oracular (3) Daemon::Control.3pm.gz
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 programmatic 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") );
directory
If provided, chdir to this directory before execution.
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 dependencies 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 dependence 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> SPONSORS Parts of this code were paid for by (mt) Media Temple <http://www.mediatemple.net>
COPYRIGHT
Copyright (c) 2012 the Daemon::Control "AUTHOR", "CONTRIBUTORS", and "SPONSORS" as listed above.
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>