Is the idea to provide asynchronous / async-friendly APIs on the stub,
service, or both? Based on my experience, I think designing an asynchronous
api for rpc services is probably trickier, particularly for streaming
replies. The simple and developer-user friendly generator idiom for
streaming replies doesn't translate to asyncio coroutines, which can only
return once. Coroutine generators are not implemented in python 3.5, see
https://www.python.org/dev/peps/pep-0492/#coroutine-generators
What I think this means is that an asynchronous rpc method with a streaming
reply would have to push elements onto a queue or other object representing
a stream, rather than returning them directly. Something like the following:
async def MethodWithStreamingReplies(request, reply_stream):
while some_condition:
item = await some_coroutine()
reply_stream.push(item)
reply_stream.close()
Note that the reply stream needed to be closed explicitly; unlike a
generator which raises StopIteration once it is exhausted, the reply stream
presumably needs a terminating sentinel to notify its consumer that it has
been exhausted.
On Monday, 12 September 2016 12:47:21 UTC-4, Nathaniel Manista wrote:
>
> There's been a <https://github.com/grpc/grpc/issues/4629> great
> <https://github.com/grpc/grpc/issues/6046> deal
> <https://github.com/grpc/grpc/issues/7910> of
> <https://groups.google.com/d/msg/grpc-io/OyREQk-TnbI/drBlO6hQCgAJ>
> interest
> <https://groups.google.com/forum/#!searchin/grpc-io/python%7Csort:relevance/grpc-io/17Cd5lgtuhw/tR5dJ8hgCgAJ>
>
> in enhancing gRPC Python to work with asynchronous frameworks and language
> features. While gRPC has been open source for some time we haven't until
> now done much in the way of community-driven development; asynchronous gRPC
> Python is a chance to try out a more direct open process. Please
> participate!
>
> For those of you that have found workarounds
> <https://github.com/grpc/grpc/issues/4629#issuecomment-244944914> and drafted
> patches <https://github.com/grpc/grpc/issues/7910#issuecomment-243290904>:
> you probably know more about the work ahead than I do, and I'd especially
> appreciate your involvement.
>
> Process-wise, I have drafted this initial document
> <https://github.com/grpc/grpc-experiments/blob/master/python/async/README.md>,
>
> and for at least initial design I'd like to proceed by pull requests
> fleshing out the document with proposals and plans. Pull requests to gRPC
> itself will also of course be part of the conversation - please remember to
> include test coverage not only for code health's sake but also as an
> illustration of new behavior.
>
> Looking forward,
> -Nathaniel
>
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