Pulse 1.0

Author: Kevin Boyd (aka Beryllium) <[email protected]> http://beryllium.ca/

Description:

This script is intended to allow system administrators to determine that all of their systems are up-to-date, 
functional, and generally happy.

It can also be used as a quick hit-point for Amazon Elastic Load Balancer health checks, since it returns HTTP-200.

I have some grandiose ideas for how it can be used, but I'll get to that later :) For now, I am just putting 
it out there in PHP and looking for input on what other tidbits of data might be useful for sysadmins. And hey, 
ports to other languages are welcome, too, as long as the output is cross-compatible :)

Requirements:
  A non-Windows operating system (for system calls, like loadavg - I'd like it to be cross-platform, though)
  PHP
  MCrypt
  ?? I dunno. Maybe some PHP5.3 stuff, but there shouldn't be too much of that.

Configuration:

Open the script and set the $keymaster and $gatekeeper values.

  $keymaster    This is the secret key used to encrypt the content. Pulse will need to know it, and your 
                analysis platform will need to know it, but it should never be passed in an HTTP POST or HTTP GET.
    
  $gatekeeper   This is the Gatekeeper; attaching this to the URL will cause the encrypted string to be 
                built and spat out.

Usage:
  $data = file_get_contents( 'http://slimer.example.com/pulse.php?gatekeeper=ZUUL' );

  $array = unserialize( mcrypt_decrypt( 
        MCRYPT_RIJNDAEL_256, 
        'my secret keymaster value which is of course STAY PUFT MARSHMALLOW MAN',
        $data,
        MCRYPT_MODE_ECB );

  print_r( $array );