在/etc/init.d脚本中对守护程序的调用被阻止，未在后台运行 [英] Call to daemon in a /etc/init.d script is blocking, not running in background

问题描述

我有一个要守护的Perl脚本.基本上，此perl脚本将每30秒读取一个目录，读取其找到的文件，然后处理数据.为了简单起见，请考虑以下Perl脚本(称为synpipe_server，该脚本在/usr/sbin/中有符号链接):

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;
}

因此，此脚本基本上每3秒打印一次内容.

So this script basically prints something every 3 seconds.

然后，因为我想守护该脚本，所以我也将此bash脚本(也称为synpipe_server)放在/etc/init.d/中:

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

因此，(如果我很了解守护程序的文档)Perl脚本应该在后台运行，并且如果执行，输出应该重定向到/dev/null.

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

但这是我得到的:

[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]# 

因此，它启动了Perl脚本，但是运行了它，而没有将其与当前的终端会话分离，因此我可以在控制台中看到输出的输出……这并不是我真正期望的.此外，PID文件为空(或仅带有换行符，守护程序没有返回pid).

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).

有人知道我在做什么错吗?

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

也许我应该说我在Red Hat机器上.

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

Scientific Linux SL release 5.4 (Boron)

谢谢， 托尼

推荐答案

我终于在bash初始化脚本中重新编写了start函数，并且我不再使用daemon.

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
}

我检查pid文件是否不存在(如果存在，请写警告).如果没有，我使用

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 &

启动脚本.

我不知道这种方法是否安全(?)，但可以使用.

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

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