@Override
 public void registerTopicSubscriber(
     @NotNull RequestContext rc, @NotNull TopicSubscriber subscriber) {
   addToStats("topicSubscription");
   Boolean bootstrap = rc.bootstrap();
   topicSubscribers.add((TopicSubscriber<K, V>) subscriber);
   if (bootstrap != Boolean.FALSE && kvStore != null) {
     try {
       for (int i = 0; i < kvStore.segments(); i++)
         kvStore.entriesFor(i, e -> subscriber.onMessage(e.getKey(), e.getValue()));
     } catch (InvalidSubscriberException dontAdd) {
       topicSubscribers.remove(subscriber);
     }
   }
 }
 @Override
 public void unregisterTopicSubscriber(@NotNull TopicSubscriber subscriber) {
   topicSubscribers.remove(subscriber);
   removeFromStats("topicSubscription");
   subscriber.onEndOfSubscription();
 }