[CASSANDRA-12777] Optimize the vnode allocation for single replica per DC

• Type: Improvement
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.10
• Assignee: Dikang Gu
• Reporter: Dikang Gu

Authors

Dikang Gu

Reviewers

Branimir Lambov

• Created: 12/Oct/16 06:28
• Updated: 16/Apr/19 09:30
• Resolved: 25/Oct/16 16:00

Description

The new vnode allocation algorithm introduced in CASSANDRA-7032 is optimized for the situation that there are multiple replicas per DC.

In our production environment, most cluster only has one replica, in this case, the algorithm does not work perfectly. It always tries to split token ranges by half, so that the ownership of "min" node could go as low as ~60% compared to avg.

So for single replica case, I'm working on a new algorithm, which is based on Branimir's previous commit, to split token ranges by "some" percentage, instead of always by half. In this way, we can get a very small variation of the ownership among different nodes.