ZooKeeper 3.5 is trying to load an existing 3.4 data directory in which no snapshot
file is created. This usually happens if transaction count has not reached the limit of
snapshot creation. An extra startup check is introduced in 3.5.5 (ZOOKEEPER-2325) to
prevent a potential data inconsistency issue which makes ZooKeeper unable to start when
no snapshot files present. It's a completely valid scenario in 3.4, but in 3.5 it will
result in failure to start ZooKeeper.
Download the attached snapshot.0 file. For more information,
Copy it to the versioned directory. For example, version-2
within the data directory. Parameter is dataDir in your
configuration. This is the directory containing the myid file
for a peer.
Restart the peer.
Upgrade the peer. For more information, see QE-23738.