protected void startCycleUpdater(long updateInterval, Runnable taskToRun) {
    if (cycleUpdaterExecutorService == null) {
      if (updateInterval > 0) {
        cycleUpdaterExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactoryBuilder()
            .setPriority(Thread.currentThread().getPriority())
            .setDaemon(true)
            .setNameFormat("Cycle-Duration-Updater-%d")
            .build());
        cycleUpdaterExecutorService.scheduleAtFixedRate(
            taskToRun,
            updateInterval, updateInterval, TimeUnit.MILLISECONDS);
      }
    }
  }
Compactor threads that runs in the metastore. It uses a {@link TxnStore}
to access the internal database.
ql/src/java/org/apache/hadoop/hive/ql/txn/compactor/MetaStoreCompactorThread.java