@Override
  public CompletableFuture<ServerName> getActiveMaster() {
    return tracedFuture(
      () -> this
        .<GetActiveMasterResponse> call(
          (c, s, d) -> s.getActiveMaster(c, GetActiveMasterRequest.getDefaultInstance(), d),
          GetActiveMasterResponse::hasServerName, "getActiveMaster()")
        .thenApply(resp -> ProtobufUtil.toServerName(resp.getServerName())),
      getClass().getSimpleName() + ".getActiveMaster");
  }
Simple helper to transform the result of getMetaRegionLocations() rpc.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AbstractRpcBasedConnectionRegistry.java