NAME

Daemon::Control - Create init scripts in Perl

DESCRIPTION

Daemon::Control provides a library for creating init scripts in perl. Your perl script just needs to set the accessors for what and how you want something to run and the library takes care of the rest.

You can launch programs through the shell (/usr/sbin/my_program) or launch Perl code itself into a daemon mode. Single and double fork methods are supported, and in double-fork mode all the things you would expect such as reopening STDOUT/STDERR, switching UID/GID etc are supported.

SYNOPSIS

Write a program that describes the daemon:

#!/usr/bin/perl
use warnings;
use strict;
use Daemon::Control;

exit Daemon::Control->new(
    name        => "My Daemon",
    lsb_start   => '$syslog $remote_fs',
    lsb_stop    => '$syslog',
    lsb_sdesc   => 'My Daemon Short',
    lsb_desc    => 'My Daemon controls the My Daemon daemon.',
    path        => '/home/symkat/etc/init.d/program',

    program     => '/home/symkat/bin/program',
    program_args => [ '-a', 'orange', '--verbose' ],

    pid_file    => '/tmp/mydaemon.pid',
    stderr_file => '/tmp/mydaemon.out',
    stdout_file => '/tmp/mydaemon.out',

    fork        => 2,

)->run;

By default run will use @ARGV for the action, and exit with an LSB compatible exit code. For finer control, you can use run_command, which will return the exit code, and accepts the action as an argument. This enables more programatic control, as well as running multiple instances of Daemon::Control from one script.

my $daemon = Daemon::Control->new(
    ...
);
my $exit = $daemon->run_command(“start”);

You can then call the program:

/home/symkat/etc/init.d/program start

You can also make an LSB compatible init script:

/home/symkat/etc/init.d/program get_init_file > /etc/init.d/program

CONSTRUCTOR

The constructor takes the following arguments as a list or a hash ref.

name

The name of the program the daemon is controlling. This will be used in status messages "name [Started]" and the name for the LSB init script that is generated.

program

This can be a coderef or the path to a shell program that is to be run.

$daemon->program( sub { ... } );

$daemon->program( "/usr/sbin/http" );

program_args

This is an array ref of the arguments for the program. In the context of a coderef being executed this will be given to the coderef as @_, the Daemon::Control instance that called the coderef will be passed as the first arguments. Your arguments start at $_[1].

In the context of a shell program, it will be given as arguments to be executed.

$daemon->program_args( [ 'foo', 'bar' ] );

$daemon->program_args( [ '--switch', 'argument' ] );

user

When set, the username supplied to this accessor will be used to set the UID attribute. When this is used, uid will be changed from its initial settings if you set it (which you shouldn't, since you're using usernames instead of UIDs). See "uid" for setting numerical user ids.

$daemon->user('www-data');

group

When set, the groupname supplied to this accessor will be used to set the GID attribute. When this is used, gid will be changed from its initial settings if you set it (which you shouldn't, since you're using groupnames instead of GIDs). See "gid" for setting numerical group ids.

$daemon->group('www-data');

uid

If provided, the UID that the program will drop to when forked. This is ONLY supported in double-fork mode and will only work if you are running as root. Accepts numeric UID. For usernames please see "user".

$daemon->uid( 1001 );

gid

If provided, the GID that the program will drop to when forked. This is ONLY supported in double-fork mode and will only work if you are running as root. Accepts numeric GID, for groupnames please see "group".

$daemon->gid( 1001 );

umask

If provided, the umask of the daemon will be set to the umask provided, note that the umask must be in oct. By default the umask will not be changed.

$daemon->umask( 022 );

Or:

$daemon->umask( oct("022") );

path

The path of the script you are using Daemon::Control in. This will be used in the LSB file generation to point it to the location of the script. If this is not provided, the absolute path of $0 will be used.

init_config

The name of the init config file to load. When provided your init script will source this file to include the environment variables. This is useful for setting a PERL5LIB and such things.

$daemon->init_config( "/etc/default/my_program" );

If you are using perlbrew, you probably want to set your init_config to $ENV{PERLBREW_ROOT} . '/etc/bashrc'.

init_code

When given, whatever text is in this field will be dumped directly into the generated init file.

