Provide access to response TcpStream

[YuzhongHuangCS]

• I have looked for existing issues (including closed) about this

Feature Request

Motivation

I am trying to use sendfile syscall to serve static file (tower issue link), which require access to response TcpStream.

Proposal

Currently, axum require request handler to return an object implement IntoResponse, and the framework will write it to response TcpStream.

I wish the axum could provide a way to access response TcpStream in request handler.

Alternatives

Use the current 2 copy implementation.

[davidpdrsn]

Thats not compatible with axum being based on tower. tower::Service is pretty strictly async fn(Request) -> Response. Any other optimization would require that you interact with hyper, not axum.

[programatik29]

This issue isn't related to axum.

You can try to control underlying stream by using a wrapper stream. Here is an example to do request header read timeouts. With more effort you can write custom stuff using same principle. You might get into fight with underlying hyper implementation about who is writing stuff so be careful.

[jplatte]

Let's continue discussion on the tower-http issue, since axum clearly has nothing to do with the feature request.