@Override
  public synchronized MetricsMasterProcSource create(MetricsMasterWrapper masterWrapper) {
    if (masterProcSource == null) {
      masterProcSource = new MetricsMasterProcSourceImpl(masterWrapper);
    }
    return masterProcSource;
  }
Factory to create MetricsMasterProcSource when given a MetricsMasterWrapper
hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsMasterProcSourceFactoryImpl.java