PodDisruptionBudget calculation is not working? about consul-helm

[Typositoire]

I had to manually delete the PDB and recreate it as you can't update a PDB.

[adilyse]

@Typositoire In this case, this is the expected behavior. It is recommended to run with 3-5 Consul servers, so this calculation gives the desired value of 0 allowed voluntary disruptions with 3 server replicas.

As for the calculation itself, the behavior is a bit unintuitive since it's using integer division, which evaluations 3/2 as 1. We've accounted for this, though, so the calculation is correct.

Hopefully that answers your question!

[Typositoire]

The problem happens during rolling upgrades.

Given 3 nodes with 1 consul-server each. I can never upgrade gracefully as this would go against the PDB (node drain). In a setup with KOPS this is what is happening and this is annoying.

With 3 nodes you can survive a 1 node failure, I'm not sure why you force it to be 0.

[Typositoire]

I1204 14:49:44.381510   13119 request.go:874] Response Body: {"kind":"Status","apiVersion":"v1","metadata":{},"status":"Failure","message":"Cannot evict pod as it would violate the pod's disruption budget.","reason":"TooManyRequests","details":{"causes":[{"reason":"DisruptionBudget","message":"The disruption budget consul-server needs 3 healthy pods and has 3 currently"}]},"code":429}
I1204 14:49:49.382064   13119 request.go:874] Request Body: {"kind":"Eviction","apiVersion":"policy/v1beta1","metadata":{"name":"consul-server-1","namespace":"consul","creationTimestamp":null},"deleteOptions":{}}

[adilyse]

Thank you for the additional information! I'll do some more digging and see what we can do about this.

[s3than]

@adilyse I've been chasing this issue up today as well, It appears that the sprig library doesn't currently support floats so what happens is the following

3/2 = 1
1-1 = 0
ceil(0) = 0

My current fix is as below, I can put together a pull request and update tests for you hopefully this evening.
{{- define "consul.pdb.maxUnavailable" -}} {{- if eq (int .Values.server.replicas) 1 -}} {{ 0 }} {{- else if .Values.server.disruptionBudget.maxUnavailable -}} {{ .Values.server.disruptionBudget.maxUnavailable -}} {{- else -}} {{- div (sub (div (mul (int .Values.server.replicas) 10) 2) 1) 10 -}} {{- end -}} {{- end -}}

[s3than]

@adilyse Hopefully this solves this issue I implemented something different for the calculations and provided tests.

Any problems let me know