Pre-Requisites
User Home Directory
A lot of what happens in hms-mirror depends on a 'user'
If your environment doesn't follow a typical home environment setup, you will NEED to set the $HOME environment variable before running the application to ensure that the application can find and store the necessary files.
Hive/TEZ Properties Whitelist Requirements
HiveServer2 has restrictions on what properties can be set by the user in a session. To ensure that hms-mirror will be able to set the properties it needs, add hive.security.authorization.sqlstd.confwhitelist.append property in the HiveServer2 Advanced Configuration Snippet (Safety Valve) for hive-site.xml with at least the following value(s) so hms-mirror can set the properties it needs:
Backups
DO NOT SKIP THIS!!!
The hms-mirror process DOES 'DROP' tables when asked. If those tables manage data like a legacy managed, ACID, or external.table.purge=true scenario, we do our best NOT to DROP those and ERROR out. But, protect yourself and make backups of the areas you'll be working in.
HDFS Snapshots
Use HDFS Snapshots to make a quick backup of directories you'll be working on. Do this, especially in the LEFT cluster. We only drop tables, so a snapshot of the database directory is good. BUT, if you are manually doing any DROP DATABASE <x> CASCADE operations, that will delete the snapshotted directory (and the snapshot). In this case, create the snapshot one level above the database directory.
Metastore Backups
Take a DB backup of your metastore and keep it in a safe place before starting.
Shared Authentication
The clusters must share a common authentication model to support cross-cluster HDFS access when HDFS is the underlying storage layer for the datasets. This means that a kerberos ticket used in the RIGHT cluster must be valid for the LEFT cluster.
For cloud storage, the two clusters must have rights to the target storage bucket.
If you can distcp between the clusters, you have the basic connectivity required to start working with hms-mirror.