How to stop a background thread in Sinatra once the connection is closed

I'm trying to consume the twitter streaming API with Sinatra and give users real-time updates when they search for a keyword.

require 'sinatra'
require 'eventmachine'
require 'em-http'
require 'json'

STREAMING_URL = 'https://stream.twitter.com/1/statuses/sample.json'

get '/' do
  stream(:keep_open) do |out|
    http = EM::HttpRequest.new(STREAMING_URL).get :head => { 'Authorization' => [ 'USERNAME', 'PASS' ] }
    buffer = ""
    http.stream do |chunk|
      puts "still chugging"
      buffer += chunk
      while line = buffer.slice!(/.+\r?\n/)
        tweet = JSON.parse(line)
        unless tweet.length == 0 or tweet['user'].nil?
            out << "<p><b>#{tweet['user']['screen_name']}</b>开发者_如何学运维;: #{tweet['text']}</p>" 
        end
      end
    end
  end
end

I want the processing of the em-http-request stream to stop if the user closes the connection. Does anyone know how to do this?

---

Eric's answer was close, but what it does is closing the response body (not the client connection, btw) once your twitter stream closes, which normally never happens. This should work:

require 'sinatra/streaming' # gem install sinatra-contrib
# ...

get '/' do
  stream(:keep_open) do |out|
    # ...
    out.callback { http.conn.close_connection }
    out.errback { http.conn.close_connection }
  end
end

---

I'm not quite familiar with the Sinatra stream API yet, but did you try this?

http.callback { out.close }