This is the full configuration for nginx.conf:

user www www;
worker_processes  auto;

events {
    use kqueue;
    worker_connections  1024;

http {
    include       mime.types;
    default_type  application/octet-stream;

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;

    client_max_body_size 30M;
    keepalive_timeout    10 10;

    gzip            on;
    gzip_static     on;
    gzip_vary       on;
    gzip_min_length 0;
    gzip_comp_level 9;
    gzip_buffers    16 8k;
    gzip_proxied    any;
    gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript application/json application/javascript image/svg+xml;

    charset   utf-8;
    server_tokens off;
    server_name_in_redirect off;

    proxy_buffering    on;
    proxy_cache_path   /home/cache levels=1:2 keys_zone=rubygems:256m max_size=5g inactive=24h use_temp_path=off;
    proxy_buffer_size  8k;
    proxy_buffers      8 24k;

    server {
        listen       80;
        server_name  _;

        location / {
            proxy_cache rubygems;
            proxy_cache_use_stale updating error timeout invalid_header http_500 http_502 http_503 http_504;
            proxy_cache_revalidate on;
            proxy_cache_min_uses 1;
            proxy_cache_lock on;
            proxy_cache_valid 200 301 304 2d;
            proxy_ignore_headers X-Accel-Expires Expires Cache-Control Set-Cookie;

            proxy_redirect off;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Host;
            proxy_set_header Connection "";
            proxy_http_version 1.1;

In this case Nginx is used to cache packages from