inner_request_in_rails.rb

# Oleg Andreev <[email protected]> Oct 16, 2009
#
# This demonstrates how to perform a request to the same Rails instance without hitting HTTP server.
# Note 1: this does not boot another Rails instance
# Note 2: this does not involve HTTP parsing
# Note 3: dispatch_unlocked and rack.multithread=true are used to prevent deadlock on a dispatch mutex,
#         NOT to make inner requests operate concurrently as one may think.
# Note 4: inner request is created by merging outer request with some HTTP headers and rack options.
#         This may probably lead to strange effects, so be aware of it. 
#         Perhaps, we shouldn't use outer request at all. I don't know.
class LocalDispatcher < ActionController::Dispatcher
  def get(path, request)
    env = request.env.merge({
      "REQUEST_METHOD" => "GET",
      "SCRIPT_NAME"    => "/",
      "PATH_INFO"      => path,
      "REQUEST_PATH"   => path,
      "REQUEST_URI"    => path,
      
      "rack.version"      => [1,0],
      "rack.url_scheme"   => (request.ssl? ? "https" : "http"),
      "rack.input"        => StringIO.new(''),
      "rack.errors"       => $stderr, 
      "rack.multithread"  => true, # we probably need this to avoid deadlocks
      "rack.multiprocess"	=> true,
      "rack.run_once"     => false
       
      # Rack environment spec:
      # http://rack.rubyforge.org/doc/SPEC.html
    })
    
    @request  = ActionController::RackRequest.new(env)
    @response = ActionController::RackResponse.new(@request)
    begin
      status, headers, body = dispatch_unlocked
    rescue Exception => e
      Rails.logger.error("OfflineDispatcher got an exception #{e}")
      raise e
    end
    # TODO: more error checks before returning body
    out = ""
    body.each do |chunk|
      out << chunk
    end
    out
  end

  # override dispatch_unlocked to avoid class reloading
  def dispatch_unlocked
    begin
      handle_request
    rescue Exception => exception
      failsafe_rescue exception
    end
  end
end



class OfflineArchivesController < ApplicationController
  
  def show
    page = get_path("/page/123")
    render :text => page
  end
  
  private
  
  def get_path(path)
    LocalDispatcher.new.get(path, request)
  end
  
end