private Method lookupSetter(Object builder, String methodName, Object ... params) throws NoSuchMethodException {
        Class<?>[] parameterTypes = new Class<?>[params.length];
        for (int i = 0; i < params.length; i++) {
            parameterTypes[i] = params[i].getClass();
        }
        Method method = builder.getClass().getDeclaredMethod(methodName, parameterTypes);
        method.setAccessible(true);
        return method;
    }
This may run on both the config server and subscribing nodes.
We only have a urlDownloader set up when client side.
config/src/main/java/com/yahoo/vespa/config/ConfigPayloadApplier.java