Type: New Feature
Affects Version/s: None
Fix Version/s: 0.8.x
Helix rebalancer assigns resources according to different strategies. Recently, we optimize the strategy for evenness and minimize movement. However, the evenness here only applies to partition numbers. Moreover, we've got more requests for customizable rebalancer from our users.
Take partition weight as an example:
In reality, partition replicas have different size. We use "partition weight" as an abstraction of the partition size. It can be network traffic usage, disk usage, or any other combined factors.
Given each partition may have different weights, Helix should be able to assign partition accordingly. So that the distribution would be even regarding the weight.
In this project, we are planning new rebalancer mechanism that generates resource partition assignment according to a list of "constraints". Current rebalance strategy can be regarded as one kind of constraint. Moving forward, Helix users would be able to extend the constraint interface using their own logic.
Some init discussions are in progress and we will have a proposal posted here soon.