private static String methodCacheKey(Object builder, String methodName, Object[] params) {
        StringBuilder sb = new StringBuilder();
        sb.append(builder.getClass().getName())
          .append(".")
          .append(methodName);
        for (Object param : params) {
            sb.append(".").append(param.getClass().getName());
        }
        return sb.toString();
    }
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