initial commit

.gitignore

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+coverage/

README.md

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+# Heroku::Autoscale
+
+## Installation
+
+    # Gemfile
+    gem 'heroku-autoscale'
+
+## Usage (Rails 2.x)
+
+    # config/environment.rb
+    config.middleware.use Heroku::Autoscale,
+      :username  => ENV["HEROKU_USERNAME"],
+      :password  => ENV["HEROKU_PASSWORD"],
+      :app_name  => ENV["HEROKU_APP_NAME"],
+      :min_dynos => 2,
+      :max_dynos => 5,
+      :queue_wait_low  => 100,  # milliseconds
+      :queue_wait_high => 5000, # milliseconds
+      :min_frequency   => 10    # seconds
+
+## Usage (Rails 3 / Rack)
+
+    # config.ru
+    use Heroku::Autoscale,
+      :username  => ENV["HEROKU_USERNAME"],
+      :password  => ENV["HEROKU_PASSWORD"],
+      :app_name  => ENV["HEROKU_APP_NAME"],
+      :min_dynos => 2,
+      :max_dynos => 5,
+      :queue_wait_low  => 100,  # milliseconds
+      :queue_wait_high => 5000, # milliseconds
+      :min_frequency   => 10    # seconds

Rakefile

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+require "rake"
+require "rspec"
+require "rspec/core/rake_task"
+
+$:.unshift File.expand_path("../lib", __FILE__)
+require "heroku/autoscale"
+
+task :default => :spec
+task :release => :man
+
+desc "Run all specs"
+Rspec::Core::RakeTask.new(:spec) do |t|
+  t.pattern = 'spec/**/*_spec.rb'
+end
+
+desc "Generate RCov code coverage report"
+task :rcov => "rcov:build" do
+  %x{ open coverage/index.html }
+end
+
+Rspec::Core::RakeTask.new("rcov:build") do |t|
+  t.pattern = 'spec/**/*_spec.rb'
+  t.rcov = true
+  t.rcov_opts = [ "--exclude", Gem.default_dir , "--exclude", "spec" ]
+end
+
+######################################################
+
+begin
+  require 'jeweler'
+  Jeweler::Tasks.new do |s|
+    s.name    = "heroku-autoscale"
+    s.version = Heroku::Autoscale::VERSION
+
+    s.summary     = "Autoscale your Heroku dynos"
+    s.description = s.summary
+    s.author      = "David Dollar"
+    s.email       = "ddollar@gmail.com"
+    s.homepage    = "http://github.com/ddollar/heroku-autoscale"
+
+    s.platform = Gem::Platform::RUBY
+    s.has_rdoc = false
+
+    s.files = %w(Rakefile README.md) + Dir["{bin,export,lib,spec}/**/*"]
+    s.require_path = "lib"
+
+    s.add_development_dependency 'rack-test', '~> 0.5.4'
+    s.add_development_dependency 'rake',      '~> 0.8.7'
+    s.add_development_dependency 'rcov',      '~> 0.9.8'
+    s.add_development_dependency 'rr',        '~> 0.10.11'
+    s.add_development_dependency 'rspec',     '~> 2.0.0'
+
+    s.add_dependency 'eventmachine'
+    s.add_dependency 'heroku', '~> 1.9'
+    s.add_dependency 'rack',   '~> 1.0'
+  end
+  Jeweler::GemcutterTasks.new
+rescue LoadError
+  puts "Jeweler not available. Install it with: sudo gem install jeweler"
+end

heroku-autoscale.gemspec

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+# Generated by jeweler
+# DO NOT EDIT THIS FILE DIRECTLY
+# Instead, edit Jeweler::Tasks in Rakefile, and run the gemspec command
+# -*- encoding: utf-8 -*-
+
+Gem::Specification.new do |s|
+  s.name = %q{heroku-autoscale}
+  s.version = "0.1"
+
+  s.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version=
+  s.authors = ["David Dollar"]
+  s.date = %q{2010-07-09}
+  s.description = %q{Autoscale your Heroku dynos}
+  s.email = %q{ddollar@gmail.com}
+  s.files = [
+    "Rakefile",
+     "lib/heroku/autoscale.rb"
+  ]
+  s.has_rdoc = false
+  s.homepage = %q{http://github.com/ddollar/heroku-autoscale}
+  s.rdoc_options = ["--charset=UTF-8"]
+  s.require_paths = ["lib"]
+  s.rubygems_version = %q{1.3.7}
+  s.summary = %q{Autoscale your Heroku dynos}
+
+  if s.respond_to? :specification_version then
+    current_version = Gem::Specification::CURRENT_SPECIFICATION_VERSION
+    s.specification_version = 3
+
+    if Gem::Version.new(Gem::VERSION) >= Gem::Version.new('1.2.0') then
+      s.add_development_dependency(%q<rake>, ["~> 0.8.7"])
+      s.add_development_dependency(%q<rcov>, ["~> 0.9.8"])
+      s.add_development_dependency(%q<rr>, ["~> 0.10.11"])
+      s.add_development_dependency(%q<rspec>, ["~> 2.0.0"])
+      s.add_runtime_dependency(%q<eventmachine>, [">= 0"])
+      s.add_runtime_dependency(%q<heroku>, ["~> 1.9"])
+      s.add_runtime_dependency(%q<rack>, ["~> 1.0"])
+    else
+      s.add_dependency(%q<rake>, ["~> 0.8.7"])
+      s.add_dependency(%q<rcov>, ["~> 0.9.8"])
+      s.add_dependency(%q<rr>, ["~> 0.10.11"])
+      s.add_dependency(%q<rspec>, ["~> 2.0.0"])
+      s.add_dependency(%q<eventmachine>, [">= 0"])
+      s.add_dependency(%q<heroku>, ["~> 1.9"])
+      s.add_dependency(%q<rack>, ["~> 1.0"])
+    end
+  else
+    s.add_dependency(%q<rake>, ["~> 0.8.7"])
+    s.add_dependency(%q<rcov>, ["~> 0.9.8"])
+    s.add_dependency(%q<rr>, ["~> 0.10.11"])
+    s.add_dependency(%q<rspec>, ["~> 2.0.0"])
+    s.add_dependency(%q<eventmachine>, [">= 0"])
+    s.add_dependency(%q<heroku>, ["~> 1.9"])
+    s.add_dependency(%q<rack>, ["~> 1.0"])
+  end
+end
+

