@SuppressWarnings("unchecked")
    public static synchronized void joinedCluster() {
        cacheFactoryStrategy = clusteredCacheFactoryStrategy;
        // Loop through local caches and switch them to clustered cache (purge content)
        Arrays.stream(getAllCaches())
            .filter(CacheFactory::isClusterableCache)
            .forEach(cache -> {
                final CacheWrapper cacheWrapper = ((CacheWrapper) cache);
                Cache clusteredCache = cacheFactoryStrategy.createCache(cacheWrapper.getName());
                if (cacheWrapper.getWrappedCache() instanceof SerializingCache) {
                    final SerializingCache serializingCache = (SerializingCache) cacheWrapper.getWrappedCache();
                    clusteredCache = new SerializingCache(clusteredCache);
                    ((SerializingCache) clusteredCache).registerClasses(serializingCache.getKeyClass(), serializingCache.getValueClass());
                }
                cacheWrapper.setWrappedCache(clusteredCache);
            });
        clusteringStarting = false;
        clusteringStarted = true;
        log.info("Clustering started; cache migration complete");
    }
Notification message indicating that this JVM has joined a cluster.
xmppserver/src/main/java/org/jivesoftware/util/cache/CacheFactory.java