@Override
  public void start() {
    ThreadFactory threadFactory = new ThreadFactoryBuilder()
      .setNameFormat("DatabaseMetricsSource-%d")
      .build();
    executor = Executors.newSingleThreadExecutor(threadFactory);
    LOG.info("Started Ambari DB Metrics source...");
  }
Initialize filter sets (Entities and keywords) to know which metrics to track vs drop.
ambari-server/src/main/java/org/apache/ambari/server/metrics/system/impl/DatabaseMetricsSource.java