@Override
    public void shutdown()
    {
        // OF-2086: Persist cached pubsub data prior to shutdown
        flushPendingChanges( false );
        TaskEngine.getInstance().cancelScheduledTask( flushTask );
        delegate.shutdown();
    }
Cache for recently accessed published items.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/CachingPubsubPersistenceProvider.java