Apply minIndexReplicas on config change

[akryvko]

Apply minIndexReplicas on config change

[mikkeloscar]

@akryvko thanks for clarifying. I realized that we only do es node scaling without looking at CPU metrics, but we don't do any index scaling without considering the CPU metrics, even when the config has changed.

I would consider this a bug (probably we didn't implement it as it wasn't needed in the past).

[mikkeloscar]

Right now you should be able to "enable" autoscaling and just set min and max settings to the same value such that it can't autoscale. It's a bit of a hack, but could work as a workaround.

[akryvko]

Not sure that it will help. Let me describe the case:

• we had 12 pods and each index configured with 3 replicas, so minIndexReplicas=3
• since our traffic is very spiky we wanted to be prepared for morning peak by increasing pods count and index replicas beforehand.
• so we updated pods to 18 and minIndexReplicas=5
• we expected that es-operator immediately change replica count right after configuration apply, but this not happened.
• so we had to manually update each index with "number_of_replicas" : 5 which is not quite convenient
• as we understood es operator applies minIndexReplicas only on "scale trigger", e.g. high cpu consumption. Which does not work for cases when we want to be pre-scaled.
  So we do not mind to have autoscaling, but also it would be good to apply minIndexReplicas to all indices immediately using config.

Here is our config:
https://github.bus.zalan.do/Phoenix/lounge-elasticsearch/blob/master/deploy/prod/apply/eds.yaml

[otrosien]

Closed via #157. Thank you for the contribution.