/** Debug function which checks whether the session LRU queue is in order; */
  private synchronized void verifyQueueOrder() {
    long previousTime = 0;

    Enumeration<Session> sessions = mSessionsByID.values();
    while (sessions.hasMoreElements()) {
      Session session = sessions.nextElement();

      if (session.getExpirationTime() < previousTime) {
        long sessionAge =
            (CurrentTimeUTC.getInMillis() - session.getExpirationTime()) / (60 * 60 * 1000);
        Logger.error(
            this,
            "Session LRU queue out of order! Found session which is "
                + sessionAge
                + " hour old: "
                + session);
        Logger.error(this, "Deleting all sessions...");

        mSessionsByID.clear();
        mSessionsByUserID.clear();
        return;
      }
    }
  }