Details
Critical Description
We recently saw this: If user inadvertently starts the HBase Master after deploying new HBase binaries (any version that supports namespaces), the HMaster will start the migration to PBs the the hbase.version file per HBASE-5453 and that will write a new version file PB-serialized but with the old version number. Further restarts of the master will fail because the hbase version file has been migrated to PBs and there will be version mismatch. The right approach should be to fail safe the master if we find an old hbase.version file in order to force user to run upgrade tool.