An issue was reported when a user failed to upgrade from 3.4.10 to 3.5.4 with missing snapshot file.
With this check, ZK will not load the db without a snapshot file, even the transaction log files are present and valid. This could be a problem for restoring a ZK instance which does not have a snapshot file but have a sound state (e.g. it crashes before being able to take the first snap shot with a large snapCount parameter configured).
how to use this fix
Add zookeeper.snapshot.trust.empty=true to your server configuration file and start the server.
This property will skip the check.
It is recommended to remove the property once you have a working server, because that check is important to ensure that the system is in good shape