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Spawning error

See original GitHub issue

Attempting to use reload, can result in this error:

Traceback (most recent call last):
  File "example.py", line 53, in <module>
    uvicorn.run(app.__call__, reload=True)
  File "/Users/tomchristie/GitHub/encode/typesystem/venv/lib/python3.6/site-packages/uvicorn/main.py", line 255, in run
    supervisor.run(server.run, sockets=[socket])
  File "/Users/tomchristie/GitHub/encode/typesystem/venv/lib/python3.6/site-packages/uvicorn/supervisors/statreload.py", line 34, in run
    process.start()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/process.py", line 105, in start
    self._popen = self._Popen(self)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/context.py", line 284, in _Popen
    return Popen(process_obj)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/popen_spawn_posix.py", line 32, in __init__
    super().__init__(process_obj)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/popen_fork.py", line 20, in __init__
    self._launch(process_obj)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/popen_spawn_posix.py", line 47, in _launch
    reduction.dump(process_obj, fp)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
AttributeError: Can't pickle local object 'request_response.<locals>.app'

Will look into this first thing tomorrow.

Issue Analytics

State:
Created 5 years ago
Reactions:1
Comments:5 (5 by maintainers)

Top GitHub Comments

1reaction

tomchristiecommented, Mar 5, 2019

Okay. That’s a total PITA - works great in the test cases. And will work in some examples, but not others. Reason is that it turns out the way Python’s multiprocessing calls work is by serializing/deserializing the arguments to the call using pickle. Eveidently in some cases there’ll end up being something somewhere referenced by the application that’s not picklable.

You won’t see these errors running from the command line, because the application instance isn’t passed into the call - instead an import string is passed. eg example:app.

0reactions

tomchristiecommented, Mar 5, 2019

Resolved in 0.5.1