void prepareRemoteSession(long sessionId) {
        // Might need to create local session first
        createLocalSessionFromDistributedApplicationPackage(sessionId);
        RemoteSession session = remoteSessionCache.get(sessionId);
        if (session == null) return;

        SessionZooKeeperClient sessionZooKeeperClient = createSessionZooKeeperClient(sessionId);
        CompletionWaiter waiter = sessionZooKeeperClient.getPrepareWaiter();
        ensureApplicationLoaded(session);
        notifyCompletion(waiter);
    }
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