NAME

App::Daemon - Start an Application as a Daemon

SYNOPSIS

     # Program:
   use App::Daemon qw( daemonize );
   daemonize();

     # Then, in the shell:
 
     # start app in background
   $ app start

     # stop app
   $ app stop

     # start app in foreground (for testing)
   $ app -X

     # show if app is currently running
   $ app status

DESCRIPTION

App::Daemon helps running an application as a daemon. Along with the common features offered by similar modules on CPAN, it

• supports logging with Log4perl: In background mode, it logs to a logfile. In foreground mode, log messages go directly to the screen.

• detects if another instance is already running and ends itself automatically in this case.

• shows with the 'status' command if an instance is already running and which PID it has:

      ./my-app status
      Pid file:    /tmp/tt.pid
      Pid in file: 14914
      Running:     no
      Name match:  0

Actions

App::Daemon recognizes three different actions:

my-app start

will start up the daemon. "start" itself is optional, as this is the default action,

        $ ./my-app
        

will also run the 'start' action. If the -X option is given, the program is run in foreground mode for testing purposes.

stop

will find the daemon's PID in the pidfile and send it a kill signal. It won't verify if this actually shut down the daemon or if it's immune to the kill signal.

status

will print out diagnostics on what the status of the daemon is. Typically, the output look like this:

    Pid file:    /tmp/tt.pid
    Pid in file: 15562
    Running:     yes
    Name match:  1
        /usr/local/bin/perl -w test.pl

This indicates that the pidfile says that the daemon has PID 15562 and that a process with this PID is actually running at this moment. Also, a name grep on the process name in the process table results in 1 match, according to the output above.

Note that the name match is unreliable, as it just looks for a command line that looks approximately like the script itself. So if the script is test.pl, it will match lines like "perl -w test.pl" or "perl test.pl start", but unfortunately also lines like "vi test.pl".

If the process is no longer running, the status output might look like this instead:

    Pid file:    /tmp/tt.pid
    Pid in file: 14914
    Running:     no
    Name match:  0

Command line options

-X

Foreground mode. Log messages go to the screen.

-l logfile

Logfile to send Log4perl messages to in background mode. Defaults to /tmp/[appname].log.

-u as_user

User to run as if started as root. Defaults to 'nobody'.

-l4p l4p.conf

Path to Log4perl configuration file.

-p pidfile

Where to save the pid of the started process. Defaults to /tmp/[appname].pid.

Setting Parameters

Instead of setting paramteters like the logfile, the pidfile etc. from the command line, you can directly manipulate App::Daemon's global variables:

    use App::Daemon qw(daemonize);

    $App::Daemon::logfile    = "mylog.log";
    $App::Daemon::pidfile    = "mypid.log";
    $App::Daemon::l4p_conf   = "myconf.l4p";
    $App::Daemon::background = 1;
    $App::Daemon::as_user    = "nobody";

    use Log::Log4perl qw(:levels);
    $App::Daemon::loglevel   = $DEBUG;

    daemonize();

AUTHOR

Mike Schilli, cpan@perlmeister.com

COPYRIGHT AND LICENSE

Copyright (C) 2008 by Mike Schilli

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.5 or, at your option, any later version of Perl 5 you may have available.