tornado curl http client CANNOT fetch binary file

Question

I want to fetch a Image(GIF format) from a website.So I use tornado in-build asynchronous http client to do it.My code is like the following:

import tornado.httpclient
import tornado.ioloop
import tornado.gen
import tornado.web

tornado.httpclient.AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")
http_client = tornado.httpclient.AsyncHTTPClient()

class test(tornado.web.RequestHandler):
    @tornado.gen.coroutine
    def get(self):
        content = yield http_client.fetch('http://www.baidu.com/img/bdlogo.gif')
        print('=====', type(content.body))

application = tornado.web.Application([
    (r'/', test)
    ])
application.listen(80)
tornado.ioloop.IOLoop.instance().start()

So when I visit the server it should fetch a gif file.However It catch a exception.

UnicodeDecodeError: 'utf-8' codec can't decode byte 0x81 in position 8: invalid start byte
ERROR:tornado.application:Uncaught exception GET / (127.0.0.1)
HTTPRequest(protocol='http', host='127.0.0.1', method='GET', uri='/', version='HTTP/1.1', remote_ip='127.0.0.1', headers={'Accept-Language': 'zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3', 'Accept-Encoding': 'gzip, deflate', 'Host': '127.0.0.1', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'User-Agent': 'Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130922 Firefox/17.0', 'Connection': 'keep-alive', 'Cache-Control': 'max-age=0', 'If-None-Match': '"da39a3ee5e6b4b0d3255bfef95601890afd80709"'})
Traceback (most recent call last):
  File "/usr/lib/python3.2/site-packages/tornado/web.py", line 1144, in _when_complete
    if result.result() is not None:
  File "/usr/lib/python3.2/site-packages/tornado/concurrent.py", line 129, in result
    raise_exc_info(self.__exc_info)
  File "<string>", line 3, in raise_exc_info
  File "/usr/lib/python3.2/site-packages/tornado/stack_context.py", line 302, in wrapped
    ret = fn(*args, **kwargs)
  File "/usr/lib/python3.2/site-packages/tornado/gen.py", line 550, in inner
    self.set_result(key, result)
  File "/usr/lib/python3.2/site-packages/tornado/gen.py", line 476, in set_result
    self.run()
  File "/usr/lib/python3.2/site-packages/tornado/gen.py", line 505, in run
    yielded = self.gen.throw(*exc_info)
  File "test.py", line 12, in get
    content = yield http_client.fetch('http://www.baidu.com/img/bdlogo.gif')
  File "/usr/lib/python3.2/site-packages/tornado/gen.py", line 496, in run
    next = self.yield_point.get_result()
  File "/usr/lib/python3.2/site-packages/tornado/gen.py", line 395, in get_result
    return self.runner.pop_result(self.key).result()
  File "/usr/lib/python3.2/concurrent/futures/_base.py", line 393, in result
    return self.__get_result()
  File "/usr/lib/python3.2/concurrent/futures/_base.py", line 352, in __get_result
    raise self._exception
tornado.curl_httpclient.CurlError: HTTP 599: Failed writing body (0 != 1024)
ERROR:tornado.access:500 GET / (127.0.0.1) 131.53ms

It seems to attempt to decode my binary file as UTF-8 text, which is unnecessary.IF I comment

tornado.httpclient.AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")

out, which will use a simple http client instead of pycurl, it works well.(It tell me that the type of "content" is bytes)

So if it return a bytes object, why it tries to decode it? I think the problems is the pycurl or the wrapper of pycurl in tornado, right?

My python version is 3.2.5, tornado 3.1.1, pycurl 7.19.

Thanks!

Answer 1

pycurl 7.19 doesn't support Python 3. Ubuntu (and possibly other Linux distributions) ship a modified version of pycurl that partially works with Python 3, but it doesn't work with Tornado (https://github.com/facebook/tornado/issues/671), and fails with an exception that looks like the one you're seeing here.

Until there's a new version of pycurl that officially supports Python 3 (or you use the change suggested in that Tornado bug report), I'm afraid you'll need to either go back to Python 2.7 or use Tornado's simple_httpclient instead.