Re: Writing a Perl Daemon

Using Proc::PID_File and Proc::Daemon should get you most of the way there. Here is a chopped down version of a daemon script that I use, complete with logging. Hope it is a helpful starting point.

#!/usr/bin/perl

use strict;
use warnings;

use constant LOG_DIR    => '/var/log/mydaemon';
use constant LOG_FILE   => 'mydaemon.log';
use constant PIDDIR     => LOG_DIR;

use Proc::PID_File;
use Proc::Daemon;
use Log::Dispatch;
use Log::Dispatch::File;
use Date::Format;
use File::Spec;

sub dienice ($);

#
# fork and background process
#
our $ME = $0; $ME =~ s|.*/||;
our $PIDFILE = PIDDIR."/$ME.pid";
startDaemon();

#
# Setup a logging agent
#
our $HOSTNAME = `hostname`;
chomp $HOSTNAME;
my $log = new Log::Dispatch(
      callbacks => sub { my %h=@_; return Date::Format::time2str('%B %
+e %T', time)." ".$HOSTNAME." $0\[$$]: ".$h{message}."\n"; }
);
$log->add( Log::Dispatch::File->new( name      => 'file1',
                                     min_level => 'warning',
                                     mode      => 'append',
                                     filename  => File::Spec->catfile(
+LOG_DIR, LOG_FILE),
                                   )
);
$log->warning("Starting Processing:  ".time());


#
# Setup signal handlers so that we have time to cleanup before shuttin
+g down
#
my $keep_going = 1;
$SIG{HUP}  = sub { $log->warning("Caught SIGHUP:  exiting gracefully")
+; $keep_going = 0; };
$SIG{INT}  = sub { $log->warning("Caught SIGINT:  exiting gracefully")
+; $keep_going = 0; };
$SIG{QUIT} = sub { $log->warning("Caught SIGQUIT:  exiting gracefully"
+); $keep_going = 0; };
#$SIG{TERM} = sub { $log->warning("Caught SIGTERM:  exiting gracefully
+"); $keep_going = 0; };


#
# enter main loop
#
while ($keep_going) {

        # do something useful here


}

#
# Mark a clean exit in the log
#
$log->warning("Stopping Processing:  ".time());


#
# startDaemon
#
# Fork and detach from the parent process
#
sub startDaemon {

  #
  # Fork and detach from the parent process
  #
#  eval { close DATA; }; # having __END__ will trigger __DATA__ to ope
+n and should be closed
  eval { Proc::Daemon::Init; };
  if ($@) {
    dienice("Unable to start daemon:  $@");
  }

  #
  # Get a PID file
  #
  dienice("Already running!") if hold_pid_file($PIDFILE);
}

#
# dienice
#
# write die messages to the log before die'ing
#
sub dienice ($) {
  my ($package, $filename, $line) = caller;
  $log->critical("$_[0] at line $line in $filename");
  die $_[0];
}
[download]

Comment on Re: Writing a Perl Daemon Download Code

Replies are listed 'Best First'.
Re^2: Writing a Perl Daemon by onkar (Novice) on Dec 15, 2009 at 06:37 UTC
`# # startDaemon # # Fork and detach from the parent process # sub startDaemon { # # Fork and detach from the parent process # eval { Proc::Daemon::Init; }; if ($@) { dienice("Unable to start daemon: $@"); } # # Get a PID file # dienice("Already running!") if hold_pid_file($PIDFILE); } # # dienice # # write die messages to the log before die'ing # sub dienice ($) { my ($package, $filename, $line) = caller; $log->critical("$_[0] at line $line in $filename"); die $_[0]; }` [download] I am not getting any error ! but the daemon is also not running ? What might be wrong ! I tried to debug it , but it hangs !	[reply] [d/l]
Re^2: Writing a Perl Daemon by northshorefiend (Initiate) on Mar 15, 2013 at 11:35 UTC
One gotcha that got me is if you are using sockets to talk to the daemon, then remember to catch SIGPIPE, or ignore it: `$SIG{PIPE} = 'IGNORE';` [download]	[reply] [d/l]
Re^2: Writing a Perl Daemon by Anonymous Monk on Apr 17, 2013 at 15:59 UTC
You forgot to include your hold_pid_file function - prob why it doesn't work.	[reply]
Re^2: Writing a Perl Daemon by onkar (Novice) on Dec 15, 2009 at 05:52 UTC
DB<1> stop in Proc::Daemon::Init Debugged program terminated. Use q to quit or R to restart, use O inhibit_exit to avoid stopping after program termination, h q, h R or h O to get additional info. DB<2> Debugged program terminated. Use q to quit or R to restart, use O inhibit_exit to avoid stopping after program termination, h q, h R or h O to get additional info. ######### Forked, but do not know how to create a new TTY. ######### Since two debuggers fight for the same TTY, input is severely entangled. I know how to switch the output to a different window in xterms and OS/2 consoles only. For a manual switch, put the name of the created TTY in $DB::fork_TTY, or define a function DB::get_fork_TTY() returning this. On UNIX-like systems one can get the name of a TTY for the given window by typing tty, and disconnect the shell from TTY by sleep 1000000. {pid=5701} DB<2> s	[reply]


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