Help-Site Computer Manuals
Software
Hardware
Programming
Networking
  Algorithms & Data Structures   Programming Languages   Revision Control
  Protocols
  Cameras   Computers   Displays   Keyboards & Mice   Motherboards   Networking   Printers & Scanners   Storage
  Windows   Linux & Unix   Mac

Daemon::Generic
framework to provide start/stop/reload for a daemon

Daemon::Generic - framework to provide start/stop/reload for a daemon


NAME


 Daemon::Generic - framework to provide start/stop/reload for a daemon


SYNOPSIS


 use Daemon::Generic;

 sub gd_run { ... stuff }

 sub gd_preconfig { ... stuff }

 newdaemon();


DESCRIPTION

Daemon::Generic provides a framework for starting, stopping, reconfiguring daemon-like programs. The framework provides for standard commands that work for as init.d files and as apachectl-like commands.

Programs that use Daemon::Generic subclass Daemon::Generic to override its behavior. Almost everything that Genric::Daemon does can be overridden as needed.


EXAMPLE USAGE OUTPUT

Unless overriden, the usage output for your program will look something like this:


 Usage: $progname [ -c file ] [ -f ] { start | stop | reload | restart | help | version | check }

  -c            Specify configuration file (defaults to $configfile)

  -f            Run in the foreground (don't detach)

  start         Starts a new $progname if there isn't one running already

  stop          Stops a running $progname

  reload        Causes a running $progname to reload it's config file.  Starts

                a new one if none is running.

  restart       Stops a running $progname if one is running.  Starts a new one.

  check         Check the configuration file and report the daemon state

  help          Display this usage info

  version       Display the version of $progname


CONSTRUCTION

To hand control over to Daemon::Generic, call newdaemon(). Control will be handed back through method calls to functions you define.

Your @ISA will be modified to include Daemon::Generic if if it isn't already there.

These are the arguments to newdaemon(). Defaults are in (parenthesis).

progname
($0) The name of this program. This will be used for logging and for naming the PID file.

configfile
(/etc/$progname.conf) The location of the configuration file for this daemon.

pidbase
(/var/run/$progname) We include the configuration file name as part of the pid file in case there are multiple instances of this deamon. The pidbase is is the part of the PID file that does not include the configuration file name.

pidfile
($pidbase.$configfile.pid) The location of the process id file.

foreground
(0) Do not detach/daemon and run in the foreground instead.

debug
(0) Turn on debugging.

no_srand
(0) Normall srand() is called. If no_srand is set then srand() won't be called.

options
() Additional arguments for the Getopt::Long::GetOptions manpage which is used to parse @ARGV. Alternatively: define &gd_more_opt().

minimum_args
(1) Minimum number of @ARGV arguments after flags have been processed.

maximum_args
(1) Maximum number of @ARGV arguments after flags have been processed.

version
($pkg::VERSION) The version number of the daemon.

logpriority
Used for logger -p.


MUST-OVERRIDE CALLBACK METHODS

The package that subclasses Daemon::Generic must provide the following callback methods.

gd_preconfig()
gd_preconfig() is called to parse the configuration file ($self->{configfile}). Preconfig is called on all invocations of the daemon (daemon reload, daemon check, daemon stop, etc). It shouldn't start anything but it can and should verify that the config file is fine.

The return value should be a hash. With one exception, the return value is only used by gd_postconfig(). The exception is that gd_preconfig() may return a revised PID file location (key pidfile).

gd_run()
This is where you put your main program.


MAY-OVERRIDE CALLBACK METHODS

The package that subclasses Daemon::Generic does not have to override these methods but it may want to.

gd_postconfig(%config)
Postconfig() is called only when the daeamon is actually starting up. (Or on reconfigs). It is passed the return value from gd_preconfig.

gd_setup_signals()
Set things up so that SIGHUP calls gd_reconfig_event() and SIGINT calls gd_quit_event(). It will call these at any time so if you want to delay signal delivery or something you should override this method.

gd_getopt()
This is invoked to parse the command line. Useful things to modify are:
$self->{configfile}
The location of the configuration file to be parsed by gd_preconfig().

$self->{foreground}
Run in the foreground (don't daemonize).

$self->{debug}
Use it yourself.

The supplied gd_getopt() method uses the Getopt::Long manpage.

gd_parse_argv()
Parse any additional command line arguments beyond what gd_getopt() handled.

$ARGV[0] needs to be left alone if it is one of the following standard items:

start
Start up a new daemon.

stop
Stop the running daemon.

restart
Stop the running daemon, start a new one.

reload
Send a signal to the running daemon, asking it to reconfigure itself.

check
Just check the configuration file.

help
Print the help screen (probably usage()).

version
Display the daemon's version.

