public void handleMasterData(Map<Integer, Integer> data) {
            synchronized (monitor) {
                if (masterDataEvent != null && masterDataEvent.equals(data)) {
                    fleetControllerContext.log(logger, Level.FINE, () -> "New master data was the same as the last one. Not responding to it");
                } else {
                    masterDataEvent = data;
                }
                monitor.notifyAll();
            }
        }
Data store for the cluster controller.
The data is stored and distributed by ZooKeeper.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/DatabaseHandler.java