Minimal example of an "ASGI-like" streaming server with Twisted

README.md

To execute this example:

• in a terminal, run:

python async_stream_server.py

• in another terminal, run:

curl http://localhost:1234/

async_stream_server.py

import asyncio
from twisted.internet import asyncioreactor

twisted_loop = asyncio.new_event_loop()
asyncioreactor.install(twisted_loop)

import time
from sys import stdout

from twisted.web import http
from twisted.python.log import startLogging
from twisted.internet import reactor, endpoints

CHUNK_SIZE = 2**16


def async_partial(async_fn, *partial_args):
    async def wrapped(*args):
        return await async_fn(*partial_args, *args)
    return wrapped


def iterable_content():
    for _ in range(5):
        time.sleep(1)
        yield b"a" * CHUNK_SIZE


async def application(send):
    for part in iterable_content():
        await send(
            {
                "body": part,
                "more_body": True,
            }
        )
    await send({"more_body": False})


class Dummy(http.Request):
    def process(self):
        asyncio.ensure_future(
            application(send=async_partial(self.handle_reply)),
            loop=asyncio.get_event_loop()
        )

    async def handle_reply(self, message):
        http.Request.write(self, message.get("body", b""))
        if not message.get("more_body", False):
            http.Request.finish(self)
        print('HTTP response chunk')


class DummyFactory(http.HTTPFactory):
    def buildProtocol(self, addr):
        protocol = http.HTTPFactory.buildProtocol(self, addr)
        protocol.requestFactory = Dummy
        return protocol


startLogging(stdout)
endpoints.serverFromString(reactor, "tcp:1234").listen(DummyFactory())
asyncio.set_event_loop(reactor._asyncioEventloop)
reactor.run()