There is no default gd_parse_argv().

gd_check($pidfile, $pid)
Normal behavior: return. Define additional checks to run when the check command is given. A $pid will only be supplied if there is a daemon running.

gd_version()
Normal behavior: display a version message and exit.

gd_help()
Normal behavior: call gd_usage().

gd_commands_more()
Used by gd_usage(): provide information on additional commands beyond start, stop, reload, etc. Return is an array of key value pairs.

 sub gd_commands_more 

 {

        return (

                savestate => 'Tell xyz server to save its state',

                reset     => 'Tell xyz servr to reset',

        );

 }

gd_flags_more
Like gd_commands_more() but defines additional command line flags. There should also be a gd_more_opt() or an options argument to new().

gd_positional_more
Like gd_commands_more() but defines positional arguments.

gd_usage()
Display a usage message. The return value from gd_usage() is the exit code for the program.

gd_more_opt()
() Additional arguments for the Getopt::Long::GetOptions manpage which is used to parse @ARGV. Alternatively: pass options to new().

gd_pidfile()
Figure out the PID file should be.

gd_error()
Print out an error (call die?)

gd_other_cmd()
Called $ARGV[0] isn't one of the commands that Daemon::Generic knows by default. Default behavior: call gd_usage() and exit(1).

gd_daemonize()
Normal behavior: fork(), fork(), detach from tty.

gd_redirect_output()
Normal behavior: redirect STDOUT and STDERR to logger -t $progname[$$]. Used by gd_daemonize().

gd_logname()
Normal behavior: $progname[$$]. Used by gd_redirect_output().

gd_reconfig_event()
Normal behavior: call gd_postconfig(gd_preconfig)). Only referenced by gd_setup_signals().

gd_quit_event()
Normal behavior: exit. Only referenced by gd_setup_signals().

gd_kill($pid)
Used by the stop and restart commands to get rid of the old daemon. Normal behavior: send a SIGINT. Check to see if process $pid has died. If it has not, keep checking and if it's still alive. After $Daemon::Generic::force_quit_delay seconds, send a SIGTERM. Keep checking. After another $Daemon::Generic::force_quit_delay seconds, send a SIGKILL (-9). Keep checking. After $Daemon::Generic::force_quit_delay * 4 seconds or 60 seconds (whichever is smaller), give up and exit(1).

gd_install
Installs the daemon so that it runs automatically at next reboot. Currently done with a symlink to $0 and /usr/sbin/update-rc.d. Please send patches for other methods!

gd_can_install
Returns a function to do an gd_install if installation is possible. Returns 0 otherwise.

gd_install_pre($method)
Normal behavior: return. Called just before doing an installation. The method indicates the installation method (currently always update-rc.d.)

gd_install_post($method)
Normal behavior: return. Called just after doing an installation.

gd_uninstall
Will remove the daemon from the automatic startup regime.

gd_can_uninstall
Returns a function to do the work for gd_uninstall if it's possible. 0 otherwise.

gd_uninstall_pre($method)
Normal behavior: return. Called just before doing an un-installation. The method indicates the installation method (currently always update-rc.d.)

gd_install_post($method)
Normal behavior: return. Called just after doing an un-installation.


MEMBER DATA

Since you need to subclass Daemon::Generic, you need to know what the internal data structures for Daemon::Generic are. With two exceptions, all of the member data items begin with the prefix gd_.

configfile
The location of the configuration file. (Not used by Daemon::Generic).

debug
Display debugging? (Not used by Daemon::Generic)

gd_args
The original %args passed to new.

gd_progname
The process name. (defaults to $0)

gd_pidfile
The location of the process ID file.

gd_logpriority
Used for logger -p.

gd_foreground
Are we running in the foreground?


EXAMPLE PROGRAM


 my $sleeptime = 1;

 newdaemon(

        progname        => 'ticktockd',

        pidfile         => '/var/run/ticktockd.pid',

        configfile      => '/etc/ticktockd.conf',

 );

 sub gd_preconfig

 {

        my ($self) = @_;

        open(CONFIG, "<$self->{gd_configfile}") or die;

        while(<CONFIG>) {

                $sleeptime = $1 if /^sleeptime\s+(\d+)/;

        }

        close(CONFIG);

        return ();

 }

 sub gd_run

 {

        while(1) {

                sleep($sleeptime);

                print scalar(localtime(time))."\n";

        }

 }


SEE ALSO

With a while(1) and delayed signal delivery: the Daemon::Generic::While1 manpage.

With Event: the Daemon::Generic::Event manpage.

Modules that use Daemon::Generic: the SyslogScan::Daemon manpage the IO::Event manpage (rinetd.pl)

Other modules that do similar things: the Net::Daemon manpage, the Net::Server manpage, the Net::Server::Daemonize manpage, the NetServer::Generic manpage, the Proc::Application::Daemon manpage, the Proc::Daemon manpage, the Proc::Forking manpage.


THANK THE AUTHOR

If you need high-speed internet services (T1, T3, OC3 etc), please send me your request-for-quote. I have access to very good pricing: you'll save money and get a great service.


LICENSE

Copyright(C) 2006 David Muir Sharnoff <muir@idiom.com>. This module may be used and distributed on the same terms as Perl itself.

Programminig
Wy
Wy
yW
Wy
Programming
Wy
Wy
Wy
Wy