title: Close connection with python tornado http client on each call
body: <p>I am using tornado python to execute non blocking hundreds of calls to an external proxy service.
  The external proxy service requires me to use a new connection on every call.</p>
  
  <p>I wrote the following:</p>
  
  <pre><code>config = {
          'proxy_host': 'host',
          'proxy_port': port
      }
  
  httpclient.AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")
  for url in urls:
      client = httpclient.AsyncHTTPClient(force_instance=True)
      client.fetch(url, callback=callback, headers=headers, **config)
  ioloop.IOLoop.instance().start()
  
     def handle_request()
         do_something()
         if io_counter == max_calls:
              ioloop.IOLoop.instance().stop()
  </code></pre>
  
  <p>However, the service claims that I am using the same connection.</p>
  
  <p>How can I use a different connection on each call?</p>