gistfile1.rb

class ReactorLatency < Graph
  name 'reactor_latency'
  vlabel 'microseconds'
  scale 'no'
  category 'application'

  next_tick 'next_tick latency'
  timer 'timer latency'

  def self.fetch
    start = Time.now
    EM.add_timer(0){
      diff = Time.now-start
      value :timer, "%f" % (diff*1_000_000)

      start = Time.now
      EM.next_tick{
        diff = Time.now-start
        value :next_tick, "%f" % (diff*1_000_000)

        super
      }
    }
  end
end

EM.run{
  # Run a munin node on port 4949. You must configure a munin master to poll this node for data.
  Graph::Server.start 'node.example.com', :port => 4949
}

gistfile2.rb

class String
  def space_case
    gsub(/([a-z]|[A-Z]+)([A-Z])/){ "#{$1} #{$2}" }
  end
  def snake_case
    gsub(/\B[A-Z][^A-Z]/, '_\&').downcase.gsub(' ', '_')
  end
end

class Graph
  List = [] unless defined? List

  def self.inherited klass
    List << klass
    klass.instance_variable_set('@title', klass.to_s.space_case)
    klass.instance_variable_set('@data', {})
  end

  def self.name n = nil
    if n
      @name = n
    else
      @name ||= to_s
    end
  end

  Attributes = %w[ title vlabel category info args order scale period ].map{|a| a.intern } unless defined? Attributes

  Attributes.each do |prop|
    class_eval %[
      def self.#{prop} str = nil
        if str
          @#{prop} = str
        else
          @#{prop}
        end
      end
    ]
  end

  def self.config
    config = Attributes.inject('') do |attrs, prop|
      if val = __send__(prop)
        attrs << "graph_#{prop} #{val}\n"
      end
      attrs
    end

    @data_keys ||= []
    @data ||= {}

    @data_keys.uniq.each do |key|
      @data[key].each do |type, setting|
        next if type == :value
        config << "#{key}.#{type} #{setting}\n"
      end
    end

    config
  end

  def self.default opts = nil
    if opts
      @default = opts
    else
      @default || {}
    end
  end
  
  def self.data name, desc, opts = {}
    (@data_keys ||= []) << name
    (@data[name] ||= {}).merge! default.merge(opts).merge(:label => desc)
  end

  class << self; alias :method_missing :data end

  def self.value name, val = nil
    if val
      @data[name][:value] = val
    else
      @data[name][:value]
    end
  end

  def self.fetch
    output = @data.inject('') do |attrs, (key, val)|
      attrs << "#{key}.value #{val[:value]}\n" if val[:value]
      attrs
    end

    yield output
  end
end

module Graph::Server
  def initialize node, opts
    @node, @settings = node, opts
  end

  def post_init
    set_comm_inactivity_timeout 250
    send_data "# munin node at #{@node}\n"
  end

  def receive_data data
    (@buf ||= BufferedTokenizer.new).extract(data).each do |line|
      case line.strip
      when /^list/
        send_data Graph::List.map{|g| g.name }.join(" ") + "\n"
      when /^config\s*(.*)/
        if graph = Graph::List.find{|g| g.name == $1 }
          send_data graph.config
        else
          send_data "# Unknown service\n"
        end
        send_data ".\n"
      when /^fetch\s*(.*)/
        if graph = Graph::List.find{|g| g.name == $1 }
          graph.fetch{ |data|
            send_data data
            send_data ".\n"
          }
        else
          send_data "# Unknown service\n"
          send_data ".\n"
        end
      when /^nodes/
        send_data "#{@node}\n"
        send_data ".\n"
      when /^version/
        send_data "munins node on #{@node} version: 1.2.5\n"
      when /^quit/
        close_connection
      else
        send_data "# Unknown command. Try list, nodes, config, fetch, version or quit\n"
      end
    end
  end

  class Error < Exception; end

  def self.start node, opts = {}
    if socket = opts[:socket]
      FileUtils.rm socket if File.exist? socket
      at_exit{ FileUtils.rm socket if File.exist? socket }
      server = EM.start_server socket, self, node, opts
      FileUtils.chmod 0777, socket
      server
    elsif opts[:port]
      EM.start_server opts[:host] || 'localhost', opts[:port], self, node, opts
    else
      raise Error, 'no socket or port provided'
    end
  end
end

reactor_latency-week.png