$daemon->init_code( "Arbitrary code goes here." )

help

Any text in this accessor will be printed when the script is called with the argument --help or <help>.

$daemon->help( "Read The Friendly Source." );

redirect_before_fork

By default this is set to true. STDOUT will be redirected to stdout_file, and STDERR will be redirected to stderr_file. Setting this to 0 will disable redirecting before a double fork. This is useful when you are using a code reference and would like to leave the filehandles alone until you're in control.

Call ->redirect_filehandles on the Daemon::Control instance your coderef is passed to redirect the filehandles.

stdout_file

If provided stdout will be redirected to the given file. This is only supported in double fork mode.

$daemon->stdout_file( "/tmp/mydaemon.stdout" );

Alternatively, you can specify an arrayref of arguments to open():

$daemon->stdout_file( [ '>',  '/tmp/overwrite-every-run'  ] );
$daemon->stdout_file( [ '|-', 'my_pipe_program', '-a foo' ] );

stderr_file

If provided stderr will be redirected to the given file. This is only supported in double fork mode.

$daemon->stderr_file( "/tmp/mydaemon.stderr" );

Alternatively, you can specify an arrayref of arguments to open():

$daemon->stderr_file( [ '>',  '/tmp/overwrite-every-run'  ] );
$daemon->stderr_file( [ '|-', 'my_pipe_program', '-a foo' ] );

pid_file

The location of the PID file to use. Warning: if using single-fork mode, it is recommended to set this to the file which the daemon launching in single-fork mode will put its PID. Failure to follow this will most likely result in status, stop, and restart not working.

$daemon->pid_file( "/var/run/mydaemon/mydaemon.pid" );

resource_dir

This directory will be created, and chowned to the user/group provided in user, and group.

$daemon->resource_dir( "/var/run/mydaemon" );

prereq_no_process -- EXPERIMENTAL

This option is EXPERIMENTAL and defaults to OFF.

If this is set, then the ps list will be checked at startup for any processes that look like the daemon to be started. By default the pattern used is /\b<program name>\b/, but you can pass an override regexp in this field instead (to use the default pattern, just pass prereq_no_process => 1). If matching processes are found, those pids are output, and the daemon will not start.

This may produce some false positives on your system, depending on what else is running on your system, but it may still be of some use, e.g. if you seem to have daemons left running where the associated pid file is getting deleted somehow.

fork

The mode to use for fork. By default a double-fork will be used.

In double-fork, uid, gid, std*_file, and a number of other things are supported. A traditional double-fork is used and setsid is called.

In single-fork none of the above are called, and it is the responsibility of whatever you're forking to reopen files, associate with the init process and do all that fun stuff. This mode is recommended when the program you want to control has its own daemonizing code. It is important to note that the PID file should be set to whatever PID file is used by the daemon.

In no-fork mode, fork(0), the program is run in the foreground. By default quiet is still turned off, so status updates will be shown on the screen such as that the daemon started. A shortcut to turn status off and go into foreground mode is foreground being set to 1, or DC_FOREGROUND being set as an environment variable. Additionally, calling foreground instead of start will override the forking mode at run-time.

$daemon->fork( 0 );

$daemon->fork( 1 );

$daemon->fork( 2 ); # Default

scan_name

This provides an extra check to see if the program is running. Normally we only check that the PID listed in the PID file is running. When given a regular expression, we will also match the name of the program as shown in ps.

$daemon->scan_name( qr|mydaemon| );

kill_timeout

This provides an amount of time in seconds between kill signals being sent to the daemon. This value should be increased if your daemon has a longer shutdown period. By default 1 second is used.

$daemon->kill_timeout( 7 );

lsb_start

The value of this string is used for the 'Required-Start' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.

$daemon->lsb_start( '$remote_fs $syslog' );

lsb_stop

The value of this string is used for the 'Required-Stop' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.

$daemon->lsb_stop( '$remote_fs $syslog' );

lsb_sdesc

The value of this string is used for the 'Short-Description' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.

$daemon->lsb_sdesc( 'My program...' );

lsb_desc

The value of this string is used for the 'Description' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.

$daemon->lsb_desc( 'My program controls a thing that does a thing.' );

quiet

If this boolean flag is set to a true value all output from the init script (NOT your daemon) to STDOUT will be suppressed.

