@Override
  public OperationMetrics getCloseMetrics() {
    return closeMetrics;
  }
NOTE: Please refer to HBASE-9774 and HBASE-14282. Based on these two issues, HBase is moving
away from using Hadoop's metric2 to having independent HBase specific Metrics. Use
{@link BaseSourceImpl#registry} to register the new metrics.
hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSourceImpl.java