@Override
  public CompletableFuture<String> getClusterId() {
    return tracedFuture(
      () -> this
        .<GetClusterIdResponse> call(
          (c, s, d) -> s.getClusterId(c, GetClusterIdRequest.getDefaultInstance(), d),
          GetClusterIdResponse::hasClusterId, "getClusterId()")
        .thenApply(GetClusterIdResponse::getClusterId),
      getClass().getSimpleName() + ".getClusterId");
  }
Simple helper to transform the result of getMetaRegionLocations() rpc.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AbstractRpcBasedConnectionRegistry.java