[CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
Hello fellow CentOS sysadmins,
I run a small multiplayer card game
with around 500 users at peak times.
The client is in Flash and the server is in Perl.
The Perl server binds to port 8080, i.e. only
1 instance of it can be started (important detail).
The Perl server poll()s TCP-sockets and forks
only once - at the startup by calling this method:
sub daemonize {
die Can not fork: $!\n unless defined (my $child = fork());
# the parent should die
exit 0 if $child;
setsid();
open(STDIN, '/dev/null');
open(STDOUT, '/tmp/pref.txt');
open(STDERR, 'STDOUT');
chdir('/');
umask(0);
}
It runs on CentOS 5.6 Linux / 64 bit,
PostgreSQL 8.4.8 and Perl 5.8.8.
Because my budget is small and I had enough
troubles already, I want to use as little additional
software as possible - so that I can change hosters
or reinstall my cheapo server quickly. That is why
I for example just log to /tmp/pref.txt instead of
installing syslog-ng. And that is why I'd like to
use /etc/inittab for restarting my Perl daemon.
My Perl daemon runs mostly stable, but
approx. once a week it can crash with a
May 29 11:06:46 myhost kernel: pref.pl[3113]:
segfault at 7fffa21e6fd8 rip 003cce274460
rsp 7fffa21e6fd0 error 6
Since I'm tired of restarting the server manually,
I've tried to add it to the /etc/inittab:
pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody
(and I've added a nightly cronjob to
pkill pref.pl in the hope to refresh perl this way).
Unfortunately this does not work as expected -
in the /var/log/messages I see that the script
is being started again and again every 5 mins:
Jun 2 18:55:56 myhost init: Id pref
respawning too fast: disabled for 5 minutes
What am I doing wrong here? I was hoping to
being able to use /etc/inittab here, because
I remember using it for a similar situation at work
few years ago (also with a Perl daemon)
and it worked well then...
Thank you!
Alex
P.S. I've also posted my question at
http://serverfault.com/questions/276428/restarting-a-perl-script-socket-daemon-from-etc-inittab
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Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
Alexander Farber wrote: Hello fellow CentOS sysadmins, I run a small multiplayer card game with around 500 users at peak times. The client is in Flash and the server is in Perl. snip My Perl daemon runs mostly stable, but approx. once a week it can crash with a May 29 11:06:46 myhost kernel: pref.pl[3113]: segfault at 7fffa21e6fd8 rip 003cce274460 rsp 7fffa21e6fd0 error 6 snip Ok, here's the more significant question: why's it SEGV'ing? What's at line 3113 that could segv? mark, was a programmer longer than I've been a sysadmin ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
On 6/2/2011 2:46 PM, Alexander Farber wrote:
The Perl server poll()s TCP-sockets and forks
only once - at the startup by calling this method:
sub daemonize {
die Can not fork: $!\n unless defined (my $child = fork());
# the parent should die
exit 0 if $child;
[]
Since I'm tired of restarting the server manually,
I've tried to add it to the /etc/inittab:
pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody
(and I've added a nightly cronjob to
pkill pref.pl in the hope to refresh perl this way).
Unfortunately this does not work as expected -
in the /var/log/messages I see that the script
is being started again and again every 5 mins:
Jun 2 18:55:56 myhost init: Id pref
respawning too fast: disabled for 5 minutes
What am I doing wrong here?
It needs to not fork/exit on its own if you want init to respawn when it
exits.
--
Les Mikesell
lesmikes...@gmail.com
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Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
On Thu, Jun 2, 2011 at 10:10 PM, Les Mikesell lesmikes...@gmail.com wrote:
On 6/2/2011 2:46 PM, Alexander Farber wrote:
The Perl server poll()s TCP-sockets and forks
only once - at the startup by calling this method:
sub daemonize {
die Can not fork: $!\n unless defined (my $child = fork());
# the parent should die
exit 0 if $child;
[]
Since I'm tired of restarting the server manually,
I've tried to add it to the /etc/inittab:
pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody
(and I've added a nightly cronjob to
pkill pref.pl in the hope to refresh perl this way).
Unfortunately this does not work as expected -
in the /var/log/messages I see that the script
is being started again and again every 5 mins:
Jun 2 18:55:56 myhost init: Id pref
respawning too fast: disabled for 5 minutes
What am I doing wrong here?
It needs to not fork/exit on its own if you want init to respawn when it
exits.
Thank you Les, so init does the forking for me?
I'll try it in few hours, when I have less users online.
And I wonder how often does init try to run
a program, before it stops for 5 minutes...
Mark, my pref.pl is 80 lines long, the rest is in few modules.
Yes, perl interpreter 5.8.8 crashes for me once a week,
but I don't really have a chance to solve it - I'm not a
perl interpreter developer myself, I don't have an easy
test case for them to try, I don't have a 2nd server or time
to reproduce it myself. I need to solve this problem now
(going to vacation on Sunday).
Greetings from Germany
Alex
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Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
I'll omit fork() and run my script from /etc/inittab as pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody 21 /tmp/pref.txt Do you think I still need setsid(); chdir(/); and umask(0); ? Regards Alex ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
2011/6/2 Alexander Farber alexander.far...@gmail.com:
On Thu, Jun 2, 2011 at 10:10 PM, Les Mikesell lesmikes...@gmail.com wrote:
On 6/2/2011 2:46 PM, Alexander Farber wrote:
The Perl server poll()s TCP-sockets and forks
only once - at the startup by calling this method:
sub daemonize {
die Can not fork: $!\n unless defined (my $child = fork());
# the parent should die
exit 0 if $child;
[]
Since I'm tired of restarting the server manually,
I've tried to add it to the /etc/inittab:
pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody
(and I've added a nightly cronjob to
pkill pref.pl in the hope to refresh perl this way).
Unfortunately this does not work as expected -
in the /var/log/messages I see that the script
is being started again and again every 5 mins:
Jun 2 18:55:56 myhost init: Id pref
respawning too fast: disabled for 5 minutes
What am I doing wrong here?
It needs to not fork/exit on its own if you want init to respawn when it
exits.
Thank you Les, so init does the forking for me?
I'll try it in few hours, when I have less users online.
And I wonder how often does init try to run
a program, before it stops for 5 minutes...
Mark, my pref.pl is 80 lines long, the rest is in few modules.
Yes, perl interpreter 5.8.8 crashes for me once a week,
but I don't really have a chance to solve it - I'm not a
perl interpreter developer myself, I don't have an easy
test case for them to try, I don't have a 2nd server or time
to reproduce it myself. I need to solve this problem now
(going to vacation on Sunday).
how about using monit to monitor/restart your perl server?
http://mmonit.com/monit/
--
Eero
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Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
On 6/2/2011 3:36 PM, Alexander Farber wrote: I'll omit fork() and run my script from /etc/inittab as pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl' nobody 21 /tmp/pref.txt Do you think I still need setsid(); chdir(/); and umask(0); ? Not sure about the setsid() - I think you want to stay in the same process group so init catches the sigchld and knows to respawn. Then again, init inherits orphan children to clean up their exit status anyway so maybe it doesn't matter. The rest affect the program behavior and should stay the same. -- Les Mikesell lesmikes...@gmail.com ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Restarting a Perl-script (socket daemon) from /etc/inittab
Thank you, now my perl daemon works with /etc/inittab I've removed fork() and used this line: pref:3:respawn:/bin/su -c '/usr/local/pref/pref.pl /tmp/pref.txt 21' nobody Regards Alex ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
