Eio support

[madroach]

Are there plans to implement conduit-eio ?

[ajbt200128]

Would be great to have EIO support from conduit with 5.2 released

[talex5]

It might be good to rethink the design a bit before doing that. I'm always a bit confused by conduit, but it seems to provide three separate features:

• An abstraction for byte streams (e.g. Conduit_lwt_unix.flow is a TCP socket, a Unix-domain socket, or a vchan).
• Common APIs for tls and ssl, depending on what is installed.
• A way to resolve endpoints into connections (with a fixed set of supported endpoint types).

Eio provides the Eio.Flow abstraction for byte streams, so possibly the first isn't needed.

In #420 (comment), @avsm said:

I'm tempted to suggest dropping support for the OpenSSL in Conduit

I'm not sure what uses the resolver. I'm also not sure how it works as e.g. the TLS endp variant doesn't contain any configuration settings (e.g. certificates and keys).

Perhaps we should start by making a list of features people want. Some things I'm interested in are:

1. Adding TLS support to cohttp-eio without having to care about tls vs ssl.
2. Having a common command-line syntax for saying where a service should listen (e.g. tcp:8080 or unix:/run/socket).