public boolean loadStartTimestamps(ContentCluster cluster) {
        fleetControllerContext.log(logger, Level.FINE, () -> "Retrieving start timestamps");
        synchronized (databaseMonitor) {
            if (database == null || database.isClosed()) {
                return false;
            }
            currentlyStored.startTimestamps = database.retrieveStartTimestamps();
        }
        Map<Node, Long> startTimestamps = currentlyStored.startTimestamps;
        if (startTimestamps == null) {
            fleetControllerContext.log(logger, Level.WARNING, "Failed to retrieve start timestamps from ZooKeeper. Cluster state will be bloated with timestamps until we get them set.");
            startTimestamps = new TreeMap<>();
        }
        for (Map.Entry<Node, Long> e : startTimestamps.entrySet()) {
            cluster.setStartTimestamp(e.getKey(), e.getValue());
            fleetControllerContext.log(logger, Level.FINE, () -> "Node " + e.getKey() + " has start timestamp " + e.getValue());
        }
        return true;
    }
This is called to attempt the next task against ZooKeeper we want to try.

@return true if we did or attempted any work.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/DatabaseHandler.java