Run an arbitrary command on every puppet node registered to the puppet master

puppet-node-run.rb

#!/usr/bin/env ruby
require 'excon'
require 'json'
require 'net/dns'
include Net::DNS

# 
# Run an arbitrary command using parallel-ssh against all the nodes
# registered in the puppet master
# Needs pssh (parallel-ssh) installed.
#
# Usage: puppet-node-run <command>
#
# i.e. puppet-node-run puppet agent -t
# 

# Replace with the URL of your puppet master
MASTER_URL = "http://puppet:8080/nodes"
DNS_SERVER = "my-dns-server-address"

if ARGV.empty?
  $stderr.puts "Invalid command."
  $stderr.puts 
  $stderr.puts "Usage: puppet-node-run <command> <args>"
  exit 1
end

out = Excon.get MASTER_URL
nodes = JSON.parse out.body

# 
# Optionally resolve names using specific DNS server
#
# res = Resolver.new
# res.nameservers = DNS_SERVER
#

# Generate the list of nodes for parallel-ssh
puts "Generating hostlist..."
File.open '/tmp/hostlist', 'w' do |f|
  nodes.each do |i|
    address = i
    # try to resolve before writing the list
    # address = res.query(i).answer.first.address rescue next
    f.puts "#{address} root"
  end
end

#
# Run the command, ignoring bad host keys (useful while in development)
# The output for every node is saved in /tmp/root@XXXXXX
#
$stdout.sync = true
command = ARGV.join(' ')
puts "Running command '#{command}' with parallel-ssh..."
system 'parallel-ssh -o /tmp -t 120 -h /tmp/hostlist -x "-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null" ' + "'#{command}'"