code: private boolean loadingInProgress(final DruidCluster druidCluster)
    {
      for (final Object2IntMap.Entry<String> entry : targetReplicants.object2IntEntrySet()) {
        final String tier = entry.getKey();
        // if there are replicants loading in cluster
        if (druidCluster.hasTier(tier) && entry.getIntValue() > currentReplicants.getOrDefault(tier, 0)) {
          return true;
        }
      }
  
      return false;
    }
docs: Returns true if at least one tier in target replica assignment exists in cluster but does not have enough replicas.