Python bi-directional streaming holding the connection?

[Clint Olsen]

I have a use case where the client needs to send some status updates to the server, but I also need the server to be able to notify the client if the server shuts down for any reason. My thought was bi-directional streaming makes the most sense.

The difference in my case is that I don't need to set up multiple RPC calls for this. I could theoretically hold a channel open a channel and send multiple messages fed via a queue.

Consider this abomination:

---- snip ----

import asyncio
import grpc
import bidirectional_pb2_grpc
import bidirectional_pb2


sendq = asyncio.Queue()
recvq = asyncio.Queue()

def make_message(message):
    return bidirectional_pb2.Message(
        message=message
    )

async def generate_messages():
    print('Generating')
    while True:
        message = await sendq.get()
        msg = make_message(message)
        print(f'Sending {msg.message}')
        yield msg
        await asyncio.sleep(3600)


async def connect(stub):
    responses = stub.GetServerResponse(generate_messages())
    while True:
        async for response in responses:
            recvq.put_nowait(response.message)


async def run():
    async with grpc.aio.insecure_channel('localhost:50051') as channel:
        stub = bidirectional_pb2_grpc.BidirectionalStub(channel)
        asyncio.create_task(connect(stub))
        sendq.put_nowait('First message')
        sendq.put_nowait('Second message')
        sendq.put_nowait('Third message')
        sendq.put_nowait('Fourth message')
        sendq.put_nowait('Fifth message')

        print('Waiting for receive')

        while True:
            mesg = await recvq.get()
            print(f'Received {mesg}')

if __name__ == '__main__':
    asyncio.get_event_loop().run_until_complete(run())

---- snip ----

I wasn't sure what the default timeouts are for grpc are so I added 1 hour delays between each transmission. Things seemed to work OK, but is this ill advised? I haven't seen any examples of anything like this out in the wild.

Thanks,

-Clint