Python 3.7 "TCP echo server using streams" sample code does not work with uvloop. #221

dstruck · 2019-01-28T10:56:05Z

uvloop version: 0.12.0
Python version: 3.7.1
Platform: Linux
Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: not tested

Running the following code (source: https://docs.python.org/3/library/asyncio-stream.html#tcp-echo-server-using-streams) with uvloop:

import asyncio
import uvloop
import sys

async def handle_echo(reader, writer):
  data = await reader.read(100)
  message = data.decode()
  addr = writer.get_extra_info('peername')

  print(f"Received {message!r} from {addr!r}")

  print(f"Send: {message!r}")
  writer.write(data)
  await writer.drain()

  print("Close the connection")
  writer.close()

async def main():
  server = await asyncio.start_server(handle_echo, '127.0.0.1', 8888)

  addr = server.sockets[0].getsockname()
  print(f'Serving on {addr}')

  async with server:
    await server.serve_forever()

uvloop.install()

print("python version:", sys.version)
print("uvloop version:", uvloop.__version__)

asyncio.run(main())

Produces the following error message:

python uvlopp_issue.py 
python version: 3.7.1 (default, Dec 14 2018, 19:28:38) 
[GCC 7.3.0]
uvloop version: 0.12.0
Serving on ('127.0.0.1', 8888)
Traceback (most recent call last):
  File "uvlopp_issue.py", line 36, in <module>
    asyncio.run(main())
  File "/home/test/miniconda3/lib/python3.7/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "uvloop/loop.pyx", line 1451, in uvloop.loop.Loop.run_until_complete
  File "uvlopp_issue.py", line 27, in main
    async with server:
AttributeError: __aexit__

1st1 · 2019-01-30T01:01:51Z

Thank you for reporting. This is basically a duplicate of #211.

jlaine · 2019-02-16T19:58:03Z

This was fixed by PR #224

ahesford · 2019-03-11T00:50:17Z

I don't believe PR #224 fixes this issue. This issue is caused because the stock asyncio.base_events.Server in Python 3.7 was made into an asynchronous context manager. The entry method is simple:

async def __aenter__(self):
    return self

while the exit method closes the server:

async def __aexit__(self, *exc):
    self.close()
    await self.wait_closed()

The TCP echo server uses this manager in an async with server clause to ensure the server closes.

The uvloop replacement, uvloop.loop.Server, does not implement the methods for an asynchronous context manager in the master branch or in commit #8fac545a9351935eefc0c8d281bebd0dd2917d66 to address PR #224.


        Make Server an asynchronous context manager (fixes: MagicStack#221)

The Server class was missing __aenter__ and __aexit__ magic methods to allow usage of the form: async with server: await server.serve_forever()


        Make Server an asynchronous context manager (fixes: MagicStack#221)

The Server class was missing __aenter__ and __aexit__ magic methods to allow usage of the form: async with server: await server.serve_forever()


        Make Server an asynchronous context manager (fixes: MagicStack#221)

The Server class was missing __aenter__ and __aexit__ magic methods to allow usage of the form: async with server: await server.serve_forever()

cemsbr · 2019-06-21T15:16:46Z

The error persists. Won't the fix be merged?

Edit: more info:

uvloop 0.12.2
Python 3.7.3
Platform: Linux

jlaine · 2019-06-22T20:31:09Z

The fix landed for v0.13.0, you can for instance give the release candidate a go: https://github.com/MagicStack/uvloop/releases/tag/v0.13.0rc1

1st1 added the missing feature label Jan 30, 2019

jlaine closed this Feb 16, 2019

jlaine reopened this Mar 11, 2019

1st1 closed this in d6c67e7 Mar 17, 2019

MagicStack / uvloop

Python 3.7 "TCP echo server using streams" sample code does not work with uvloop. #221

Python 3.7 "TCP echo server using streams" sample code does not work with uvloop. #221

dstruck commented Jan 28, 2019 •

edited

1st1 commented Jan 30, 2019

jlaine commented Feb 16, 2019

ahesford commented Mar 11, 2019

cemsbr commented Jun 21, 2019 •

edited

jlaine commented Jun 22, 2019

MagicStack / uvloop

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Python 3.7 "TCP echo server using streams" sample code does not work with uvloop. #221

Python 3.7 "TCP echo server using streams" sample code does not work with uvloop. #221

Comments

dstruck commented Jan 28, 2019 • edited

1st1 commented Jan 30, 2019

jlaine commented Feb 16, 2019

ahesford commented Mar 11, 2019

cemsbr commented Jun 21, 2019 • edited

jlaine commented Jun 22, 2019

dstruck commented Jan 28, 2019 •

edited

cemsbr commented Jun 21, 2019 •

edited