I'd be willing to bet the opposite: CGI is more than enough for 80% of workload, performance-wise.
There are a few good reasons why CGI isn't the best today: the tooling doesn't exist, the security model is really bad, and you can cram fewer websites on a single machine, so for the same number of websites you need more machines, and that's an ecological aberration. But there is no problem about CGI being too slow.
What do you think is the upper limit of requests per second, if your HTTP server does process-per-request? For simplicity, assume server class hardware, that each request does no work besides producing a response, and an upper bound of 10k unique remote addresses (i.e. no more than 10k concurrent connections in a different model).
How do you think those metrics compare to other designs? I have an affinity for the conceptual simplicity of CGI but I've never been able to get a process-per-request server within even an order of magnitude of the performance of the more common designs. But I could be missing something!
Also, how does this design adapt to HTTP/2?
In the hundreds, which is absolutely enough for most use cases. If CGI is enough for sqlite.org displaying dynamic content (such as in https://www.sqlite.org/cgi/src/timeline), it is enough for 80% of websites. You are not bigger than sqlite.
> How do you think those metrics compare to other designs
The important question is not "is it better or worse than alternatives" but "is it enough for me". Yes, it is.
> Also, how does this design adapt to HTTP/2?
HTTP/2 doesn't change anything. Requests are on the same socket until the webserver, and the webserver forks a process for each request, multiplexes the responses and all is well.
All good! But if you're OK with O(100) RPS out of a server, then I guess basically every possible option is on the table. I bet `nc` spawning background `bash` scripts to handle requests would get to 1k RPS, even! ;)
> HTTP/2 doesn't change anything.
I guess that would work, as long as the fronting server managed all of the connection management details, stream demuxing, etc. But I wonder how you'd do that in a single thread?
It is indeed very very slow; mostly because it is not possible to pre-fork your CGI scripts (environment variables get set from the request, so each cgi program will have different values in the environment).
But, if you could pass HTTP data via some way other than environment variables, you could pre-fork the binaries and have acceptable speed[1].
[1] Pre-forking makes a large difference, and surprisingly is not too far off from other approaches to concurrent request handling. See https://unixism.net/2019/04/linux-applications-performance-i...
There's no way a CGI app can reach a million requests a second on the same hardware that a nodejs (single thread, worker loop) would take to do 1M RPS. Processes have a lot of overhead. Almost no one needs 1M RPS but it cannot be waived away that CGI is perfect for everything.
I also find the modern approach much easier to reason about and debug. I don't need Apache + fastCGI + php + php fastCGI + apache configuration to get started. I can just run `node server.js` and my web app works.
The fact that it also scales much better is a cherry on top.
You can pass environment variables to CGI scripts as well. In fact, that's exactly how CGI works. Shared resources can be cached in memory through redis, although a shared file (for example sqlite) is enough in many cases.
> I don't need Apache + fastCGI + php + php fastCGI + apache configuration to get started
I'm talking about CGI, not fastCGI
