README.rdoc

If we can create a DeferredDispatcher that is safe and generic, spin-up won’t be a show-stopper, and any app can take advantage of it. Adding this to appengine-rack.rb means people won’t need an additional require, but we will be stuck with it.

I have a sample app here: mwrc-demo.appspot.com

When we have app with multiple map sections (see below) that all call the same dispatcher, will the instance variables still work the way we want?

appengine-rack lib appengine-rack.rb

module AppEngine
  module Rack

    # ...

    class DeferredDispatcher
      def initialize args
        @args = args
        @rack_request_counter = 0
        @rack_app = nil
      end

      def call env
        @rack_request_counter += 1
        if @rack_request_counter <= 1
          return redirect_or_error(env)
        else
          unless @rack_app
            require @args[:require]
            @rack_app = Object.module_eval(@args[:dispatch]).new
            if @args[:three_part]
              return redirect_or_error(env)
            end
          end
          return @rack_app.call(env)
        end
      end

      def redirect_or_error(env)
        if env["REQUEST_METHOD"].eql?("GET")
          redir_url = env["REQUEST_URI"] +
              (env["QUERY_STRING"].eql?("") ? "?" : "&") +
              "_spinup_=#{Time.now.to_i}"
          res = ::Rack::Response.new("*", 302)
          res["Location"] = redir_url
          res.finish
        else
          ::Rack::Response.new("Service Unavailable", 503).finish
        end
      end
    end

    # ...

  end
end

complex config.ru

require 'appengine-rack'
AppEngine::Rack.configure_app(
    :application => 'complex-app',
    :precompilation_enabled => true,
    :sessions_enabled => true,
    :version => "1")

AppEngine::Rack.app.resource_files.exclude :rails_excludes
ENV['RAILS_ENV'] = AppEngine::Rack.environment

#map '/admin' do
#  use AppEngine::Rack::AdminRequired
#  run AppEngine::Rack::DeferredDispatcher.new(
#     :require => File.expand_path('../config/environment', __FILE__),
#     :dispatch => 'ActionController::Dispatcher')
#end
#
#map '/' do
#  use AppEngine::Rack::LoginRequired
#  run AppEngine::Rack::DeferredDispatcher.new(
#     :require => File.expand_path('../config/environment', __FILE__),
#     :dispatch => 'ActionController::Dispatcher')
#end

deferred_dispatcher = AppEngine::Rack::DeferredDispatcher.new(
     :require => File.expand_path('../config/environment', __FILE__),
     :dispatch => 'ActionController::Dispatcher')

map '/admin' do
  use AppEngine::Rack::AdminRequired
  run deferred_dispatcher
end

map '/' do
  use AppEngine::Rack::LoginRequired
  run deferred_dispatcher
end

simple config.ru

require 'appengine-rack'
AppEngine::Rack.configure_app(
    :application => 'simple-app',
    :precompilation_enabled => true,
    :sessions_enabled => true,
    :version => "1")

AppEngine::Rack.app.resource_files.exclude :rails_excludes
ENV['RAILS_ENV'] = AppEngine::Rack.environment

run AppEngine::Rack::DeferredDispatcher.new(
    :require => File.expand_path('../config/environment', __FILE__),
    :dispatch => 'ActionController::Dispatcher')