void confirmUpload(Session session) {
        CompletionWaiter waiter = createSessionZooKeeperClient(session.getSessionId()).getUploadWaiter();
        long sessionId = session.getSessionId();
        log.log(Level.FINE, () -> "Notifying upload waiter for session " + sessionId);
        notifyCompletion(waiter);
        log.log(Level.FINE, () -> "Done notifying upload for session " + sessionId);
    }
A session for which we don't have a watcher, i.e. hitherto unknown to us.

@param sessionId session id for the new session
configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java