Monitoring your unicorn workers with Sensu

unicorn.rb

# Monitor the unicorn processes on 10 second intervals
unicorn_monitor = Proc.new {
  require 'socket'
  require 'json'
  require 'raindrops'
  address = "0.0.0.0:8080"
  socket = Raindrops::InetDiagSocket.new
  udp = UDPSocket.new

  while(true) do
    begin
      data = Raindrops::Linux.tcp_listener_stats(address, socket)
      stat = data[address]

      output = [:active, :queued].map { |t|
        ["#{Socket.gethostname}.unicorn.#{t}", stat.send(t), Time.now.to_i].join("\t")
      }.join("\n") + "\n" # all graphite input must end in a newline

      check = {
        :handlers => ["metrics"],
        :name => 'unicorn-metrics',
        :status => 0,
        :output => output,
        :type => 'metric'
      }

      udp.send(check.to_json, 0, '0.0.0.0', 3030)
    rescue # make sure thread doesn't accidently die
    end

    sleep(10)
  end
}

Thread.new(&unicorn_monitor)