started by follow primary child process could be left.
The follow primary child calls trigger_failover_command() to run the
follow primary script by using system(3). Unfortunately the process
started by system(3) was not tracked by anyone and it was possible
that the process(es) are left. To reproduce the problem you can edit
the test script (test,sh) for the regression test
075.detach_primary_left_down to change the timeout counter to small
number, say 1. i.e.,
change:
cnt=60
to
cnt=1

To fix the problem, the follow primary child process calls setsid(2)
to set new session id. When Pgpool-II main goes down, the exit handler
kills all the process including the process started by system(3), by
specifying kill(-(follow primary child process pid)).

Also in the initialization of the follow primary process, unmask
signals and assign default behavior to each signal (this should have
been done much earlier).

Branch
------
V4_1_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=4a012f8e0053914f560481fb5b4d64e1a70dcfd7

Modified Files
--------------
src/main/pgpool_main.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 62 insertions(+), 5 deletions(-)