[PATCH] initialize signal handlers before writing pid file
Iñaki Baz Castillo
ibc at aliax.net
Wed Jan 20 03:45:33 EST 2010
El Miércoles, 20 de Enero de 2010, Eric Wong escribió:
> This prevents trigger-happy init scripts from reading the pid
> file (and thus sending signals) to a not-fully initialized
> master process to handle them.
> This does NOT fix anything if other processes are sending
> signals prematurely without relying on the presence of the pid
> file. It's not possible to prevent all cases of this in one
> process, even in a purely C application, so we won't bother
> We continue to always defer signal handling to the main loop
> anyways, and signals sent to the master process will be
> deferred/ignored until Unicorn::HttpServer#join is run.
Hi Eric, I've already tested it. It works great :)
To check it I use the following init script "reload" action which hope could
be useful for others (it requires loading "/lib/lsb/init-functions"):
# 0 if daemon has been reloaded
# 1 if daemon was not running
# 1 if daemon could not be reloaded
log_daemon_msg "Safe reloading $DESC"
oldpid=$(pidofproc -p $PIDFILE)
if [ "$oldpid" ] ; then
kill -s USR2 $oldpid
log_action_msg "signal USR2 sent to $NAME master process (pid $oldpid) to
fork a new master and workers processes"
log_action_msg "waiting for the new process to successfully start..."
while [ "$(pidofproc -p $PIDFILE.oldbin)" ]; do
newpid=$(pidofproc -p $PIDFILE)
# If the PID has definitively changed than the new master is running.
if [ "$oldpid" != "$newpid" ] ; then
log_success_msg "server correctly reloaded, new master process has pid
# If not, the new master process couldn't start due to the new
# configuration or code error.
log_failure_msg "error running a new master process, $NAME was not
reloaded (check error log)"
log_failure_msg "$NAME is not running"
And I test the following loop to check it:
while [ 0 ] ; do /etc/init.d/myserver reload ; done
Iñaki Baz Castillo <ibc at aliax.net>
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