@Override
    public void joinedCluster() {
        ClusterManager.getNodesInfo().forEach(nodeName -> nodeNames.put(nodeName.getNodeID(), nodeName.getHostName()));
        LOGGER.info("This node ({}/{}) has joined the cluster [seniorMember={}]", xmppServer.getNodeID(), xmppServer.getServerInfo().getHostname(), getSeniorMember());
    }
Monitors the state of the cluster, and warns admins when nodes leave or rejoin the cluster
xmppserver/src/main/java/org/jivesoftware/openfire/cluster/ClusterMonitor.java