问题

简述

使用 python requests 上传文件时, 报
OverflowError: string longer than 2147483647 bytes 错误.

detail

问题代码

    data = {}
    with open("bigfile", "rb") as f:
        r = requests.post(PUBLISH_URL, data=data, files={"xxx": f})

traceback

Traceback (most recent call last):
  File "test.py", line 52, in <module>
    main()
  File "test.py", line 49, in main
    publish()
  File "test.py", line 41, in publish
    r = requests.post(PUBLISH_URL, data=cfg, files={file_key: ("./test.apk", f)})
  File "/usr/local/lib/python2.7/dist-packages/requests/api.py", line 116, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/adapters.py", line 449, in send
    timeout=timeout
  File "/usr/local/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 600, in urlopen
    chunked=chunked)
  File "/usr/local/lib/python2.7/dist-packages/urllib3/connectionpool.py", line 354, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/lib/python2.7/httplib.py", line 1057, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib/python2.7/httplib.py", line 1097, in _send_request
    self.endheaders(body)
  File "/usr/lib/python2.7/httplib.py", line 1053, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python2.7/httplib.py", line 897, in _send_output
    self.send(msg)
  File "/usr/lib/python2.7/httplib.py", line 873, in send
    self.sock.sendall(data)
  File "/usr/lib/python2.7/ssl.py", line 743, in sendall
    v = self.send(data[count:])
  File "/usr/lib/python2.7/ssl.py", line 709, in send
    v = self._sslobj.write(data)
OverflowError: string longer than 2147483647 bytes

分析过程

requests 将 file obj 全部读入内存了

没想到 requests 的实现这么粗暴, 直接 file.read(), 实际也是如此, 发送大文件时, 内存快速上涨. 代码如下:
requests/models.py

    @staticmethod
    def _encode_files(files, data):
        """Build the body for a multipart/form-data request.

        Will successfully encode files when passed as a dict or a list of
        tuples. Order is retained if data is a list of tuples but arbitrary
        if parameters are supplied as a dict.
        The tuples may be 2-tuples (filename, fileobj), 3-tuples (filename, fileobj, contentype)
        or 4-tuples (filename, fileobj, contentype, custom_headers).
        """
        if (not files):
            raise ValueError("Files must be provided.")
        elif isinstance(data, basestring):
            raise ValueError("Data must not be a string.")

        new_fields = []
        fields = to_key_val_list(data or {})
        files = to_key_val_list(files or {})

        for field, val in fields:
            if isinstance(val, basestring) or not hasattr(val, '__iter__'):
                val = [val]
            for v in val:
                if v is not None:
                    # Don't call str() on bytestrings: in Py3 it all goes wrong.
                    if not isinstance(v, bytes):
                        v = str(v)

                    new_fields.append((field.decode('utf-8') if isinstance(field, bytes) else field,
                         v.encode('utf-8') if isinstance(v, str) else v))

        for (k, v) in files:
            # support for explicit filename
            ft = None
            fh = None
            if isinstance(v, (tuple, list)):
                if len(v) == 2:
                    fn, fp = v
                elif len(v) == 3:
                    fn, fp, ft = v
                else:
                    fn, fp, ft, fh = v
            else:
                fn = guess_filename(v) or k
                fp = v

            if isinstance(fp, (str, bytes, bytearray)):
                fdata = fp
            elif hasattr(fp, 'read'):
                fdata = fp.read() # 这里将所有文件都读入内存
            elif fp is None:
                continue
            else:
                fdata = fp

            rf = RequestField(name=k, data=fdata, filename=fn, headers=fh)
            rf.make_multipart(content_type=ft)
            new_fields.append(rf)

        body, content_type = encode_multipart_formdata(new_fields)

        return body, content_type

官方文档推荐使用 requests-toolbelt

https://2.python-requests.org…

In the event you are posting a very large file as a multipart/form-data request, you may want to stream the request. By default, requests does not support this, but there is a separate package which does – requests-toolbelt. You should read the toolbelt’s documentation for more details about how to use it.

使用 requests-toolbelt 的写法

from requests_toolbelt import MultipartEncoder

    data = {}
    with open("bigfile", "rb") as f:
        data["xxx"] = ("filename", f)
        m = MultipartEncoder(fields=data)
        r = requests.post(PUBLISH_URL, data=m, headers={'Content-Type': m.content_type})

总结

requests 的发送文件的实现十分粗暴, 会直接读全部文件内容到内存再 sign, ssl sign 大于 2GB 会报错, 官方文档推荐使用 requests-toolbelt 上传大文件.
分块上传当然也是一个方案 (如果服务器支持).