@Override
    public void leftCluster() {
        // The local cluster node left the cluster.
        if (XMPPServer.getInstance().isShuttingDown()) {
            // Do not put effort in restoring the correct state if we're shutting down anyway.
            return;
        }

        // Upon leaving a cluster, clustered caches are reset to their local equivalent (by the swap from the clustered
        // cache implementation to the default cache implementation that's done in the implementation of
        // org.jivesoftware.util.cache.CacheFactory.leftCluster). This means that they now hold no data (as a new cache
        // has been created). Data that's available on the local node needs to be added again.
        restoreCacheContent();

        // It does not appear to be needed to invoke any kind of event listeners for the data that was lost by leaving
        // the cluster (eg: server features provided only by other cluster nodes, now unavailable to the local cluster
        // node): the only cache that's being used in this implementation does not have an associated event listening
        // mechanism when data is added to or removed from it.
    }
Removes a feature from the information returned whenever a disco for information is
made against the server.

@param namespace the namespace of the feature to be removed.
xmppserver/src/main/java/org/jivesoftware/openfire/disco/IQDiscoInfoHandler.java