in reply to Running multiple instances of a daemon simultaneously?

Trenin:

I just reviewed the docs for Proc::Daemon and don't see where the difficulty lies in running multiple instances. What's giving you the problem?

As you mention, the code in the link provided does want to use a single daemon, though it doesn't look like it would be all that difficult to modify. To do so, I'd suggest adding a PID command line argument to tell the daemons apart, and make sure the run function displays the pid of the new daemon. Finally, if the PID argument passed in was 0 or LIST or some such, it would just list all matching daemons.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

  • Comment on Re: Running multiple instances of a daemon simultaneously?

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Re^2: Running multiple instances of a daemon simultaneously?
by Trenin (Initiate) on Aug 07, 2014 at 17:03 UTC

    Yeah I guess I just wasn't firing on all cylinders yesterday; I'm not sure why I couldn't get it to work. I've run into a slightly different issue: the daemon doesn't return input control to the user. So for example the behavior of the script I borrowed from is:

    [user@linux ~] perl original.pl --start

    Starting...

    [user@linux ~]

    But my version hangs, like

    [user@linux ~] perl original.pl --start

    Starting...

    and I have to ctrl-z before I can enter anything else

    Here's my modified example daemon:

    #!/usr/bin/perl
use warnings;
use strict;
use Getopt::Long;
use Proc::Daemon;
use Cwd;
use File::Spec::Functions;

my $daemon = Proc::Daemon->new(
    work_dir => getcwd()    
);

my $pid;
my $daemonize = 1;

GetOptions(
    'daemon!'    => \$daemonize,
    "start"     => \&run,
    "status"     => \&status,
    "stop"         => \&stop
);

sub stop{
    if($pid){
        print "Stopping pid $pid... \n";
        if($daemon->Kill_Daemon($pid)){
            print "Successfully stopped. \n";
        }else{
            print "Could not find $pid. Was it running? \n";
        }
    }else{
        print "not Running, nothing to stop. \n";
    }
}

sub status{
    if($pid){
        print "Running with pid $pid. \n";
    }else{
        print "Not running. \n";
    }
}

sub run{
    if (!$pid){
        print "Starting...\n";
        if($daemonize){
            $pid = $daemon->Init;
    
        }
        while(1){
            open(my $FH, '>>', catfile(getcwd(), "log.txt"));
            print $FH "Logging from PID $pid at " . time() . "\n";
            close $FH;
            sleep 5;
        }
    }else{
        print "No active daemons. \n";
    }
}

    [download]
    I've narrowed the problem down to the assignment $pid = $daemon->Init;

    But removing the assignment obviously means the pid isn't stored. I guess I could just go with command line arguments.

    EDIT: OR I could write a temp pid file, write to and then read from the file, and then destroy it.

[reply]
[d/l]
[select]

      Trenin:

      Are you certain that it's $daemon->Init? The reason I ask is that immediately after doing that you enter an infinite loop, so I wouldn't expect you to get control again until you either put the job in the background or terminate it.

      ...roboticus

      When your only tool is a hammer, all problems look like your thumb.

[reply]
[d/l]
        Sorry for the late reply. It did work for me; the job immediately goes into the background, and I can terminate it by killing the PID.
[reply]

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