I'm writing a tool to test an asyncio based server end-to-end. Initially I was going to spin up the server in one terminal window, and run the test in a separate window, but then I realized that it should be possible to just do that in one script. After all, I can do it with a concurrent.futures.ThreadPoolExecutor, but I'm struggling converting the logic using await/async def.
Here's a working example using the TPE:
import argparseimport socketimport concurrent.futuresimport threadingimport socketserverclass TCPHandler(socketserver.BaseRequestHandler): def handle(self): print(f'Got data: {self.request.recv(1024).strip().decode()}')def started_server(*, server): print('starting server') server.serve_forever() print('server thread closing')def run_client(*, host, port, server): print('client started, attempting connection') with socket.create_connection((host, port), timeout=0.5) as conn: print('connected') conn.send(b'hello werld') print('closing server') server.shutdown() print('cancelled')def test_the_server(*, host, port): ex = concurrent.futures.ThreadPoolExecutor(max_workers=3) print('server a') quitter = threading.Event() server = socketserver.TCPServer((host, port), TCPHandler) a = ex.submit(started_server, server=server) b = ex.submit(run_client, host=host, port=port, server=server) print(a.result(), b.result()) print('server b')def do_it(): # Shia LeBeouf! parser = argparse.ArgumentParser(usage=__doc__) parser.add_argument("--host", default="127.0.0.1") parser.add_argument("-p", "--port", type=int, default=60025) args = parser.parse_args() exit(test_the_server(host=args.host, port=args.port))if __name__ == "__main__": do_it()How would I convert this to use an asyncio loop? I'm pretty sure that I need to spawn the server asyncio loop in a thread, but so far it's just turned out blocking, and other questions on SO have failed to provide a solution (or have been outdated).
Here's an example of something that fails for me:
import asyncioimport argparseimport socketimport concurrent.futuresimport threadingimport socketserverclass EchoHandler(asyncio.Protocol): def data_received(self, data): print(f"Got this data: {data.decode()}")async def run_server(*, server): print('starting server') server = await server async with server: print('start serving') await server.start_serving() print('waiting on close') await server.wait_closed() print('server coro closing')def started_server(*, server): print('server thread started') asyncio.run(run_server(server=server)) print('server thread finished')def run_client(*, host, port, server): print('client started, attempting connection') with socket.create_connection((host, port), timeout=0.5) as conn: print('connected') conn.send(b'hello werld') print('closing server') server.close() print('cancelled')async def fnord(reader, writer): data = await reader.read(100) message = data.decode() print('got', message)def test_the_server(*, host, port): ex = concurrent.futures.ThreadPoolExecutor(max_workers=3) print('server a') quitter = threading.Event() #server = socketserver.TCPServer((host, port), TCPHandler) server = asyncio.start_server(fnord, host, port) a = ex.submit(started_server, server=server) b = ex.submit(run_client, host=host, port=port, server=server) print(a.result(), b.result()) print('server b')def do_it(): # Shia LeBeouf! parser = argparse.ArgumentParser(usage=__doc__) parser.add_argument("--host", default="127.0.0.1") parser.add_argument("-p", "--port", type=int, default=60025) args = parser.parse_args() exit(test_the_server(host=args.host, port=args.port))if __name__ == "__main__": do_it()I was hoping that https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.Server.wait_closed would be enough that when I call server.close() on the other thread that it would shut down the server, but it doesn't appear to be the case. serve_forever behaves the same as the start_serving approach.