@Override
    public Iterator<Element> getUserItems(String name, JID senderJID) {
        List<Element> answer = new ArrayList<>();
        try {
            User user = UserManager.getInstance().getUser(name);
            RosterItem item = user.getRoster().getRosterItem(senderJID);
            // If the requesting entity is subscribed to the account's presence then
            // answer the user's "available resources"
            if (item.getSubStatus() == RosterItem.SUB_FROM ||
                    item.getSubStatus() == RosterItem.SUB_BOTH) {
                for (Session session : SessionManager.getInstance().getSessions(name)) {
                    Element element = DocumentHelper.createElement("item");
                    element.addAttribute("jid", session.getAddress().toString());
                    answer.add(element);
                }
            }
            return answer.iterator();
        }
        catch (UserNotFoundException e) {
            return answer.iterator();
        }
    }
When the local node is joining or leaving a cluster, {@link org.jivesoftware.util.cache.CacheFactory} will swap
the implementation used to instantiate caches. This causes the cache content to be 'reset': it will no longer
contain the data that's provided by the local node. This method restores data that's provided by the local node
in the cache. It is expected to be invoked right after joining ({@link #joinedCluster()} or leaving
({@link #leftCluster()} a cluster.
xmppserver/src/main/java/org/jivesoftware/openfire/disco/IQDiscoItemsHandler.java