Good point. This could be more robust. Although the reason it is "temporary" is that we are bypassing ZooKeeper connections for now if not running. As soon as we move over more of the functionality (which will be done within the M6 timeframe), we'll have to flip that switch and make ZooKeeper required. At that point, an invalid client connect string will lead to a failure when the connection is attempted. It does also support retry, though, so that can recover from failure and keep running - even if crippled - in the meantime.