lib/heroku/autoscale.rb

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+require "eventmachine"
+require "heroku"
+require "rack"
+
+module Heroku
+  class Autoscale
+
+    VERSION = "0.1"
+
+    attr_reader :app, :options, :last_scaled
+
+    def initialize(app, options={})
+      @app = app
+      @options = default_options.merge(options)
+      @last_scaled = Time.now - 60
+      check_options!
+    end
+
+    def call(env)
+      if options[:defer]
+        EventMachine.defer { autoscale(env) }
+      else
+        autoscale(env)
+      end
+
+      app.call(env)
+    end
+
+private ######################################################################
+
+    def autoscale(env)
+      original_dynos = dynos = current_dynos
+      wait = queue_wait(env)
+
+      dynos -= 1 if wait <= options[:queue_wait_low]
+      dynos += 1 if wait >= options[:queue_wait_high]
+
+      dynos = options[:min_dynos] if dynos < options[:min_dynos]
+      dynos = options[:max_dynos] if dynos > options[:max_dynos]
+      dynos = 1 if dynos < 1
+
+      set_dynos(dynos) if dynos != original_dynos
+    end
+
+    def check_options!
+      errors = []
+      errors << "Must supply :username to Heroku::Autoscale" unless options[:username]
+      errors << "Must supply :password to Heroku::Autoscale" unless options[:password]
+      errors << "Must supply :app_name to Heroku::Autoscale" unless options[:app_name]
+      raise errors.join(" / ") unless errors.empty?
+    end
+
+    def current_dynos
+      heroku.info(options[:app_name])[:dynos].to_i
+    end
+
+    def default_options
+      {
+        :min_dynos       => 1,
+        :max_dynos       => 1,
+        :queue_wait_high => 5000, # milliseconds
+        :queue_wait_low  => 0,    # milliseconds
+        :min_frequency   => 10    # seconds
+      }
+    end
+
+    def heroku
+      @heroku ||= Heroku::Client.new(options[:username], options[:password])
+    end
+
+    def queue_wait(env)
+      env["HTTP_X_HEROKU_QUEUE_WAIT_TIME"]
+    end
+
+    def set_dynos(count)
+      return if (Time.now - last_scaled) < options[:min_frequency]
+      heroku.set_dynos(options[:app_name], count)
+      @last_scaled = Time.now
+    end
+
+  end
+end

spec/heroku/autoscale_spec.rb

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+require "spec_helper"
+require "heroku/autoscale"
+
+describe Heroku::Autoscale do
+
+  include Rack::Test::Methods
+
+  def noop
+    lambda {}
+  end
+
+  describe "option validation" do
+    it "requires username" do
+      lambda { Heroku::Autoscale.new(noop) }.should raise_error(/Must supply :username/)
+    end
+
+    it "requires password" do
+      lambda { Heroku::Autoscale.new(noop) }.should raise_error(/Must supply :password/)
+    end
+
+    it "requires app_name" do
+      lambda { Heroku::Autoscale.new(noop) }.should raise_error(/Must supply :app_name/)
+    end
+  end
+
+  describe "with valid options" do
+    let(:app) do
+      Heroku::Autoscale.new noop,
+        :defer => false,
+        :username => "test_username",
+        :password => "test_password",
+        :app_name => "test_app_name",
+        :min_dynos       => 1,
+        :max_dynos       => 10,
+        :queue_wait_low  => 10,
+        :queue_wait_high => 100,
+        :min_frequency   => 10
+    end
+
+    it "scales up" do
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name") { { :dynos => 1 } }
+      heroku.set_dynos("test_app_name", 2)
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 101 })
+    end
+
+    it "scales down" do
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name") { { :dynos => 3 } }
+      heroku.set_dynos("test_app_name", 2)
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 9 })
+    end
+
+    it "wont go below one dyno" do
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name") { { :dynos => 1 } }
+      heroku.set_dynos.times(0)
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 9 })
+    end
+
+    it "respects max dynos" do
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name") { { :dynos => 10 } }
+      heroku.set_dynos.times(0)
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 101 })
+    end
+
+    it "respects min dynos" do
+      app.options[:min_dynos] = 2
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name") { { :dynos => 2 } }
+      heroku.set_dynos.times(0)
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 9 })
+    end
+
+    it "doesnt flap" do
+      heroku = mock(Heroku::Client)
+      heroku.info("test_app_name").times(any_times) { { :dynos => 5 } }
+      heroku.set_dynos.with_any_args.once
+
+      mock(app).heroku.times(any_times) { heroku }
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 9 })
+      app.call({ "HTTP_X_HEROKU_QUEUE_WAIT_TIME" => 9 })
+    end
+  end
+
+end

spec/spec_helper.rb

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+require "rubygems"
+require "rack/test"
+require "rspec"
+
+$:.unshift "lib"
+
+Rspec.configure do |config|
+  config.color_enabled = true
+  config.mock_with :rr
+end