docker-registry-proxy/nginx.conf

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log debug;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

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

    # Use a debug-oriented logging format. 
    log_format  tweaked  '$remote_addr - $remote_user [$time_local] "$request" '
    '$status $body_bytes_sent '
    '"HOST: $host" "UPSTREAM: $upstream_addr" '
    '"UPSTREAM-STATUS: $upstream_status" '
    '"SSL-PROTO: $ssl_protocol" '
    '"PROXY-HOST: $proxy_host" "UPSTREAM-REDIRECT: $upstream_http_location" "CACHE-STATUS: $upstream_cache_status"';
    
    access_log  /var/log/nginx/access.log  tweaked;
    keepalive_timeout  300;
    gzip  off;

    # The cache directory. This can get huge. Better to use a Docker volume pointing here!
    # Set to 32gb which should be enough
    proxy_cache_path /docker_mirror_cache levels=1:2 max_size=32g inactive=60d keys_zone=cache:10m use_temp_path=off;
    

    # Just in case you want to rewrite some hosts. Default maps directly.
    map $host $targetHost {
        hostnames;
        default $host;
    }

    # A map to enable authentication to some specific docker hosts.
    # To use this, mount a volume in docker.
    
    map $host $dockerAuth {
        include /etc/nginx/docker.auth.*.map;
        default "";
    }
    
    # These maps parse the original Host and URI from a /forcecache redirect.
    map $request_uri $realHost {
        ~/forcecacheinsecure/([^:/]+)/originalwas(/.+) $1;
        ~/forcecachesecure/([^:/]+)/originalwas(/.+) $1;
        default "DID_NOT_MATCH_HOST";
    }

    map $request_uri $realPath {
        ~/forcecacheinsecure/([^:/]+)/originalwas(/.+) $2;
        ~/forcecachesecure/([^:/]+)/originalwas(/.+) $2;
        default "DID_NOT_MATCH_PATH";
    }

    server {
        # Listen on both 80 and 443, for all hostnames.
        listen 80 default_server;
        listen 443 ssl default_server;
        server_name _;

        # Use a fake SSL certificate. This does not matter, since the Docker clients will be configured with insecure registry
        ssl_certificate /etc/ssl/cert.pem;
        ssl_certificate_key /etc/ssl/key.pem;

        # We need to resolve the real names of our proxied servers.
        resolver 8.8.8.8 4.2.2.2 ipv6=off; # Avoid ipv6 addresses for now

        # Docker needs this. Don't ask.
        chunked_transfer_encoding on;

        # Block POST/PUT/DELETE. Don't use this proxy for pushing.
        if ($request_method = POST) {
            return 405;
        }
        if ($request_method = PUT) {
            return 405;
        }
        if ($request_method = DELETE) {
            return 405;
        }
        
        proxy_read_timeout 900;
        
        # Use cache locking, with a huge timeout, so that multiple Docker clients asking for the same blob at the same time 
        # will wait for the first to finish instead of doing multiple upstream requests.
        proxy_cache_lock on;
        proxy_cache_lock_timeout 120s;

        # Cache all 200, 301, 302, and 307 (emitted by private registries) for 60 days.
        proxy_cache_valid 200 301 302 307 60d; 
        
        # Some extra settings to maximize cache hits and efficiency
        proxy_force_ranges on;
        proxy_ignore_client_abort on;
        proxy_cache_revalidate on;

        # Hide/ignore headers from caching. S3 especially likes to send Expires headers in the past in some situations.
        proxy_hide_header      Set-Cookie;
        proxy_ignore_headers    X-Accel-Expires Expires Cache-Control Set-Cookie;
        
        # Block API v1. We dont know how to handle these.
        # Docker-client should start with v2 and fallback to v1 if something fails, for example, if authentication failed to a protected v2 resource.
        location /v1 {
            return 405;
        }

        # don't cache mutable entity /v2/<name>/manifests/<reference> (unless the reference is a digest)
        location ~ ^/v2/[^\/]+/manifests/(?![A-Fa-f0-9_+.-]+:) {
            proxy_pass https://$targetHost;
        }

        # don't cache mutable entity /v2/<name>/tags/list
        location ~ ^/v2/[^\/]+/tags/list {
            proxy_pass https://$targetHost;
        }

        # don't cache mutable entity /v2/_catalog
        location ~ ^/v2/_catalog$ {
            proxy_pass https://$targetHost;
        }

        # cache everything else
        location / {
            proxy_pass https://$targetHost;
            proxy_cache cache;

            # Handling of redirects.
            # Many registries (eg, quay.io, or k8s.gcr.io) emit a Location redirect
            # pointing to something like cloudfront, or google storage.
            # We hack into the response, extracting the host and URI parts, injecting them into a URL that points back to us
            # That gives us a chance to intercept and cache those, which are the actual multi-megabyte blobs we originally wanted to cache.
            # We to it twice, one for http and another for https.
            proxy_redirect ~^https://([^:/]+)(/.+)$ https://docker.proxy/forcecachesecure/$1/originalwas$2;
            proxy_redirect ~^http://([^:/]+)(/.+)$ http://docker.proxy/forcecacheinsecure/$1/originalwas$2;
        }

        # handling for the redirect case explained above, with https.
        # The $realHost and $realPath variables come from a map defined at the top of this file.
        location /forcecachesecure {
            proxy_pass https://$realHost$realPath;
            proxy_cache cache;
            
            # Change the cache key, so that we can cache signed S3 requests and such. Only host and path are considered.
            proxy_cache_key $proxy_host$uri;

            # Some debugging headers. Not important
            add_header X-Docker-Caching-Proxy-Real-Proto https;
            add_header X-Docker-Caching-Proxy-Real-Host $realHost;
            add_header X-Docker-Caching-Proxy-Real-Path $realPath;
        }

        # handling for the redirect case explained above, with http.
        # The $realHost and $realPath variables come from a map defined at the top of this file.
        location /forcecacheinsecure {
            proxy_pass http://$realHost$realPath;
            proxy_cache cache;
            
            # Change the cache key, so that we can cache signed S3 requests and such. Only host and path are considered.
            proxy_cache_key $proxy_host$uri;

            # Some debugging headers. Not important
            add_header X-Docker-Caching-Proxy-Real-Proto http;
            add_header X-Docker-Caching-Proxy-Real-Host $realHost;
            add_header X-Docker-Caching-Proxy-Real-Path $realPath;
        }
    }
}