private void resetTTL(ScanOptions options) {
    OptionalLong expireBefore = getExpireBefore();
    if (!expireBefore.isPresent()) {
      return;
    }
    options.setTTL(EnvironmentEdgeManager.currentTime() - expireBefore.getAsLong());
  }
Internal watcher that keep "data" up to date asynchronously.
hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ZooKeeperScanPolicyObserver.java