在Python的Tornado框架中实现简单的在线代理的教程

# -*- coding: utf-8 -*-
#
# Copyright(c) 2011 Felinx Lee & http://feilong.me/
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
 
import logging
 
import tornado.httpserver
import tornado.ioloop
import tornado.options
import tornado.web
import tornado.httpclient
from tornado.web import HTTPError, asynchronous
from tornado.httpclient import HTTPRequest
from tornado.options import define, options
try:
  from tornado.curl_httpclient import CurlAsyncHTTPClient as AsyncHTTPClient
except ImportError:
  from tornado.simple_httpclient import SimpleAsyncHTTPClient as AsyncHTTPClient
 
define("port", default=8888, help="run on the given port", type=int)
define("api_protocol", default="http")
define("api_host", default="feilong.me")
define("api_port", default="80")
define("debug", default=True, type=bool)
 
class ProxyHandler(tornado.web.RequestHandler):
  @asynchronous
  def get(self):
    # enable API GET request when debugging
    if options.debug:
      return self.post()
    else:
      raise HTTPError(405)
 
  @asynchronous
  def post(self):
    protocol = options.api_protocol
    host = options.api_host
    port = options.api_port
 
    # port suffix
    port = "" if port == "80" else ":%s" % port
 
    uri = self.request.uri
    url = "%s://%s%s%s" % (protocol, host, port, uri)
 
    # update host to destination host
    headers = dict(self.request.headers)
    headers["Host"] = host
 
    try:
      AsyncHTTPClient().fetch(
        HTTPRequest(url=url,
              method="POST",
              body=self.request.body,
              headers=headers,
              follow_redirects=False),
        self._on_proxy)
    except tornado.httpclient.HTTPError, x:
      if hasattr(x, "response") and x.response:
        self._on_proxy(x.response)
      else:
        logging.error("Tornado signalled HTTPError %s", x)
 
  def _on_proxy(self, response):
    if response.error and not isinstance(response.error,
                       tornado.httpclient.HTTPError):
      raise HTTPError(500)
    else:
      self.set_status(response.code)
      for header in ("Date", "Cache-Control", "Server", "Content-Type", "Location"):
        v = response.headers.get(header)
        if v:
          self.set_header(header, v)
      if response.body:
        self.write(response.body)
      self.finish()
 
def main():
  tornado.options.parse_command_line()
  application = tornado.web.Application([
    (r"/.*", ProxyHandler),
  ])
  http_server = tornado.httpserver.HTTPServer(application)
  http_server.listen(options.port)
  tornado.ioloop.IOLoop.instance().start()
 
if __name__ == "__main__":
  main()