Set tcp nodelay on sockets

[liss-h]

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

Feature Request

Motivation

Currently axum does not set tcp-nodelay on accepted connections.
As demonstrated in this issue: hyperium/hyper#3269 this default behaviour can heavily degrade performance in some use cases.

Proposal

Add some way to set TCP_NODELAY on the accepted connections (via TcpStream::set_nodelay).

Variants

1. Make it the default behaviour for axum::serve by just setting it on each accepted connection
2. Add a function to axum::serve::Serve<> (like graceful_shutdown) of which the usage could look something like this:

axum::serve(...).set_nodelay(true).await

Some Notes/Questions

As far as I understood you want to keep this part of axum relatively simple and prefer to refer to hyper-util for more complex tasks. However, this would be a relatively small change (I can create a PR if you want) so it doesn't add much code complexity and can give huge performance boosts.

So I guess questions:

1. Do you want this at all?
2. If you do: What would you like for an interface?

[nylonicious]

#2479 is going to let you set settings for the accepted connections before handing them over. However it's a breaking change so unfortunately you will need to wait for 0.8.

[x1957]

I've also encountered this issue, it's very important！thanks

[jplatte]

A PR for a tcp_nodelay method on Serve would be appreciated. Then for 0.8 we can see if it makes sense to remove again because of #2479.