public static List<String> getRequestDebug(SessionContext ctx) {
        List<String> rd = (List<String>) ctx.get("requestDebug");
        if (rd == null) {
            rd = new ArrayList<String>();
            ctx.set("requestDebug", rd);
        }
        return rd;
    }
@return returns the list of request debug messages
zuul-core/src/main/java/com/netflix/zuul/context/Debug.java