====== 2022-06-04 - caching proxy in nginx ======

in one of the previous projects we had an issue on CI. TL;DR -- we needed a cache, to minimize network traffic between different locations. case was simple: there were build artifacts, stored on site A and these were needed ''N'' times on site B. since the files (once published) never changed, it was a simple matter of keeping a copy on site B, when it was 1st downloaded from site A.

after some digging it turned out that [[wp>nginx]] has a ready-to-go solution for exactly that! this is how an example configuration (''nginx.conf'') looks like:

<code>
user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 1024;
    # multi_accept on;
}


http {
    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    client_max_body_size 2048M;
    gzip off;

    server {
        listen 80 default_server;
        listen [::]:80 default_server;
        proxy_cookie_path / "/; HttpOnly; Secure";
        server_name _;
        return 301 https://$host$request_uri;
    }

    proxy_cache_path  /var/cache/nginx/ levels=1:2 keys_zone=STATIC:10m inactive=15d max_size=1800g;
    server {
        listen 443 ssl default_server;
        listen [::]:443 ssl default_server;
        proxy_cookie_path / "/; HttpOnly; Secure";
        server_name _;

        ssl_protocols TLSv1.2 TLSv1.3;
        ssl_certificate     /path/to/cert.pem;
        ssl_certificate_key /path/to/key.pem;

        location / {
            proxy_pass             https://actual.server.to.offload;
            proxy_cache_methods    GET HEAD;
            proxy_set_header       Host $host;
            proxy_buffering        on;
            proxy_cache            STATIC;
            proxy_cache_valid      200  10d;
            proxy_cache_use_stale  error timeout invalid_header updating
                                   http_500 http_502 http_503 http_504;
        }
    }
}
</code>

this coveres: caching, cache lifetime management, HTTPS and HTTP to HTTPS redirection. all in 49 lines of config, including formatting. :D once deployed, there were no further issues observed. XXI century magic! ;)