code: @Override
      @Synchronized
      public void deregisterHost(Host host) {
          Preconditions.checkNotNull(host, "host");
          PersistentNode node = entryMap.get(host);
          Preconditions.checkNotNull(node, "Host is not present in cluster.");
          entryMap.remove(host);
          close(node);
      }
docs: Remove Host from cluster.
  
  @param host Host to be removed from cluster.