Question

I have a Sinatra class in a Rails project. It uses eventmachine and async_sinatra to make asynchronous calls to external sites. I’d like to write to a session object (ideally, the same one that Rails is using), but so far I can only:

• write to a separate session object from Rails’ (by default, Sinatra names its session something different from Rails)
• write to the same session for synchronous calls only

When I make asynchronous calls, sessions written in the async_sinatra code don’t get pushed out to the client machine. I suspect one of two things is happening:

• The header has already been sent to the client and the local variable storing the session (in Sinatra) will be flushed out at the end of the action. The client would never see a request from the server to save this data to a cookie.

• The header is being sent to the client, but Rails immediate sends another, instructing the client to write to the cookie what Rails has stored in its session variable, overwriting what Sinatra wrote.

Either way, I’d like to just get simple session functionality in both Sinatra and Rails. An explanation of what I’m doing wrong would also be nice 🙂

A full working copy of the code is on github, but I believe the problem is specifically in this code:

class ExternalCall < Sinatra::Base
  use ActionDispatch::Session::CookieStore
  register Sinatra::Async  

  get '/sinatra/local' do
    session[:demo] = "sinatra can write to Rails' session"
  end

  aget '/sinatra/goog' do
    session[:async_call]="async sinatra calls cannot write to Rails' session"
    make_async_req :get, "http://www.google.com/" do |http_callback|
      if http_callback
        session[:em_callback] = "this also isn't saving for me" 
      else
        headers 'Status' => '422'
      end
      async_schedule { redirect '/' }

    end
  end


  helpers do
    def make_async_req(method, host, opts={}, &block)
      opts[:head] = { 'Accept' => 'text/html', 'Connection' => 'keep-alive' }
      http = EM::HttpRequest.new(host)
      http = http.send(method, {:head => opts[:head], :body => {}, :query => {}})
      http.callback &block
    end
  end
end

EDIT 7/15:

Changed code on Github to include Async-Rack. Async-sinatra can write to sessions when they are not shared with Rails. Compare the master and segmented_sessions branches for behavior difference. (Or on the master branch, change use ActionDispatch::Session::CookieStore to enable :sessions)

Answer 1

This is because async_sinatra uses throw :async by default, effectively skipping the session middleware logic for storing stuff. You could override async_response like that:

helpers do
  def async_response
    [-1, {}, []]
  end
end