private static String serverParameter(RoutingTable.Target target, Real real, boolean routingActive) {
        // For each real consider:
        // * if not an application-level target -> no parameters
        // * if active & routingActive = false AND the upstream contains at least one active host -> "down"
        // * if weight assigned = 0 -> "backup"
        // * if weight assigned > 0 -> "weight=<weight>"
        if (!target.applicationLevel()) return "";
        if (!(real.active() && routingActive) && target.active()) return " down";
        int weight = real.weight();
        if (weight == 0) {
            return " backup";
        } else {
            return " weight=" + weight;
        }
    }
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