@Override
  public ScheduledExecutorService getExecutor() {
    return ExecutorSingleton.INSTANCE.scheduler;
  }
Class to handle the ScheduledExecutorService{@link ScheduledExecutorService} used by
MetricsRegionAggregateSourceImpl, and JmxCacheBuster
hbase-hadoop-compat/src/main/java/org/apache/hadoop/metrics2/lib/MetricsExecutorImpl.java