I wish it were a bit more robust than it is. The ZooKeeper version we run (3.3.4, admittedly not the newest) reports the wrong version number (3.3.3) and has a major bug in the way it does snapshots. We found that it doesn't serialize the tree of nodes to disk correctly so there is a race condition where it writes a node even though the parent of that node has been deleted. Then ZK tries to reload from the flawed snapshot but it cannot so it crashes which results in endless leader elections that never resolve..

All software has bugs and these specific problems have been fixed in newer versions, but they are super scary issues to run into with your distributed coordination service.