[IGNITE-22067] Make lease distribution more even

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Labels: ignite-3
• Assignee: Unassigned
• Reporter: Denis Chudov
• Created: 18/Apr/24 09:50
• Updated: 19/Apr/24 17:33

Description

Motivation

Currently, if we have a cluster of 3 nodes and a zone of 5 partitions, there is relatively high chance that some node will have no primary replica for any partition located on it.

For 10 partition this chance is much lower but still exists.

It shows that LeaseUpdater#nextLeaseHolder provides distribution far from even.

Definition of done

Initial lease distribution has to be made decently even. However, it can be not preserved during the lifetime of the cluster, because leases don't have to be moved every time when the topology changes.

Implementation notes

We can make the distribution based on node priority. Nodes having less leases on them will have higher priority. Later this approach can be modified in order to calculate the node priority using user load, hot data metrics, etc. This will help us with IGNITE-18879 as well.

Issue Links

• is related to: IGNITE-18879 Leaseholder candidates balancing