Hey. Google Keystone tech lead here. We are aware of the issue, and we've stopped the release. We're building a replacement that fixes the problem. In the meantime, to fix affected machines:
Because in larger clusters, the cluster can fix any issues if one hosts goes offline (load balancing) or a database gets corrupted.
In a single cluster configuration, anything going wrong can destroy your cluster's capability. Think of it as RAID, the more drives, the more you can do for high availability.
The version of Keystone packaged with Chrome is not affected by this bug, so allowing it to reinstall Keystone will not recreate the issue.