mongo_auth.rb

class MongoAuth 
  include Goliath::Rack::AsyncMiddleware
  include Goliath::Validation
  include Goliath::Rack::Validator
  
  class MissingApikeyError     < BadRequestError   ; end
  class DatabaseSaveError     < BadRequestError   ; end
  class RateLimitExceededError < ForbiddenError    ; end
  class UserIDMismatchError     < UnauthorizedError ; end

  def initialize(app, db_name)
    @app = app
    @db_name = db_name
  end
  

  def call(env)
    @env = env
    @db = env.config[@db_name]
    env.trace('auth pre-process')
    
    if requires_authentication?
    
      if auth_key = read_authorization_header
        lookup_auth_token(auth_key) #async call to db happens here
      else
        raise MissingApikeyError, "can't read auth key from header"
      end
      
    end
    
    super(env)
  end


  private 
  
  
  def requires_authentication?
    @env[Goliath::Request::REQUEST_METHOD] =~ /(POST|PUT)/ unless Goliath.env.to_s == "test" #returns true on POST, false otherwise
  end

  def is_get_request?
    @env[Goliath::Request::REQUEST_METHOD] == 'GET'
  end


  def read_authorization_header
    if @env['async-headers']['Authorization'] =~ /^FTAuth\s(.*)/
      auth_key = $1
    else
      false
    end
  end

  # check the database - this is where the async call happens
  
  def lookup_auth_token(auth_key)
    first('users', { :authentication_token => auth_key }) do |res|
      @env.trace('auth responded')
      if res
        @env['user_id']= res['_id']
        @env['authenticated'] = true 
      else
        @env['user_id'] = 0
        @env['authenticated'] = false
      end
    end
  end


  def db
    @db
  end

  def find(collection, selector={}, opts={}, &block)
    db.collection(collection).find(selector, opts) do |result|
      yield result
    end
  end

  def first(collection, selector={}, opts={}, &block)
    opts[:limit] = 1
    find(collection, selector, opts) do |result|
      yield result.first
    end
  end

end

result.log

Tracers for thread 1
--------------------------------------------
1-0 :: do login done in 0.200142
[:object_id, "4e0e21a7df715b0930000017"][:return, "User saved successfully"]
1-2 :: change username done in 0.926572
--
[:error, "Invalid auth token / token not found"]
1-5 :: change username done in 0.020906
--
[:error, "Invalid auth token / token not found"]
1-8 :: change username done in 0.021837
--
[:error, "Invalid auth token / token not found"]
1-11 :: change username done in 0.022213
--
[:error, "Invalid auth token / token not found"]
1-14 :: change username done in 0.022441
--
[:object_id, "4e0e21a7df715b0930000017"][:return, "User saved successfully"]
1-17 :: change username done in 0.950399