enable READ_WRITE support for federated metastores

[rpoluri]

As a user of WD I like to run DDL on federated metastores So that I can run ETL againt primary metastore and update federated central datalake.

Acceptance Criteria: ability to configure access-control-type option for federated metastores with atleast following possible values READ_ONLY, READ_WRITE.

[teabot]

Some additional information. There are a number of write operations in the metastore whose requests do not contain database/table name context, and so cannot be routed to federated instances. We believe that this is not an issue for general operation, but may be a problem if you are wanting to use certain specific Hive features. At this time we believe the following could not be supported in a writable federation model:

• Create database: could perhaps use the prefix if that mode is enabled?
• Function handling: create/delete/get functions
• Type handling: create/delete/get types (although I can't see how these are surfaced in Hive)
• Keys foreign/primary
• Locks
• Transactions / compact
• Security management: roles, prinicpals, grant/revoke
• Delegation tokens (Kerberos?)
• Notifications
• Config management
• File metadata / cache

[patduin]

You can add create database to that list

[rpoluri]

Thanks for the info, our current use-case is limited to managing tables and partitions through waggle-dance federation, so should be fine with above limitations.

I also think anything that is not specific to schema should be managed by datalake owner.