Add Rack::GarbageCollector middleware

Calls GC.start after each request. This is a really simplistic
implementation but I've found it useful in debugging potential
memory leaks.

lib/rack/contrib.rb

@@ -8,6 +8,7 @@ def self.release
 
   autoload :BounceFavicon,              "rack/bounce_favicon"
   autoload :ETag,                       "rack/etag"
+  autoload :GarbageCollector,           "rack/garbagecollector"
   autoload :JSONP,                      "rack/jsonp"
   autoload :LighttpdScriptNameFix,      "rack/lighttpd_script_name_fix"
   autoload :Locale,                     "rack/locale"

lib/rack/garbagecollector.rb

@@ -0,0 +1,14 @@
+module Rack
+  # Forces garbage collection after each request.
+  class GarbageCollector
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      res = @app.call(env)
+      GC.start
+      res
+    end
+  end
+end

test/spec_rack_garbagecollector.rb

@@ -0,0 +1,12 @@
+require 'rack/mock'
+require 'rack/garbagecollector'
+
+context 'Rack::GarbageCollector' do
+
+  specify 'starts the garbage collector after each request' do
+    app = lambda { |env|
+      [200, {'Content-Type'=>'text/plain'}, ['Hello World']] }
+    Rack::GarbageCollector.new(app).call({})
+  end
+
+end