Issue: Running into `URLError <urlopen error The write operation timed out>` when uploading CSV file through API

Description

Hi Folks, I am running into URLError <urlopen error The write operation timed out> when uploading CSV file of large size (~200MB). The file is eventually uploaded into slack, yet the code breaks with that error. Can anyone explain why that’s happening?

What type of issue is this? (place an `x` in one of the `[ ]`)

bug
enhancement (feature request)
question
documentation related
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Requirements (place an `x` in each of the `[ ]`)

I’ve read and understood the Contributing guidelines and have done my best effort to follow them.
I’ve read and agree to the Code of Conduct.
I’ve searched for any related issues and avoided creating a duplicate issue.

Bug Report

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Reproducible in:

slackclient version: 2.7.1

python version: 3.6.5

OS version(s): macOS 10.14.6

Steps to reproduce:

Create a webclient with the necessary permissions
Create/Load a dataframe with size ~200MB as df (the one I tested with had a shape of (5400000, 6))
use the files_upload method to load files using the command as shown web_client.files_upload(channels = 'CXXXXXXXXXX', initial_comment="something", content=df.to_csv(index=False), filename="test.csv")

Expected result:

What you expected to happen: File sent with response ‘ok’:true

Actual result:

What actually happened:

---------------------------------------------------------------------------
timeout                                   Traceback (most recent call last)
~/anaconda3/lib/python3.6/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1317                 h.request(req.get_method(), req.selector, req.data, headers,
-> 1318                           encode_chunked=req.has_header('Transfer-encoding'))
   1319             except OSError as err: # timeout error

~/anaconda3/lib/python3.6/http/client.py in request(self, method, url, body, headers, encode_chunked)
   1238         """Send a complete request to the server."""
-> 1239         self._send_request(method, url, body, headers, encode_chunked)
   1240

~/anaconda3/lib/python3.6/http/client.py in _send_request(self, method, url, body, headers, encode_chunked)
   1284             body = _encode(body, 'body')
-> 1285         self.endheaders(body, encode_chunked=encode_chunked)
   1286

~/anaconda3/lib/python3.6/http/client.py in endheaders(self, message_body, encode_chunked)
   1233             raise CannotSendHeader()
-> 1234         self._send_output(message_body, encode_chunked=encode_chunked)
   1235

~/anaconda3/lib/python3.6/http/client.py in _send_output(self, message_body, encode_chunked)
   1064                         + b'\r\n'
-> 1065                 self.send(chunk)
   1066

~/anaconda3/lib/python3.6/http/client.py in send(self, data)
    985         try:
--> 986             self.sock.sendall(data)
    987         except TypeError:

~/anaconda3/lib/python3.6/ssl.py in sendall(self, data, flags)
    971                 while count < amount:
--> 972                     v = self.send(byte_view[count:])
    973                     count += v

~/anaconda3/lib/python3.6/ssl.py in send(self, data, flags)
    940                     self.__class__)
--> 941             return self._sslobj.write(data)
    942         else:

~/anaconda3/lib/python3.6/ssl.py in write(self, data)
    641         """
--> 642         return self._sslobj.write(data)
    643

timeout: The write operation timed out
During handling of the above exception, another exception occurred:                                                                                                                                                                                                     [74/639]

URLError                                  Traceback (most recent call last)
<ipython-input-16-e4c541ebf2f5> in <module>
----> 1 web_client.files_upload(channels = 'CXXXXXXXXXX', initial_comment="something", content=df.to_csv(index=False), filename="test.csv")

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/client.py in files_upload(self, file, content, **kwargs)
   1217         data = kwargs.copy()
   1218         data.update({"content": content})
-> 1219         return self.api_call("files.upload", data=data)
   1220
   1221     def groups_archive(self, *, channel: str, **kwargs) -> Union[Future, SlackResponse]:

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/base_client.py in api_call(self, api_method, http_verb, files, data, params, json, headers, auth)
    213                 return self._event_loop.run_until_complete(future)
    214         else:
--> 215             return self._sync_send(api_url=api_url, req_args=req_args)
    216
    217     def _get_url(self, api_method):

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/base_client.py in _sync_send(self, api_url, req_args)
    346             files=files,
    347             json_body=_json,
--> 348             additional_headers=headers,
    349         )
    350

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/base_client.py in _urllib_api_call(self, token, url, query_params, json_body, body_params, files, additional_headers)
    448                 url = f"{url}&{q}" if "?" in url else f"{url}?{q}"
    449
--> 450             response = self._perform_urllib_http_request(url=url, args=request_args)
    451             if response.get("body", None):
    452                 response_body_data: dict = json.loads(response["body"])

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/base_client.py in _perform_urllib_http_request(self, url, args)
    579         except Exception as err:
    580             self._logger.error(f"Failed to send a request to Slack API server: {err}")
--> 581             raise err
    582
    583     def _build_urllib_request_headers(

~/.virtualenvs/scratch/lib/python3.6/site-packages/slack/web/base_client.py in _perform_urllib_http_request(self, url, args)
    560
    561                 resp: HTTPResponse = urlopen(
--> 562                     req, context=self.ssl, timeout=self.timeout
    563                 )
    564                 charset = resp.headers.get_content_charset()

~/anaconda3/lib/python3.6/urllib/request.py in urlopen(url, data, timeout, cafile, capath, cadefault, context)
    221     else:
    222         opener = _opener
--> 223     return opener.open(url, data, timeout)
    224
    225 def install_opener(opener):

~/anaconda3/lib/python3.6/urllib/request.py in open(self, fullurl, data, timeout)
    524             req = meth(req)
    525
--> 526         response = self._open(req, data)
    527
    528         # post-process response
~/anaconda3/lib/python3.6/urllib/request.py in _open(self, req, data)
    542         protocol = req.type
    543         result = self._call_chain(self.handle_open, protocol, protocol +
--> 544                                   '_open', req)
    545         if result:
    546             return result

~/anaconda3/lib/python3.6/urllib/request.py in _call_chain(self, chain, kind, meth_name, *args)
    502         for handler in handlers:
    503             func = getattr(handler, meth_name)
--> 504             result = func(*args)
    505             if result is not None:
    506                 return result

~/anaconda3/lib/python3.6/urllib/request.py in https_open(self, req)
   1359         def https_open(self, req):
   1360             return self.do_open(http.client.HTTPSConnection, req,
-> 1361                 context=self._context, check_hostname=self._check_hostname)
   1362
   1363         https_request = AbstractHTTPHandler.do_request_

~/anaconda3/lib/python3.6/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1318                           encode_chunked=req.has_header('Transfer-encoding'))
   1319             except OSError as err: # timeout error
-> 1320                 raise URLError(err)
   1321             r = h.getresponse()
   1322         except:

URLError: <urlopen error The write operation timed out>