#
# control-services.pl -- Monitor a listed set of services to be sure
#             they are running.  If not running, modify the DNS system
#             to remove them from the lookup for that service
#
#  '$RCSfile$'
#  Copyright: 2005 Regents of the University of California 
#
#   '$Author: jones $'
#     '$Date: 2005-10-13 22:43:22 +0000 (Thu, 13 Oct 2005) $'
# '$Revision: 2674 $' 
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software
#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

Welcome to the control-services.pl program.

This program is designed to run as a script under the Hobbit system monitoring
program (http://hobbitmon.sourceforge.net/).  When Hobbit is configured 
properly, this script will be called to make changes to the DNS services that
are registered in your DNS server.  The changes are accomplished using 
Dynamic DNS (DDNS).  The system is intended to help manage a set of services
that are running on several hosts in round-robin DNS fashion and to remove
inaccessible hosts when they are detected as failed, and restore them when 
they recover.

Configuration consists of:
  1) Install and configure Hobbit (see http://hobbitmon.sourceforge.net)
  2) Install and configure BIND for DDNS (see below)
  3) Install this script (see below)

3) Setting up BIND for DDNS
-----------------------------

You need to configure BIND to accept signed dynamic updates for your zone.  

    a) Create a key using dnssec-keygen.

        % dnssec-keygen  -b 256 -n HOST -a HMAC-MD5 example

        This will create 2 key files in different formats

    b) Add the key to your named.conf file in a block (copy it from either 
       of the two generated key files):

        key "examplekey" {
            algorithm       hmac-md5;
            secret "0QI/OEYtZA5aI6rpMTwrodfMpg1xxCaDHdR/tvI9Lgc=";
        };

    c) For each zone that you want to enable updates, add this key to
       your 'allow-update' and 'allow-transfer' blocks:
    
       zone "example.com" {
           type master;
           file "/var/named/example.com.zone"
           allow-update ( key examplekey; };
           allow-transfer { key examplekey; };
       }

    d) Reload named to reload your configuration (killall -HUP named).

3) Install the control-services.pl script
-----------------------------------------
Prerequisites:

    The following Perl Modules are required:
        Net::DNS
        LWP::UserAgent
        HTTP::Request
        HTTP::Response
        URI::URL
    These modules are available through CPAN, and are most easily gotten using
    the CPAN shell (as root, "perl -MCPAN -e shell").

Installation:
  1) copy the file to a commonly accessible location (typically /usr/local/bin)
  2) change ownership to the web-server user
  3) copy the configuration file to /etc and customize for your situation
     -- set the key name and value from your DDNS server
     -- set domain and other parameters properly
  4) change ownership of the config file to the web-server user
  5) restrict access to the config file to only the web server user
  6) Create the log file directory, writable by the hobbit user
  7) Place alert rules in the hobbit/server/etc/hobbit-alerts.cfg file that
     use the script.  See the hobbit-alerts.cfg man page for details. An
     example rule might be:

     HOST=ldap.example.com SERVICE=ldap RECOVERED
          SCRIPT /usr/local/bin/control-services.pl ldap FORMAT=SCRIPT REPEAT=1


IMPORTANT NOTE
----------------
Make sure that the configuration file is only readable by the webserver user
and writable by root. The config file contains the key to allow updates
to your DNS server, so be sure the config file is secure.

Enjoy!
