Adding the functional middleware

Gemfile

@@ -1,4 +1,3 @@
 source :rubygems
 
-gem "rake"
 gemspec

Gemfile.lock

@@ -2,13 +2,12 @@ PATH
   remote: .
   specs:
     heroscale (0.0.1)
-      rack (~> 1.0)
 
 GEM
   remote: http://rubygems.org/
   specs:
     diff-lcs (1.1.2)
-    rack (1.2.1)
+    json (1.4.6)
     rake (0.8.7)
     rspec (2.1.0)
       rspec-core (~> 2.1.0)
@@ -24,6 +23,6 @@ PLATFORMS
 
 DEPENDENCIES
   heroscale!
-  rack (~> 1.0)
-  rake
+  json
+  rake (~> 0.8.7)
   rspec (~> 2.0)

Rakefile

@@ -39,5 +39,4 @@ Rake::RDocTask.new do |rdoc|
   rdoc.rdoc_files.include("lib/**/*.rb")
 end
 
-
 task :default => :spec

heroscale.gemspec

@@ -27,8 +27,9 @@ Gem::Specification.new do |s|
     "README.md"
   ]
 
-  s.add_runtime_dependency 'rack', '~> 1.0'
+  s.add_development_dependency "json"
   s.add_development_dependency "rspec", "~> 2.0"
+  s.add_development_dependency 'rake',      '~> 0.8.7'
 end
 
 

lib/heroscale.rb

@@ -0,0 +1,2 @@
+require 'heroscale/middleware'
+require 'heroscale/railtie' if defined?(Rails::Railtie)

lib/heroscale/middleware.rb

@@ -0,0 +1,29 @@
+module Heroscale
+
+  # simple Rack Middleware that adds a hook to return the heroku env info
+  class Middleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      if env["PATH_INFO"] == "/heroscale/status"
+        queue_wait_time = env['HTTP_X_HEROKU_QUEUE_WAIT_TIME']
+        queue_depth = env['HTTP_X_HEROKU_QUEUE_DEPTH']
+        dynos_in_use = env['HTTP_X_HEROKU_DYNOS_IN_USE']
+
+        if queue_wait_time and queue_depth and dynos_in_use
+          # format the response on heroku
+          res = %|{"heroku": true, "queue_wait_time": #{queue_wait_time.to_i}, "queue_depth": #{queue_depth.to_i}, "dynos_in_use": #{dynos_in_use.to_i}}|
+        else
+          res = %|{"heroku": false}|
+        end
+
+        [ 200, {'Content-Type' => 'application/json'}, res]
+      else
+        @app.call(env)
+      end
+    end
+
+  end
+end

spec/heroscale/middleware_spec.rb

@@ -0,0 +1,74 @@
+require "spec_helper"
+require "heroscale"
+
+require "json"
+
+describe Heroscale::Middleware do
+
+  # this is our original app (that the middleware is wrapping around)
+  let(:orig_app) do
+    lambda do |env|
+      [ 200, {'Content-Type' => 'application/json'}, "HELLO!"]
+    end
+  end
+
+  # this is our app with the middleware attached
+  let(:app) do
+    Heroscale::Middleware.new orig_app
+  end
+
+  def heroku_request(opts = {})
+    app.call({
+      'PATH_INFO' => '/heroscale/status',
+      'HTTP_X_HEROKU_QUEUE_WAIT_TIME' => (opts[:wait] || 100),
+      'HTTP_X_HEROKU_QUEUE_DEPTH' => (opts[:depth] || 0),
+      'HTTP_X_HEROKU_DYNOS_IN_USE' => (opts[:dynos] || 1)
+    })
+  end
+
+  context "when querying on a heroku instance" do
+    before(:each) do
+      @rack_response = heroku_request(:wait => 100, :depth => 5, :dynos => 12)
+      @json = JSON.parse(@rack_response.last)
+    end
+
+    it "should return the 'heroku' field that tells that we're on heroku" do
+      @json["heroku"].should == true
+    end
+
+    it "should return the 'queue_wait_time' field that tells us the queue wait time" do
+      @json["queue_wait_time"].should == 100
+    end
+
+    it "should return the 'queue_depth' field that tells us the current queue depth" do
+      @json["queue_depth"].should == 5
+    end
+
+    it "should return the 'dynos_in_use' field that tells us the current heroku dynos in use" do
+      @json["dynos_in_use"].should == 12
+    end
+
+  end
+
+  context "when not quering the status link" do
+    it "should return the original app's response" do
+      app.call({}).last.should == "HELLO!"
+      app.call({"PATH_INFO" => "/"}).last.should == "HELLO!"
+      app.call({"PATH_INFO" => "/heroscale/"}).last.should == "HELLO!"
+      app.call({"PATH_INFO" => "/heroscale/status2"}).last.should == "HELLO!"
+    end
+
+  end
+
+  context "when query while not on a heroku instance" do
+    before(:each) do
+      @rack_response = app.call({"PATH_INFO" => "/heroscale/status"})
+      @json = JSON.parse(@rack_response.last)
+    end
+
+    it "should return the 'heroku' field telling use we're not on heroku" do
+      @json["heroku"].should == false
+    end
+  end
+
+end

spec/spec_helper.rb

@@ -0,0 +1,8 @@
+require 'bundler/setup'
+require "rspec"
+
+$:.unshift "lib"
+
+Rspec.configure do |config|
+  config.color_enabled = true
+end