@Override
  public void preFlushScannerOpen(ObserverContext<? extends RegionCoprocessorEnvironment> c,
    Store store, ScanOptions options, FlushLifeCycleTracker tracker) throws IOException {
    resetTTL(options);
  }
Internal watcher that keep "data" up to date asynchronously.
hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ZooKeeperScanPolicyObserver.java