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Allow Channel objects to be created outside of async contexts #162

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Allow Channel objects to be created outside of async contexts #162

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8e48b44
Allow Channel objects to be created outside of async contexts
FHTMitchell Jul 21, 2022
88c0aab
use local variables to satisfy mypy
FHTMitchell Jul 22, 2022
2da4ee6
slight refactor of previous commit
FHTMitchell Jul 22, 2022
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16 changes: 10 additions & 6 deletions grpclib/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -670,7 +670,7 @@ def __init__(

self._host = host
self._port = port
self._loop = loop or asyncio.get_event_loop()
self._loop = loop
self._path = path
self._codec = codec
self._status_details_codec = status_details_codec
Expand Down Expand Up @@ -703,12 +703,13 @@ def _protocol_factory(self) -> H2Protocol:
return H2Protocol(Handler(), self._config, self._h2_config)

async def _create_connection(self) -> H2Protocol:
loop = self._loop or asyncio.get_running_loop()
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I liked your previous version of setting self._loop property here

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Hey, so I will do this, but be aware that this will mean that the following code in ipython will fail (and yes, this is absolutely something I want to do when debugging):

>>>	channel = Channel(...)
...
>>>	async with channel as ch:
...		  client = FooBase(ch)
...		  r1 = await client.bar(...)
...
>>>	async with channel as ch:
...		  client = FooBase(ch)
...		  r2 = await client.bar(...)  # this will fail because we still hold the previous loop
...

When you move to 0.5 you'll want to grab the loop explicitly at the callsite (using asyncio.get_running_loop or, even better, just use the asyncio global methods directly). This emulates doing that. By storing the loop, you're keeping a closed loop around which is not intended behaviour for asyncio.

I don't think there are any benefits in doing it the way we did it before except maybe slightly cleaner code.

Can you confirm this is what you want?

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Strange but I can't reproduce your error, even with stock grpclib with no changes.

Python 3.9.13 (main, May 24 2022, 21:28:31)
Type 'copyright', 'credits' or 'license' for more information
IPython 8.4.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from grpclib.client import Channel

In [2]: from helloworld.helloworld_pb2 import HelloRequest

In [3]: from helloworld.helloworld_grpc import GreeterStub

In [4]: channel = Channel('127.0.0.1', 50051)

In [5]: async with channel as ch:
   ...:     client = GreeterStub(ch)
   ...:     r1 = await client.SayHello(HelloRequest(name="Dr. Strange"))
   ...:

In [6]: async with channel as ch:
   ...:     client = GreeterStub(ch)
   ...:     r2 = await client.SayHello(HelloRequest(name="Dr. Strange"))
   ...:

In [7]: r1
Out[7]: message: "Hello, Dr. Strange!"

In [8]: r2
Out[8]: message: "Hello, Dr. Strange!"

Which version of IPython do you have?

BTW, as I said before you don't have to use async with to use a channel, like this:

In [4]: channel = Channel('127.0.0.1', 50051)

In [5]: greeter = GreeterStub(channel)

In [6]: await greeter.SayHello(HelloRequest(name='Dr. Strange'))
Out[6]: message: "Hello, Dr. Strange!"

In [7]: await greeter.SayHello(HelloRequest(name='Dr. Strange'))
Out[7]: message: "Hello, Dr. Strange!"

This is fine for IPython sessions or if you want to close the channel manually.

if self._path is not None:
_, protocol = await self._loop.create_unix_connection(
_, protocol = await loop.create_unix_connection(
self._protocol_factory, self._path, ssl=self._ssl,
)
else:
_, protocol = await self._loop.create_connection(
_, protocol = await loop.create_connection(
self._protocol_factory, self._host, self._port,
ssl=self._ssl,
)
Expand Down Expand Up @@ -792,11 +793,14 @@ def __del__(self) -> None:
if self._protocol is not None:
message = 'Unclosed connection: {!r}'.format(self)
warnings.warn(message, ResourceWarning)
if self._loop.is_closed():
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Placing assert self._loop is not None before using self._loop property will do the trick for mypy, this is probably the simplest way of telling to mypy that variable was initialised. If self._protocol is not None then also self._loop is not None.

try:
loop = self._loop or asyncio.get_running_loop()
except RuntimeError:
# There is no loop to handle exception on.
return
else:
if not loop.is_closed():
self.close()
self._loop.call_exception_handler({'message': message})
loop.call_exception_handler({'message': message})

async def __aenter__(self) -> 'Channel':
return self
Expand Down