user  nginx;
worker_processes  auto;

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

events {
    worker_connections  1024;
}

http {
    map_hash_bucket_size 128;
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    # Use a debug-oriented logging format. 
    log_format  debugging  '$remote_addr - $remote_user [$time_local] "$request" '
    '$status $body_bytes_sent '
    '"HOST: $host" "UPSTREAM: $upstream_addr" '
    '"UPSTREAM-STATUS: $upstream_status" '
    '"SSL-PROTO: $ssl_protocol" '
    '"CONNECT-HOST: $connect_host" "CONNECT-PORT: $connect_port" "CONNECT-ADDR: $connect_addr" '
    '"PROXY-HOST: $proxy_host" "UPSTREAM-REDIRECT: $upstream_http_location" "CACHE-STATUS: $upstream_cache_status" '
    '"AUTH: $http_authorization" ' ;
    
    log_format  tweaked  '$upstream_cache_status [$time_local] "$uri" '
    '$status $body_bytes_sent '
    '"HOST:$host" '
    '"PROXY-HOST:$proxy_host" "UPSTREAM:$upstream_addr" ';
    
    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 registries.
    # This is auto-generated by the entrypoint.sh based on environment variables
    map $host $dockerAuth {
        hostnames;
        include /etc/nginx/docker.auth.map;
        default "";
    }
    
    # Map to decide which hosts get directed to the caching portion.
    # This is automatically generated from the list of cached registries, plus a few fixed hosts
    # By default, we don't intercept, allowing free flow of non-registry traffic
    map $connect_host $interceptedHost {
        hostnames;
        include /etc/nginx/docker.intercept.map;
        default "$connect_host:443";
    }
    
    map $dockerAuth $finalAuth { 
        "" "$http_authorization";    # if empty, keep the original passed-in from the client
        default "Basic $dockerAuth"; # if not empty, add the Basic preamble to the auth
    }
    
    
    # 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";
    }
    
    
    # The proxy director layer, listens on 3128
    server {
        listen 3128;
        server_name _;
        
        # dont log the CONNECT proxy.
        access_log off;
        
        proxy_connect;
        proxy_connect_address $interceptedHost;
        proxy_max_temp_file_size 0;
        
        # 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

        # forward proxy for non-CONNECT request
        location / {
            return 403 "The docker caching proxy is working!";
        }
        
        location /ca.crt {
             alias /ca/ca.crt; 
        }

        # @TODO: add a dynamic root path that generates instructions for usage on docker clients
    }
    

    # The caching layer
    server {
        # Listen on both 80 and 443, for all hostnames.
        listen 80 default_server;
        listen 443 ssl default_server;
        server_name _;
        
        # Do some tweaked logging.
        access_log  /var/log/nginx/access.log  tweaked;

        # Use the generated certificates, they contain names for all the proxied registries.
        ssl_certificate /certs/fullchain.pem;
        ssl_certificate_key /certs/web.key;

        # 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 ($request_method = POST) {
            return 405 "POST method is not allowed";
        }
        if ($request_method = PUT) {
            return 405 "PUT method is not allowed";
        }
        if ($request_method = DELETE) {
            return 405  "DELETE method is not allowed";
        }
        
        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;
        
        # Add the authentication info, if the map matched the target domain.
        proxy_set_header Authorization $finalAuth;
        
        # This comes from a include file generated by the entrypoint.
        include /etc/nginx/docker.verify.ssl.conf;
        
        # Some debugging info
        # add_header X-Docker-Caching-Proxy-Real-Host $realHost;
        # add_header X-Docker-Caching-Proxy-Real-Path $realPath;
        # add_header X-Docker-Caching-Proxy-Auth $finalAuth;

        # 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 "API v1 is invalid -- you probably need auth to get a v2 endpoint working against $host -- Check the docs";
        }

        # 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;
        }
        
        # force cache of the first hit which is always /v2/ - even for 401 unauthorized.
        location = /v2/ {
            proxy_pass https://$targetHost;
            proxy_cache cache;
            proxy_cache_valid 200 301 302 307 401 60d;
        }

        # 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.caching.proxy.internal/forcecachesecure/$1/originalwas$2;
            proxy_redirect ~^http://([^:/]+)(/.+)$ http://docker.caching.proxy.internal/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;
        }

        # 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;
        }
    }
}