Preparing ZooKeeper for upgrade

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.

Solution is:

  1. Download the attached snapshot.0 file. For more information, see ZOOKEEPER-3056.
  2. 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.
  3. Restart the peer.
  4. Upgrade the peer. For more information, see QE-23738.