@Override
  public int hashCode() {
    return new HashCodeBuilder(17, 31)
        .append(nameserviceId)
        .append(clusterId)
        .append(blockPoolId)
        .toHashCode();
  }
@Test
  public void testHashCode() {
    Set<FederationNamespaceInfo> set = new TreeSet<>();
    // set an empty bpId first
    set.add(new FederationNamespaceInfo("", "nn1", "ns1"));
    set.add(new FederationNamespaceInfo("bp1", "nn2", "ns1"));
    assertThat(set).hasSize(2);
  }