Bodgit & Scarper

I really like the idea of using Puppet and similar tools for automating as much of server configuration as possible. As I slowly “puppet-ify” things I find the need to sometimes add custom facts to facter, the part of Puppet that provides information about the host system.

This would be easy were it not for the small problem that custom facts are written in Ruby, a language I’m not fluent in, although this gives me a reason to learn the basics. I’m familiar with various other languages so it shouldn’t be that hard, here’s what I’ve managed to cobble together so far…

The first fact returns a list of the Linux software RAID block devices on the host. This is just parsing the /proc/mdstat file that should exist on any Linux distribution:

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Facter.add('software_raid') do
  confine :kernel => :linux
  setcode do
    devices = []
    if FileTest.exists?('/proc/mdstat')
      File.open('/proc/mdstat', 'r') do |f|
        while line = f.gets
          if line =~ /^(md\d+)/
            devices.push($1)
          end
        end
      end
    end
    devices.sort.join(',')
  end
end

This next recipe creates one fact per bonded network interface on Linux, containing the list of enslaved interfaces. This is specific to CentOS, Fedora, Red Hat or any other similar distributions that use the /etc/sysconfig configuration files:

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require 'find'
 
Facter.value(:interfaces).split(',').each do |interface|
  if interface =~ /^bond\d+$/
    Facter.add("#{interface}_slaves") do
      confine :kernel => :linux, :operatingsystem => %w{CentOS Fedora RedHat}
      setcode do
        slaves = []
        Find.find('/etc/sysconfig/network-scripts') do |path|
          if FileTest.directory?(path)
            next
          else
            if path =~ /ifcfg-(.+)$/
              device = $1
              File.open(path, 'r') do |f|
                while line = f.gets
                  if line =~ /^MASTER\s*=\s*#{interface}$/
                    slaves.push(device)
                  end
                end
              end
            end
          end
        end
        slaves.sort.join(',')
      end
    end
  end
end

I use these two facts within my Puppet manifests as the basis for configuring additional Nagios tests to make sure these two pieces of functionality are working correctly.

Tags: Custom Facts, Facter, Ruby

This entry was posted on Wednesday, July 28th, 2010 at 9:00 pm and is filed under Puppet. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.