Python的Tornado框架的异步任务与AsyncHTTPClient

@router.Route('/api/v2/account/upload')
class ApiAccountUploadHandler(helper.BaseHandler):
  @tornado.gen.coroutine
  @helper.token_require
  def post(self, *args, **kwargs):
    upload_type = self.get_argument('type', None)

    files_body = self.request.files['file']

    new_file = 'upload/new_pic.jpg'
    new_file_name = 'new_pic.jpg'

    # 写入文件
    with open(new_file, 'w') as w:
      w.write(file_['body'])

    logging.info('user {} upload {}'.format(user_id, new_file_name))

    # 异步请求 上传图片
    with open(new_file, 'rb') as f:
      files = [('image', new_file_name, f.read())]

    fields = (('api_key', KEY), ('api_secret', SECRET))

    content_type, body = encode_multipart_formdata(fields, files)

    headers = {"Content-Type": content_type, 'content-length': str(len(body))}
    request = tornado.httpclient.HTTPRequest(config.OCR_HOST,
                         method="POST", headers=headers, body=body, validate_cert=False)

    response = yield tornado.httpclient.AsyncHTTPClient().fetch(request)

def encode_multipart_formdata(fields, files):
  """
  fields is a sequence of (name, value) elements for regular form fields.
  files is a sequence of (name, filename, value) elements for data to be
  uploaded as files.
  Return (content_type, body) ready for httplib.HTTP instance
  """
  boundary = '----------ThIs_Is_tHe_bouNdaRY_$'
  crlf = '\r\n'
  l = []
  for (key, value) in fields:
    l.append('--' + boundary)
    l.append('Content-Disposition: form-data; name="%s"' % key)
    l.append('')
    l.append(value)
  for (key, filename, value) in files:
    filename = filename.encode("utf8")
    l.append('--' + boundary)
    l.append(
        'Content-Disposition: form-data; name="%s"; filename="%s"' % (
          key, filename
        )
    )
    l.append('Content-Type: %s' % get_content_type(filename))
    l.append('')
    l.append(value)
  l.append('--' + boundary + '--')
  l.append('')
  body = crlf.join(l)
  content_type = 'multipart/form-data; boundary=%s' % boundary
  return content_type, body


def get_content_type(filename):
  import mimetypes

  return mimetypes.guess_type(filename)[0] or 'application/octet-stream'

对比上述的用法，上传图片仅仅是多了一个图片的编码。将图片的二进制数据按照multipart 方式编码。编码的同时，还需要把传递的相关的字段处理好。相比之下，使用requests 的方式则非常简单：

files = {}
f = open('/Users/ghost/Desktop/id.jpg')
files['image'] = f
data = dict(api_key='KEY', api_secret='SECRET')
resp = requests.post(url, data=data, files=files)
f.close()
print resp.status_Code