Allow dependency injection Config and Server

[abersheeran]

Related links:

• How do I cancel a streaming response on shutdown? #451
• Allow use custom server class #1091
• add run_server(server) convenience func #1012
• Uvicorn cannot be shutdown programmatically #742
• support @asynccontextmanager app_factory functions #1151

To solve #742 , a short and simple code:

config = Config("example:app", host="127.0.0.1", port=5000, log_level="info")
server = Server(config=config)

thread = threading.Thread(target=uvicorn.run_server, args=(server,))
thread.start()

To solve #1151

async with app_factory() as app:
    config = Config(app)
    server = Server(config=config)
    uvicorn.run_server(server)

To solve #451 and #1091

should_exit = False

class CustomServer(uvicorn.Server):
    def handle_exit(self, sig, frame):
        global should_exit
        should_exit = True
        return super().handle_exit(sig, frame)

class App:
    ...

    async def http(self, receive, send):
        """Handle http messages"""

        message = await receive()
        assert message['type'] == 'http.request'

        while message['more_body']:
            message = await receive()

        await send({
            'type': 'http.response.start',
            'status': 200,
            'headers': [
                (b'cache-control', b'no-cache'),
                (b'content-type', b'text/event-stream'),
                (b'connection', b'keep-alive')
            ]
        })

        while not should_exit:
            ............ # send some message

if __name__ == '__main__':
    config = Config(App())
    server = CustomServer(config=config)
    uvicorn.run_server(server)

[Kludex]

The examples on the description shows uvicorn.serve, but that is not available yet. We need to add from uvicorn.main import serve on the __init__.py.

[Kludex]

@euri10 Do you have something against this or can we we merge it?

[euri10]

@euri10 Do you have something against this or can we we merge it?

nothing against, that may be a breaking change though for some people, @florimondmanca will know for sure, so maybe hold it onto a minor bump if patches need to be released in between

[florimondmanca]

Well I think the general idea is quite nice.

Tho as @HansBrende pointed out, seems there’s a distinction and decision to take about whether the serve() utility should include the multiprocessing/reload code branches or not.

k don’t have much more background to tell which would best address the issues this aims at, though. Just thought I’d raise that distinction as something that should be discussed before merging.

In a all cases, one of this or #1012 should end up merged and the other one closed, right?

[florimondmanca]

I also agree with @HansBrende that the uvicorn.serve naming would be a bit confusing, as eg Server.serve() is while this is not, and this is actually calling into server.run(). I’d also be in favor of something like uvicorn.run_server() like in #1012.

[HansBrende]

Shouldn't this check go in the constructor? By the time we get here, we are already in the subprocess I believe...

[abersheeran]

I think this check should be combined with import_from_string(self.app).

[HansBrende]

Why? Isn't it preferable to "fail fast" in the main process rather than failing later in possibly N subprocesses?

[abersheeran]

When the user provides a string, checks the type in one place, but tries to import it in another far away, don't you think this is unreasonable?

If it is for this purpose, then import_from_string(self.app) should also "fail fast".

[Kludex]

Let's continue on #1012. It's easier, yep.