async_sinatra requests crash silently with em-http. How do I fix this?

Question

I have the following code:

require 'rubygems'
require 'eventmachine'
require 'em-http'
require 'sinatra/base'
require 'sinatra/async'

class Api < Sinatra::Base
  register Sinatra::Async

  aget '/1' do
      EventMachine.run {
         http = EventMachine::HttpRequest.new( "http://www.google.com").get(:timeout => 5)
         http.callback { puts "h2" ;ret_val = http.response; EventMachine.stop}
         http.errback {puts "was h2ere1" ;ret_val = nil; EventMachine.stop}
       }
       body "done processing 1"
  end

  aget '/2' do
       body "done processing 2"
  end

end

When I issue the following, it works well:

 curl http://localhost:3000/2

But, when I issue the following request, it prints "h2" and the application silently quits:

 curl http://localhost:3000/1

Any help will be appreciated. Thanks!

Answer 1

If your web server (Eg. thin) is based on EventMachine, then the EventMachine.stop line will actually stop the webserver as well as the EventMachine instance created by EventMachine.run.

I can't find a way to stop nested EventMachines like this. My advice - use Weary or another non-blocking HTTP request library.

Answer 2

Sinatra::Async provides it's own body helper that needs to be called from within the EventMachine loop. Also worth noting: if you're running Sinatra through Thin, you shouldn't call EM.run explicitly, as Sinatra is already operating within an EventMachine loop.