http.response.start+body

Hi everyone.

Separated calls like the following one add a lot of latency:

    async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
        await send(
            {
                "type": "http.response.start",
                "status": self.status_code,
                "headers": self.raw_headers,
            }
        )
        await send({"type": "http.response.body", "body": self.body})

Reduce the number of calls in the chain leads to removing all useless awaits here and significantly improve performance:

    def __call__(self, scope: Scope, receive: Receive, send: Send) -> Awaitable[Any]:
        return send(
            {
                "type": "http.response.start+body",
                "status": self.status_code,
                "headers": self.raw_headers,
                "body": self.body,
            }
        )

Please pay ATTN

[andrewgodwin]

I don’t see what this is really gaining for the async case - if you want ultimate response performance, you probably shouldn’t be using ASGI in the first place. The latency it adds should be minimal with most server implementations, too, especially if you’re already handling a lot of concurrent connections.

Unless there’s a good argument to take this on other than “it’s slightly more efficient”, I will have to say no to this one.

[stas-dubrovskyi]

@andrewgodwin In a superfast app like Falcon, the difference is about 10% in RPS.