public Integer retrieveLatestSystemStateVersion() {
        Stat stat = new Stat();
        context.log(log, Level.FINE, "Fetching latest cluster state at '%s'", paths.latestVersion());
        final byte[] data;
        try {
            data = session.getData(paths.latestVersion(), false, stat);
        } catch (KeeperException.NoNodeException e) {
            // Initial condition: No latest version has ever been written (or ZK state completely wiped!)
            lastKnownStateVersionZNodeVersion = 0;
            maybeLogExceptionWarning(e, "No latest system state found");
            return null;
        } catch (InterruptedException | KeeperException e) {
            throw new RuntimeException("Failed to get " + paths.latestVersion(), e);
        }

        lastKnownStateVersionZNodeVersion = stat.getVersion();
        final Integer versionNumber = Integer.valueOf(new String(data, utf8));
        context.log(log, Level.INFO, "Read cluster state version %d from ZooKeeper (znode version %d)", versionNumber, stat.getVersion());
        return versionNumber;
    }
If this is called, we assume we're in shutdown situation, or we are doing it because we need a new session.
Thus we only need to free up resources, no need to notify anyone.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/ZooKeeperDatabase.java