Monitoring radmind (updated)


(Updated 5/7/04) Once you have set up some sort of automation for radmind, so that it runs automatically every night, for example, it becomes important to be able to monitor the machines you manage to see if they are running radmind regularly and to be notified if there are any problems.

The run_radmind script we use emails us if there is a failure. But what if the failure is that the script never runs at all? Do you want to assume that because you haven't been notified of a problem, that everything is fine? So we have the script also perform an action on success. Since the vast majority of our machines are successful, and a large chunk of them run radmind every night, we don' t want to be buried in emails telling us everything is OK.

So on success, our run_radmind script calls a web CGI like so (in Perl):

#check in with the radmind check-in cgi
system "curl http://radmind/cgi-bin/radmindCheckin";

and here's the CGI:

#!/usr/bin/perl

# Radmind checkin CGI
#
# this simple CGI touches a file in $UPDATE_DIR
# with the hostname of the the machine reporting in (This assumes
# your machine's hostnames are in DNS and reverse lookup works)
# otherwise it touches a file named the same as the IP address of
# the machine reporting in.
#
# Copyright 2003 Walt Disney Feature Animation
# Permission granted to use this code freely.
#
# this CGI can be called from a script like so:
# curl "http://your.webserver.tld/cgi-bin/radmindCheckin"
#
# Original Script by Greg Neagle, WDFA.
#
# 02/11/2004 Modification of the original code to support running on Panther Server
# - Lance Ogletree , Rice University
#
# 05/06/2004 Modification to deal with Apache sometimes returning the remote IP in
# $ENV{SERVER_ADDR} and sometimes in $ENV{HTTP_PC_REMOTE_ADDR},
# depending on the server configuration.
# This should make the script more portable.
# Thanks to Josh Burker, Mercer Island School District for helping debug
# this issue.
# - Greg Neagle, WDFA
#
# 05/06/2004 Added ability to pass in a custom hostname; this might make this script
# usable in environments where useful hostnames are not in DNS.
# You could then have the machine grab a name from a file or by using
# `scutil --get LocalHostName` or `scutil --get ComputerName`
# You'd then call the CGI like so:
# curl "http://your.webserver.tld/cgi-bin/radmindCheckIn?mycustomhostname
# - Greg Neagle, WDFA
#

print "Content-type: text/plain\n";
print "\n";

print "Radmind check-in\n";
print "\n";

$UPDATE_DIR = "/var/radmind/client/updated/";
# be sure the directory pointed to by $UPDATE_DIR exists
# and that it's writable by the web server

$hostname = $ENV{QUERY_STRING};

if ($hostname eq "") {
   #no custom hostname passed in, so let's generate one
   $IP = $ENV{HTTP_PC_REMOTE_ADDR};

   if ($IP eq "") {
      # depending on Apache config/environment
      # we need to use $ENV{REMOTE_ADDR} instead
      $IP = $ENV{REMOTE_ADDR};
   }

   $hostoutput = `host $IP`;
   unless ($hostoutput =~ /not found/) {
      # parse out the hostname
      @hostoutput = split /\s+/, $hostoutput;
      $hostname = pop @hostoutput;
      $hostname =~ s/\.$//;
   } else {
      # use the IP as the hostname
      $hostname = $IP;
   }
}

print "$hostname successfully checked in.\n";
$cmd = "/usr/bin/touch $UPDATE_DIR$hostname";
`$cmd`;


The CGI is very simple. All it does is take the IP address of the incoming connection, look up the DNS hostname of that IP address, and then "touches" a file with the name of the host in a directory we've created to hold these (We used "/var/radmind/client/updated/").
The "touch" command creates an empty file if one does not exist, or updates the modification date on the file if it already exists.
If there is no hostname associated with the IP address, it touches a file named after the IP address ("192.168.1.1").
Finally, you can pass the CGI a hostname - this could be useful if the machine has a file it can use to come up with a unique name (like a radmind certificate), or you've set the "Computer Name" or Rendezvous name. In this case, you'd call the CGI like so (again in Perl):

system "curl http://radmind/cgi-bin/radmindCheckin?customhostname";

You can then tell the last time a machine successfully ran radmind by looking at the modification date of the file with its name. We have another CGI which presents this info in a nice web page. Details in anther entry on this site.

Since I originally posted this script last December, Lance Ogletree contributed a modification that lets it run properly under Panther, Josh Berker surfaced an issue (and helped me debug it) with some configurations of Apache, and I added the custom hostname feature.

Enjoy.

Posted: Fri - May 7, 2004 at 10:46 PM      

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