mongo-metrics.rb

#! /usr/bin/env ruby


##
# three strategies of modeling metrics:
#
#   SimpleMetric: one metric per record
#
#   HashMetric: an array of metrics per record
#
#   EmbeddedMetric: an array of metric models per record
#
# the strategies of having sets per record would require some logic when one
# had to go back in time.
#
# the HashMetric is fastest and produces 1000s of times fewer records in the
# db.  interesting...


##
#
  require 'benchmark'

  require 'rubygems'
  require 'mongoid'

##
#
  Mongoid.configure do |config|
    config.master = Mongo::Connection.new.db("test")
  end

##
#
  N = Integer(ARGV.shift || 2 ** 13)

##
#
  class SimpleMetric
    include Mongoid::Document

    field(:kind)
    field(:value)

    def self.emit!(attributes = {})j
      create!(attributes)
    end

    def self.most_recent
      all.limit(N)
    end
  end

  class HashMetric
    include Mongoid::Document

    field(:metrics, :default => [])

    Instance = create!

    def self.emit!(attributes = {})
      Instance.push_all(:metrics, [attributes])
    end

    def self.most_recent
      last.metrics
    end
  end

  class EmbeddedMetric
    include Mongoid::Document

    class Metric
      include Mongoid::Document
      field(:kind)
      field(:value)
      embedded_in(:embedded_metric, :class_name => 'EmbeddedMetric')
    end
    embeds_many(:metrics, :class_name => 'EmbeddedMetric::Metric')

    Instance = create!

    def self.emit!(attributes = {})
      Instance.metrics.create!(attributes)
    end

    def self.most_recent
      last.metrics
    end
  end

##
#

  Benchmark.bm(3) do |bm|

    [ SimpleMetric, HashMetric, EmbeddedMetric ].each do |strategy|

      bm.report strategy.name do
        N.times do
          strategy.emit!(:kind => 'foo', :value => rand(10))
        end

        strategy.most_recent.each{}
      end

    end

  end


__END__

ruby a.rb

        user     system      total        real
        SimpleMetric  6.770000   0.290000   7.060000 (  7.067250)
        HashMetric  4.770000   0.130000   4.900000 (  4.931874)
        EmbeddedMetric 13.390000   0.200000  13.590000 ( 13.589994)