code: @Synchronized
      @SneakyThrows(Exception.class)
      private void tryInit() {
          if (!zkInit) {
              // we are making remote calls under a lock but this is only done for initialization at 
              // the start of controller process.
              ZKUtils.createPathIfNotExists(zkClient, zkPath, HostContainerMap.EMPTY.toBytes());
              hostContainerMapNode.getListenable().addListener(this::updateMap);
              hostContainerMapNode.start(true);
              updateMap();
              zkInit = true;
          }
      }
docs: Ensure required zk node is present in zookeeper.