[IGNITE-22466] Sql. Support mapping to non-primary replicas

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0
• Component/s: sql
• Labels: ignite-3
• Epic Link: Read from backup
• Assignee: Konstantin Orlov
• Reporter: Konstantin Orlov
• Created: 11/Jun/24 13:51
• Updated: 04/Sep/24 16:08
• Resolved: 25/Jun/24 14:07

Description

At the moment, mapping service support mapping only on primary replicas. To improve data colocation, we may use backup replicas as well for RO queries.

Let's improve mapping service in order to take advantage of backups locality and minimize amount data sent over the network.

Some failures that should be considered during implementation:

• Replica is not ready yet
• Replica has already gone
• Replica may be too outdated (safeTime of the replica is far behind of safeTime of the primary)
• Anything else?

Issue Links

• Dependency: IGNITE-22467 PlacementDriver should have a method to return an assignments for a specified partition
• links to: PR