$daemon->quiet( 1 );

reload_signal

The signal to send to the daemon when reloading it. Default signal is HUP.

stop_signals

An array ref of signals that should be tried (in order) when stopping the daemon. Default signals are TERM, TERM, INT and KILL (yes, TERM is tried twice).

PLUGINS

Daemon Control supports a simple plugin system using Role::Tiny.

with_plugins

With plugins adds the plugins to Daemon::Control.

Daemon::Control->with_plugins( qw( MyFirstPlugin +MySecondPlugin) )->new(
...
);

Note:

MyFirstPlugin will load Daemon::Control::Plugin::MyFirstPlugin

+MySecondPlugin will load MySecondPlugin

Writing A Plugin

Your plugin should use the name Daemon::Control::Plugin::YourModuleName and YourModuleName should reasonably match the effect your plugin has on Daemon::Control.

You can replace Daemon::Control methods by writing your own and using Role::Tiny within your class to allow it to be composed into Daemon::Control.

The default Daemon::Control ships with no dependancies and supports Perl 5.8.1+, to use the plugin system your module MUST declare dependency on Role::Tiny and if you wish to use the around, before and after your module MUST declare dependance on Class::Method::Modifiers in your package.

METHODS

run_command

This function will process an action on the Daemon::Control instance. Valid arguments are those which a do_ method exists for, such as start, stop, restart. Returns the LSB exit code for the action processed.

run

This will make your program act as an init file, accepting input from the command line. Run will exit with 0 for success and uses LSB exit codes. As such no code should be used after ->run is called. Any code in your file should be before this. This is a shortcut for

exit Daemon::Control->new(...)->run_command( @ARGV );

do_start

Is called when start is given as an argument. Starts the forking and exits. Called by:

/usr/bin/my_program_launcher.pl start

do_foreground

Is called when foreground is given as an argument. Starts the program or code reference and stays in the foreground -- no forking is done, regardless of the compile-time arguments. Additionally, turns quiet on to avoid showing Daemon::Control output.

/usr/bin/my_program_launcher.pl foreground

do_stop

Is called when stop is given as an argument. Stops the running program if it can. Called by:

/usr/bin/my_program_launcher.pl stop

do_restart

Is called when restart is given as an argument. Calls do_stop and do_start. Called by:

/usr/bin/my_program_launcher.pl restart

do_reload

Is called when reload is given as an argument. Sends the signal reload_signal to the daemon.

/usr/bin/my_program_launcher.pl reload

do_status

Is called when status is given as an argument. Displays the status of the program, basic on the PID file. Called by:

/usr/bin/my_program_launcher.pl status

do_get_init_file

Is called when get_init_file is given as an argument. Dumps an LSB compatible init file, for use in /etc/init.d/. Called by:

/usr/bin/my_program_launcher.pl get_init_file

pretty_print

This is used to display status to the user. It accepts a message and a color. It will default to green text, if no color is explicitly given. Only supports red and green.

$daemon->pretty_print( "My Status", "red" );

write_pid

This will write the PID to the file in pid_file.

read_pid

This will read the PID from the file in pid_file and set it in pid.

pid

An accessor for the PID. Set by read_pid, or when the program is started.

dump_init_script

A function to dump the LSB compatible init script. Used by do_get_init_file.

AUTHOR

Kaitlyn Parkhurst (SymKat) <symkat@symkat.com> ( Blog: http://symkat.com/ )

CONTRIBUTORS

Matt S. Trout (mst) <mst@shadowcat.co.uk>
Mike Doherty (doherty) <doherty@cpan.org>
Karen Etheridge (ether) <ether@cpan.org>
Ævar Arnfjörð Bjarmason (avar) <avar@cpan.org>
Kieren Diment <zarquon@cpan.org<gt>
Mark Curtis <mark.curtis@affinitylive.com<gt>
Zoffix Znet <zoffix@cpan.org<gt>

COPYRIGHT

LICENSE

This library is free software and may be distributed under the same terms as perl itself.

AVAILABILITY

The most current version of Daemon::Control can be found at https://github.com/symkat/Daemon-Control

To install Daemon::Control, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Daemon::Control

CPAN shell

perl -MCPAN -e shell
install Daemon::Control

For more information on module installation, please visit the detailed CPAN module installation guide.

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