@Override
  public CompletableFuture<List<RegionMetrics>> getRegionMetrics(ServerName serverName,
    TableName tableName) {
    Preconditions.checkNotNull(tableName,
      "tableName is null. If you don't specify a tableName, use getRegionLoads() instead");
    return getRegionMetrics(RequestConverter.buildGetRegionLoadRequest(tableName), serverName);
  }
Get the region info for the passed region name. The region name may be a full region name or
encoded region name. If the region does not found, then it'll throw an UnknownRegionException
wrapped by a {@link CompletableFuture}
@return region info, wrapped by a {@link CompletableFuture}
hbase-client/src/main/java/org/apache/hadoop/hbase/client/RawAsyncHBaseAdmin.java