nginx openai cache proxy (http listener, https upstream) inside docker

Using docker, I am trying to setup a local reverse proxy where :

Listen in http mode (I do not need encryption here)
Redirects requests to a https server

This is for the purpose of caching expensive requests to openai.

I am using the following configuration :

events {
    worker_connections 10;
}

http {
    proxy_cache_path /server_cache levels=1:2 keys_zone=my_cache:10m max_size=1g inactive=60m use_temp_path=off;

    server {
        listen 80;

        location /v1/chat/completions {
            proxy_pass https://api.openai.com;
            proxy_cache my_cache;
            proxy_cache_methods POST;
            proxy_cache_key "$request_method$request_uri$request_body";
            proxy_cache_valid 200 60m;
            proxy_cache_valid 404 1m;
            proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
            proxy_cache_background_update on;
            proxy_cache_lock on;
            proxy_set_header Host $host;
        }

        location / {
            proxy_pass https://api.openai.com;
            proxy_set_header Host $host;
        }
    }
}

However I get this error from the nginx logs whenever it's processing a request :

[error] 24#24: *1 SSL_do_handshake() failed (SSL: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:SSL alert number 40) while SSL handshaking to upstream

I've read I need to add some proxy_ssl_* directives and include some private keys...

But why on earth do I have to do this when the server I'm setting up is http, NOT https ? And I never need to specify any kind of cert (not to mention privates, that won't make sense) when connecting directly to the upstream https server.

Any solution ? Is it an nginx flaw ?

Solution

Some people mention adding

proxy_ssl_server_name on;

In your location block. Did you try this?

Else, if you want to proxy http to https, I've heard people usually suggest haproxy instead.