@Override
  public long getExpirationTime() throws EntryNotFoundException {
    // if this is an invalidate action and region has already been invalidated,
    // then don't expire again until the full timeout from now.
    ExpirationAction action = getAction();
    if (action == ExpirationAction.INVALIDATE || action == ExpirationAction.LOCAL_INVALIDATE) {
      if (getLocalRegion().isRegionInvalid()) {
        int timeout = getTTLAttributes().getTimeout();
        if (timeout == 0) {
          return 0L;
        }
        timeout = (int) normalizeToMillis(timeout);
        // Sometimes region expiration depends on lastModifiedTime which in turn
        // depends on entry modification time. To make it consistent always use
        // cache time here.
        return timeout + getLocalRegion().cacheTimeMillis();
      }
    }
    // otherwise, expire at timeout plus last modified time
    return getTTLExpirationTime();
  }
@return the absolute time (ms since Jan 1, 1970) at which this region expires, due to either
        time-to-live or idle-timeout (whichever will occur first), or 0 if neither are used.
geode-core/src/main/java/org/apache/geode/internal/cache/RegionTTLExpiryTask.java