nginx config for resolving docker containers

add_docker_inspect_to_www-data.sh

echo "www-data ALL=(ALL:ALL) NOPASSWD:/usr/bin/docker inspect *" >> /etc/sudoers

add_lua_shared_dict.sh

sed -i "s/http {/http {\n        lua_shared_dict upstream_cache 1m;/" /etc/nginx/nginx.conf

nginx-proxy.conf

server {
    listen *;
    server_name {{host}};
    gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;

    set $attempt 0;
    
    location / {
        try_files '/dev/null' @run;
    }

    location @run {
        internal;
        set $container_name "{{container_name}}";
        set $upstream "";
        
        rewrite_by_lua '
             local attempt = tonumber(ngx.var.attempt)
        
             if attempt > 1 then
                ngx.log(ngx.ALERT, "Upstream down")
                ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
             end
        
             local routes = ngx.shared.upstream_cache
             
             if attempt > 0 then
                ngx.log(ngx.ALERT, "Deleteing cache")
                routes:delete(ngx.var.http_host)
             end
             
             ngx.var.attempt = attempt + 1

             -- try cached route first
             local route = routes:get(ngx.var.http_host)
             if route == nil then
                 ngx.log(ngx.ALERT, "Asking docker about IP of " .. ngx.var.http_host)
                 local handle = io.popen("sudo /usr/bin/docker inspect --format \'{{ .NetworkSettings.IPAddress }}\' " .. ngx.var.container_name)
                 local result = handle:read("*a")
                 handle:close()
                 
                 if (result == nil or result == "") then
                     routes:delete(ngx.var.http_host)
                     ngx.log(ngx.ALERT, "Got empty IP, exiting")
                     ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
                 else
                    ngx.log(ngx.ALERT, "Got IP " .. result)
                    route = result
                 end
             end
              
             if route ~= nil then
                 ngx.var.upstream = route:gsub("^%s*(.-)%s*$", "%1")
                 routes:set(ngx.var.http_host, route)
             else
                 ngx.exit(ngx.HTTP_NOT_FOUND)
             end
        ';
        
        error_page 504 = @run;
        
        proxy_buffering             off;
        proxy_set_header            Host $host;
        proxy_set_header            X-Real-IP  $remote_addr;
        proxy_set_header            X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_redirect              off;
        proxy_send_timeout          30;
        proxy_read_timeout          30;
        proxy_connect_timeout       2;
        
        proxy_pass $scheme://$upstream;
        
    }

}