@Override
    public void shutdown()
    {
    	log.info("Flushing write cache to database");

		// node cleanup (skip when running as a cluster)
		if (!ClusterManager.isClusteringEnabled()) {
			purgeItems();
		}
    }
Purges all items from the database that exceed the defined item count on
all nodes.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/DefaultPubSubPersistenceProvider.java