Getting EventMachine::ConnectionNotBound error with 0.2.10

[myronmarston]

em_http_example.rb:

require 'rubygems'
gem 'em-http-request', '0.2.10'
require 'em-http'

def make_http_request(url)
  EventMachine.run do
    http = EventMachine::HttpRequest.new(url).get
    http.callback { EventMachine.stop; return http }
  end 
end

make_http_request("http://example.com/")

Output:

ruby-1.8.7-p299 ➜  ~  ruby em_http_example.rb 
/Users/mmarston/.rvm/gems/ruby-1.8.7-p299/gems/eventmachine-0.12.10/lib/eventmachine.rb:1425:in `event_callback': recieved ConnectionUnbound for an unknown signature: 2 (EventMachine::ConnectionNotBound)
        from /Users/mmarston/.rvm/gems/ruby-1.8.7-p299/gems/eventmachine-0.12.10/lib/eventmachine.rb:263:in `release_machine'
        from /Users/mmarston/.rvm/gems/ruby-1.8.7-p299/gems/eventmachine-0.12.10/lib/eventmachine.rb:263:in `run'
        from em_http_example.rb:6:in `make_http_request'
        from em_http_example.rb:12

[igrigorik]

Hmm, well I'm not sure that the code makes sense the way it is setup currently. You can't call return from a callback like that (unless I'm missing something at the moment). If you remove the return statement, everything will work just fine. If you need ~ blocking API, you should take a look at em-synchrony.

[myronmarston]

I'm actually not using em-http-request in any of my projects; I just want to make sure VCR supports it. All of the other HTTP libraries supported by VCR are synchronous, and use the same shared specs, with each implementing #make_http_request differently based on the libraries API, so I wrote the em-http-request implementation of #make_http_request to be synchronous, even though you would never use it that way.

Using return in a block is a bit counterintuitive, but it's standard ruby--it causes the lexically enclosing method to return (in this case #make_http_request), and it worked just fine on em-http-request 0.2.7.

I did a git bisect, and it appears that this commit is the first commit where this no longer worked.

I can rewrite the method like this, and it seems to work fine:

def make_http_request(url)
  http = nil
  EventMachine.run do
    http = EventMachine::HttpRequest.new(url).get
    http.callback { EventMachine.stop }
  end 
  http
end

So I can work around it.

[igrigorik]

Right, I see. It's not obvious to me why the redirect logic would be causing this behavior. I'll take a closer look, but since the above works, we ok to close the ticket?

[myronmarston]

Yep, thanks.