NAME
Cluster::Init - Clusterwide "init", spawn cluster applications
SYNOPSIS
use Cluster::Init;
my $init = new Cluster::Init;
# spawn all apps for resource group "foo", runlevel "run"
$init->tell("foo","run");
# spawn all apps for resource group "foo", runlevel "runmore"
# (this stops everything started by runlevel "run")
$init->tell("foo","runmore");
DESCRIPTION
This module provides basic "init" functionality, giving you a single
inittab-like file to manage initialization and daemon startup across a
cluster or collection of machines.
USAGE
This module's package includes a script 'clinit', which is intended to
be a bolt-in cluster init tool, calling Cluster::Init. The script is called
like 'init', with the addition of a new "resource group" argument.
This module is intended to be used like 'init' and 'telinit' -- the
first execution runs as a daemon, spawning and managing processes. Later
executions talk to the first, requesting it to switch to different
runlevels.
The module references a configuration file, /etc/clinittab by default,
which is identical in format to /etc/inittab, with a new "resource
group" column added. This file must be replicated across all hosts in
the cluster by some means.
A "resource group" is a collection of applications and physical
resources which together make up a coherent function. For example,
sendmail, /etc/sendmail.cf, and the /var/spool/mqueue directory might
make up a resource group. From /etc/clinittab you could spawn the
scripts which update sendmail.cf, mount mqueue, and then start sendmail
itself.
PUBLIC METHODS
new
The constructor accepts an optional hash containing the paths to the
configuration file and to the socket, like this:
my $init = new Cluster::Init (
'config' => '/etc/clinittab',
'socket' => '/var/run/clinit/init.s'
);
The first time this method is executed on a machine, it opens a UNIX
domain socket, /var/run/clinit/init.s by default. Subsequent executions
communicate with the first via this socket.
tell($resource_group,$runlevel)
This method talks to a running Cluster::Init daemon, telling it to switch the
given resource group to the given runlevel.
All processes listed in the configuration file (normally /etc/clinittab)
which belong to the new runlevel will be started if they aren't already
running.
All processes in the resource group which do not belong to the new
runlevel will be killed.
Other resource groups will not be affected.
PRIVATE METHODS
These methods and functions are considered private and are intended for
internal use by this module. They are not considered part of the public
interface and are described here for documentation purposes only.
_open_socket
BUGS
AUTHOR
Steve Traugott
CPAN ID: STEVEGT
[email protected]
http://www.stevegt.com
COPYRIGHT
Copyright (c) 2001 Steve Traugott. All rights reserved. This program is
free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
The full text of the license can be found in the LICENSE file included
with this module.
SEE ALSO
perl(1).
