I'm not sure I follow - you want a smart, small webserver that takes in a http request and updates an analytic store based on headers?

Sounds like something nginx might handle via lua scripting?

Otherwise, maybe you want: https://github.com/lammertb/libhttp

Or you might want to look at either of:

https://www.acme.com/software/thttpd/

https://github.com/openbsd/src/tree/master/usr.sbin/httpd

If you really want to build (another) web server in C.

Not entirely clear why want to use C for this, though?

for some applications it really might be easier to write a little thing than integrate into some giant framework. and I do think that building these things really helps one understand what's going on in all those layers

but I have to agree about C. unless the whole point is to ingrate with some existing codebase, there are several language choices which should turn this from a day or two of work to an hour or two - with a more robust outcome

I want to consume HTTP headers at the lowest possible level. The webserver would output a custom log file for direct consumption.

There are certainly off the shelf options, but I enjoy reinventing the wheel and dislike dependencies. I'd like to use C because I have interest in OS level webservers.

I would probably go for rust over c if the only reason for c is "os level". But either way, this is for requests from "real" http clients, eg: web browsers? Presumably you're already "trapped" at a pretty high level, like tls, http/2 etc?

Otoh, if low level is what you want, maybe look at:

https://2ton.com.au/rwasa/

and/or the library it is built on.

On the other hand, if you just want to log headers to a file, caddy can do that in a few lines:

https://caddyserver.com/docs/caddyfile/directives/log

AFAIK it can't log request bodies out of the box (like the content of a POST).

this is a 500 line server running in kernel mode on nanos

https://github.com/nanovms/nanos/blob/master/src/http/http.c

In that case you might be better off looking at writing a plugin for your existing webserver.

nginx, apache, etc, all allow writing modules that can be invoked at various parts of the HTTP-communication.

I don't technically run a webserver. I've built around Azure App Services which runs gunicorn behind the scenes.

Also, I rather own the majority of my stack even though its slower, harder, and more problematic.

Parse server logs, if that helps.