Question

I have the following code (just as a test) and I want to create an HTTP proxy using EventMachine. The code below is an example on the es-proxy GitHub page. However, when I run this and open up a website that has a moderate amount of images, the images start loading incorrectly. What I mean by this is that some images are loaded twice or if I request my icon for the navigation bar, I instead get the profile picture. This is especially evident if I refresh the page a few times.

It seems that the responses do not correspond to the matching request; causing everything to be jumbled. However, I’m not sure why this is. The code below seems simple enough for this to not be a problem.

require 'rubygems'
require 'em-proxy'
require 'http/parser' # gem install http_parser.rb
require 'uuid'        # gem install uuid

# > ruby em-proxy-http.rb
# > curl --proxy localhost:9889 www.google.com

host = "0.0.0.0"
port = 9889
puts "listening on #{host}:#{port}..."

Proxy.start(:host => host, :port => port) do |conn|

  @p = Http::Parser.new
  @p.on_headers_complete = proc do |h|
    session = UUID.generate
    puts "New session: #{session} (#{h.inspect})"

    host, port = h['Host'].split(':')
    conn.server session, :host => host, :port => (port || 80)
    conn.relay_to_servers @buffer

    @buffer = ''
  end

  @buffer = ''

  conn.on_connect do |data,b|
    puts [:on_connect, data, b].inspect
  end

  conn.on_data do |data|
    @buffer << data
    @p << data

    data
  end

  conn.on_response do |backend, resp|
    #puts [:on_response, backend, resp].inspect
    resp
  end

  conn.on_finish do |backend, name|
    puts [:on_finish, name].inspect
  end
end

Update

I believe I have insight as to what is happening but, still no way of solving my problem. I am creating a server for each request and when I relay my requests I have multiple servers. Then in the on response I should only be returning the response if it is from the correct server. However, I don’t have a way to correlate this as of yet.

Answer 1

Here a proper response:

Try removing every puts in the example so the main loop can concentrate on doing the actual network I/O, it works for me like that.
I think there may be some kind of timeout playing behind this, maybe the client does not wait long enough for the full answer to come back while the server is stuck outputing text to the console.

That’s the downside of using an event reactor, you have to make sure nothing blocks it.