tony tony - 3 months ago 16
Linux Question

Call to daemon in a /etc/init.d script is blocking, not running in background

I have a Perl script that I want to daemonize. Basically this perl script will read a directory every 30 seconds, read the files that it finds and then process the data. To keep it simple here consider the following Perl script (called synpipe_server, there is a symbolic link of this script in

/usr/sbin/
) :

#!/usr/bin/perl
use strict;
use warnings;

my $continue = 1;
$SIG{'TERM'} = sub { $continue = 0; print "Caught TERM signal\n"; };
$SIG{'INT'} = sub { $continue = 0; print "Caught INT signal\n"; };

my $i = 0;
while ($continue) {
#do stuff
print "Hello, I am running " . ++$i . "\n";
sleep 3;
}


So this script basically prints something every 3 seconds.

Then, as I want to daemonize this script, I've also put this bash script (also called synpipe_server) in
/etc/init.d/
:

#!/bin/bash
# synpipe_server : This starts and stops synpipe_server
#
# chkconfig: 12345 12 88
# description: Monitors all production pipelines
# processname: synpipe_server
# pidfile: /var/run/synpipe_server.pid
# Source function library.
. /etc/rc.d/init.d/functions

pname="synpipe_server"
exe="/usr/sbin/synpipe_server"
pidfile="/var/run/${pname}.pid"
lockfile="/var/lock/subsys/${pname}"

[ -x $exe ] || exit 0

RETVAL=0

start() {
echo -n "Starting $pname : "
daemon ${exe}
RETVAL=$?
PID=$!
echo
[ $RETVAL -eq 0 ] && touch ${lockfile}
echo $PID > ${pidfile}
}

stop() {
echo -n "Shutting down $pname : "
killproc ${exe}
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
rm -f ${lockfile}
rm -f ${pidfile}
fi
}

restart() {
echo -n "Restarting $pname : "
stop
sleep 2
start
}

case "$1" in
start)
start
;;
stop)
stop
;;
status)
status ${pname}
;;
restart)
restart
;;
*)
echo "Usage: $0 {start|stop|status|restart}"
;; esac

exit 0


So, (if I have well understood the doc for daemon) the Perl script should run in the background and the output should be redirected to
/dev/null
if I execute :

service synpipe_server start


But here is what I get instead :

[root@master init.d]# service synpipe_server start
Starting synpipe_server : Hello, I am running 1
Hello, I am running 2
Hello, I am running 3
Hello, I am running 4
Caught INT signal
[ OK ]
[root@master init.d]#


So it starts the Perl script but runs it without detaching it from the current terminal session, and I can see the output printed in my console ... which is not really what I was expecting. Moreover, the PID file is empty (or with a line feed only, no pid returned by daemon).

Does anyone have any idea of what I am doing wrong ?

EDIT : maybe I should say that I am on a Red Hat machine.

Scientific Linux SL release 5.4 (Boron)


Thanks,
Tony

Answer

I finally re-wrote the start function in the bash init script, and I am not using daemon anymore.

start() {
    echo -n "Starting $pname : "
    #daemon ${exe} # Not working ...
    if [ -s ${pidfile} ]; then
       RETVAL=1
       echo -n "Already running !" && warning
       echo
    else
       nohup ${exe} >/dev/null 2>&1 &
       RETVAL=$?
       PID=$!
       [ $RETVAL -eq 0 ] && touch ${lockfile} && success || failure
       echo
       echo $PID > ${pidfile}
    fi
}

I check that the pid file is not existing already (if so, just write a warning). If not, I use

 nohup ${exe} >/dev/null 2>&1 &

to start the script.

I don't know if it is safe this way (?) but it works.