private static String checkDirective(int port) {
        // nginx_http_upstream_check_module does not support health checks over https
        // a different http port is used instead, which acts as a http->https proxy for /status.html requests
        return String.format("check interval=2000 fall=5 rise=2 timeout=3000 default_down=true type=http port=%d;",
                             port);
    }
Converts a {@link RoutingTable} to Nginx's own config format.

@author Martin Polden
routing-generator/src/main/java/com/yahoo/vespa/hosted/routing/nginx/NginxConfig.java