Deserializing pickled starlette.applications.Starlette object fails with RecursionError: maximum recursion depth exceeded

[edoakes]

Starlette apps are not currently pickleable:

>>> from starlette.applications import Starlette
>>> app = Starlette()
>>> import pickle
>>> pickle.loads(pickle.dumps(app))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/eoakes/miniforge3/envs/ray/lib/python3.8/site-packages/starlette/datastructures.py", line 702, in __getattr__
    return self._state[key]
  File "/Users/eoakes/miniforge3/envs/ray/lib/python3.8/site-packages/starlette/datastructures.py", line 702, in __getattr__
    return self._state[key]
  File "/Users/eoakes/miniforge3/envs/ray/lib/python3.8/site-packages/starlette/datastructures.py", line 702, in __getattr__
    return self._state[key]
  [Previous line repeated 995 more times]
RecursionError: maximum recursion depth exceeded

This is due to starlette.datastructures.State overriding __getattr__ without providing a __reduce__ method.

Adding the following method to State fixes the issue:

    def __reduce__(self):
        return State, (self._state,)

Would be happy to submit a patch to fix this.

[muazhari]

Any updates? Getting the same error when using dill & multiprocessing manager queue with the starlette app (fastapi) as elements.

RemoteError: 
---------------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python3.10/multiprocessing/managers.py", line 253, in serve_client
    request = recv()
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 251, in recv
    return _ForkingPickler.loads(buf.getbuffer())
  File "/usr/local/lib/python3.10/dist-packages/dill/_dill.py", line 303, in loads
    return load(file, ignore, **kwds)
  File "/usr/local/lib/python3.10/dist-packages/dill/_dill.py", line 289, in load
    return Unpickler(file, ignore=ignore, **kwds).load()
  File "/usr/local/lib/python3.10/dist-packages/dill/_dill.py", line 444, in load
    obj = StockUnpickler.load(self)
  File "/usr/local/lib/python3.10/dist-packages/starlette/datastructures.py", line 699, in __getattr__
    return self._state[key]
  File "/usr/local/lib/python3.10/dist-packages/starlette/datastructures.py", line 699, in __getattr__
    return self._state[key]
  File "/usr/local/lib/python3.10/dist-packages/starlette/datastructures.py", line 699, in __getattr__
    return self._state[key]
  [Previous line repeated 2984 more times]
RecursionError: maximum recursion depth exceeded
---------------------------------------------------------------------------