cycletimes.rb

#!/usr/bin/env ruby -w

require 'time'
require 'json'

#
# Helper methods
#
module Enumerable
  def mean(method=:self)
    map(&method).reduce(:+) / size.to_f
  end
end

class CycleTimes

  HEROKU_APP = ARGV.shift or raise "Usage: #{$0} HEROKU_APP"
  RELEASE_COUNT = Integer(ENV['RELEASE_COUNT'] || 100)
  FORTNIGHT_AGO = (Date.today - 14).to_time

  def self.print
    new.print
  end

  def print
    puts fortnight_cycles
    puts
    puts "## #{HEROKU_APP}: Average Commit Cycle Time"
    puts "Fortnight: #{Cycle.stats(fortnight_cycles)}"
    puts "Overall: #{Cycle.stats(cycles)} since #{deploys.last.time}"
  end

private

  def fortnight_cycles
    @fortnight_cycles ||= cycles.select { |c| c.commit.time > FORTNIGHT_AGO }
  end

  def cycles
    @cycles ||= Commit.fetch_all(commit_range).map do |commit|
      Cycle.new(commit, current_deploy(commit))
    end
  end

  def commit_range
    @commit_range ||= "#{deploys.first.sha}...#{deploys.last.sha}"
  end

  def current_deploy(commit)
    @next_deploys ||= deploys.uniq(&:sha)
    @current_deploy = @next_deploys.shift if commit.sha == @next_deploys.first.sha
    @current_deploy
  end

  def deploys
    @deploys ||= Deploy.fetch_all(HEROKU_APP, RELEASE_COUNT)
  end

  Cycle = Struct.new(:commit, :deploy) do
    def self.duration(seconds)
      hours = seconds.to_i / 3600
      mins = (seconds.to_i - hours * 3600) / 60
      "#{hours}h #{mins}m"
    end

    def self.stats(cycles)
      deploys = cycles.uniq(&:deploy)
      "#{duration cycles.mean(:cycle_time)} (#{cycles.size} commits, #{deploys.size} deploys)"
    end

    def cycle_time
      @cycle_time ||= deploy.time - commit.time
    end

    def duration
      self.class.duration(cycle_time)
    end

    def to_s
      "#{commit.sha} #{commit.time} -> #{deploy.time} (#{duration}) #{commit.subject}"
    end
  end

  Deploy = Struct.new(:sha, :time) do

    def self.fetch_all(app, release_count)
      releases(app, release_count)
        .select { |release| release['description'].start_with?('Deploy') }
        .map(&method(:build))
    end

    def self.build(release)
      new(
        release['description'].match(/Deploy (\w+)/)[1],
        Time.parse(release['created_at'])
      )
    end

    def self.releases(app, count)
      JSON.parse `heroku releases --json --num #{count} --app #{app}`
    end

  end

  Commit = Struct.new(:sha, :time, :subject) do
    def self.fetch_all(commit_range)
      git_log_lines(commit_range).map do |line|
        sha, time, subject = line.split(' ', 3)

        new(sha, Time.parse(time), subject.strip)
      end
    end

    def self.git_log_lines(range)
      `git log --pretty="%h %aI %s" #{range}`.each_line
    end
  end

end

CycleTimes.print