[New-bugs-announce] [issue41345] Remote end closed connection without response

[Michal Arbet]

New submission from Michal Arbet <michal.arbet at ultimum.io>:

Hi,

I'm not sure if this is really python bug, but I hope that you can check the issue.

Issue is that from time to time i'm getting exception from python when sending request to server which has http keepalive option turned on.

Requests send a request but in few miliseconds apache2 server is closing persistent connection by sending FIN packet which generate traceback.

I can reproduce it by following simple script.

#!/usr/bin/python3

import requests
from time import sleep

import logging
logging.basicConfig(level=logging.DEBUG)

s = requests.Session()
s.verify = False  # self-signed cert

counter = 0
txt = "test"
while True:
    counter = counter + 1
    s.post('http://localhost', data={counter:txt})
    sleep(5)

Everything is working fine, but from time to time I get following traceback. When FIN is received right after request was sent.

michalarbet at pixla:~/work$ ./request_test.py 
DEBUG:urllib3.connectionpool:Starting new HTTP connection (1): localhost:80
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
DEBUG:urllib3.connectionpool:Resetting dropped connection: localhost
DEBUG:urllib3.connectionpool:http://localhost:80 "POST / HTTP/1.1" 200 0
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 421, in _make_request
    six.raise_from(e, None)
  File "<string>", line 3, in raise_from
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 416, in _make_request
    httplib_response = conn.getresponse()
  File "/usr/lib/python3.8/http/client.py", line 1332, in getresponse
    response.begin()
  File "/usr/lib/python3.8/http/client.py", line 303, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python3.8/http/client.py", line 272, in _read_status
    raise RemoteDisconnected("Remote end closed connection without"
http.client.RemoteDisconnected: Remote end closed connection without response

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/michalarbet/.local/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
    resp = conn.urlopen(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 719, in urlopen
    retries = retries.increment(
  File "/usr/lib/python3/dist-packages/urllib3/util/retry.py", line 400, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "/usr/lib/python3/dist-packages/six.py", line 702, in reraise
    raise value.with_traceback(tb)
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 421, in _make_request
    six.raise_from(e, None)
  File "<string>", line 3, in raise_from
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 416, in _make_request
    httplib_response = conn.getresponse()
  File "/usr/lib/python3.8/http/client.py", line 1332, in getresponse
    response.begin()
  File "/usr/lib/python3.8/http/client.py", line 303, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python3.8/http/client.py", line 272, in _read_status
    raise RemoteDisconnected("Remote end closed connection without"
urllib3.exceptions.ProtocolError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./request_test.py", line 26, in <module>
    s.post('http://localhost', data={counter:txt})
  File "/home/michalarbet/.local/lib/python3.8/site-packages/requests/sessions.py", line 578, in post
    return self.request('POST', url, data=data, json=json, **kwargs)
  File "/home/michalarbet/.local/lib/python3.8/site-packages/requests/sessions.py", line 530, in request
    resp = self.send(prep, **send_kwargs)
  File "/home/michalarbet/.local/lib/python3.8/site-packages/requests/sessions.py", line 643, in send
    r = adapter.send(request, **kwargs)
  File "/home/michalarbet/.local/lib/python3.8/site-packages/requests/adapters.py", line 498, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

Apache using keepalive.
/etc/apache2/apache2.conf:KeepAliveTimeout 5
/etc/apache2/apache2.conf:MaxKeepAliveRequests 100
/etc/apache2/apache2.conf:KeepAlive On


Sending also pcap file from different reproduce test, but behaviour is same.

----------
files: mycap.pcap
messages: 374000
nosy: Michal Arbet
priority: normal
severity: normal
status: open
title: Remote end closed connection without response
versions: Python 3.8
Added file: https://bugs.python.org/file49326/mycap.pcap

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue41345>
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