Requests library can hang indefinitely on windows, even if a timeout is set

[earonesty]

Summary.

Assume you have a website that listens for and accepts connections, but never responds.

requests.get('https://sitethatneverresponds.com', timeout=1)

I expect this should always raise a timeout error.

Instead, if you put Windows into "sleep" mode during an openssl handshake, then wake it up a few minute later, socket events are silently dropped and the socket hangs forever.

Reproduction Steps

On a laptop run do this a bunch of times:

requests.get('https://sitethatneverresponds.com', timeout=1)

Then close the laptop lid, and lift it up 5 minutes later (or whatever the tcp discard window is). The get request never times out, and never returns. If someone knows a better way of making a socket "disappear" and not time out, let me know.

It's possible to get a call stack by turning on python's tracing system and killing the process:

Call stack of hung thread:

Thread 0x000070000823a000 (most recent call first):
  File "site-packages/OpenSSL/SSL.py", line 1813 in recv_into
  File "site-packages/urllib3/contrib/pyopenssl.py", line 313 in recv_into
  File "socket.py", line 586 in readinto
  File "http/client.py", line 258 in _read_status
  File "http/client.py", line 297 in begin
  File "http/client.py", line 1331 in getresponse
  File "site-packages/urllib3/connectionpool.py", line 421 in _make_request
  File "site-packages/urllib3/connectionpool.py", line 677 in urlopen
  File "site-packages/requests/adapters.py", line 449 in send
  File "site-packages/requests/sessions.py", line 643 in send

Related Issue with pyopenssl:

pyopnessl, by not doing it themselves, has essentially decided that the caller must handle this by putting the socket into non-blocking mode, and calling select in a loop:

See: pyca/pyopenssl#168 for potential solutions.

System Information

$ python -m requests.help

{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": "2.8"
  },
  "idna": {
    "version": "2.9"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.6.8"
  },
  "platform": {
    "release": "10",
    "system": "Windows"
  },
  "pyOpenSSL": {
    "openssl_version": "1010104f",
    "version": "19.1.0"
  },
  "requests": {
    "version": "2.23.0"
  },
  "system_ssl": {
    "version": "1000211f"
  },
  "urllib3": {
    "version": "1.25.8"
  },
  "using_pyopenssl": true

[earonesty]

I'm going to write a program that makes this easy to reproduce, then reopen if I can figure it out.

[sigmavirus24]

@earonesty I belive you're confused about what functionality timeout provides in requests. Please search open and closed issues and read those, or read the docs