metrics.rb

#!/usr/bin/env ruby

require "webrick"

require 'sys/proctable'
include Sys

# Respond with 200 OK.
def respond_ok(response)
  response.status = 200
  response.body = "OK"
end

# Respond with 404 Not Found.
def respond_404(response)
  response.status = 404
  response.body = "Not Found"
end

def count_procs(state, ps)
  ps.map(&:state).select {|x| x == state}.size
end

def respond_metrics(response)
  ps = ProcTable.ps
states = {'R' => 'running',
'S' => 'sleeping',
'D' => 'disk sleep',
'T' => 'stopped',
't' => 'tracing stop',
'X' => 'dead',
'Z' => 'zombie'}
# node_processes{status="stopped"} 1
r_body = ''
states.each do |k,v|
  r_body += "node_processes{status=\"#{v}\"} #{count_procs(k,ps)}\n"
end

  response.status = 200
  response.body = r_body
end

# A simple HTTP router.
class HTTPRouter < WEBrick::HTTPServlet::AbstractServlet
  def do_GET(request, response)
    if request.path == "/health"
      respond_ok(response)
    elsif request.path == "/metrics"
      respond_metrics(response) 
    else
      respond_404(response)
    end
  end
end

server = WEBrick::HTTPServer.new(:Port => 9150, :DoNotReverseLookup => true)
server.mount("/", HTTPRouter)
server.start