Exposing scale subresource to enable HPA's to modify the replicas of Infinispan CR

[ZeidH]

Enhanced the spec.subresources field for the Infinispan CRD to map scaling

      scale:
        specReplicasPath: .spec.replicas
        statusReplicasPath: .status.replicas

This enables APIs like the HorizontalPodAutoscaler and KEDA to modify the replica count of the Cache.

[openshift-ci[bot]]

Hi @ZeidH. Thanks for your PR.

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[ZeidH]

Thanks for the clear instructions @ryanemerson!, I'm rather new to this so appreciate the help. Encountered this issue with controller-gen on my version of go (1.22.5) so I also updated it to latest (1.15.0).

[ryanemerson]

Thanks for updating @ZeidH. It seems like we need to increase our baseline go version in order to use that version of controller-gen. I have created a PR to baseline on 1.21 (1.20 is now EOL) and update the controller-gen version https://github.com/infinispan/infinispan-operator/pull/2134. I'll let you know once that PR has been merged so that you can rebase this PR.

[ZeidH]

I've tested the autoscaling with this setup:

./scripts/ci/kind-with-olm.sh
make deploy-cert-manager
helm install keda kedacore/keda --namespace keda --create-namespace
skaffold dev

and a ScaledObject that targets the Infinispan CR

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: infinispan-scaler
  namespace: infinispan-operator-system
spec:
  minReplicaCount: 0
  scaleTargetRef:
    apiVersion: infinispan.org/v1
    kind: Infinispan
    name: test-cache
  triggers:
    - metadata:
        desiredReplicas: '2'
        start: 52 8 * * *
        end: 59 8 * * *
        timezone: UTC
      type: cron
---
apiVersion: infinispan.org/v1
kind: Infinispan
metadata:
  annotations:
    infinispan.org/monitoring: 'true'
    infinispan.org/operatorPodTargetLabels: 'rht.comp,rht.comp_ver,rht.prod_name,rht.prod_ver,rht.subcomp_t'
  name: test-cache
  namespace: infinispan-operator-system
spec:
  service:
    container:
      livenessProbe:
        failureThreshold: 5
        initialDelaySeconds: 0
        periodSeconds: 10
        successThreshold: 1
        timeoutSeconds: 1
      readinessProbe:
        failureThreshold: 5
        initialDelaySeconds: 0
        periodSeconds: 10
        successThreshold: 1
        timeoutSeconds: 1
      startupProbe:
        failureThreshold: 600
        initialDelaySeconds: 3
        periodSeconds: 1
        successThreshold: 1
        timeoutSeconds: 1
    type: DataGrid
  jmx: {}
  configListener:
    enabled: true
    logging:
      level: info
  upgrades:
    type: Shutdown
  replicas: 1

The Statefulset was able to scale from zero to n and back but I can imagine that for some configurations scaling to zero is not possible

[ryanemerson]

Apologies for the delay @ZeidH, but main is now baselined on go 1.21. Can you please rebase on the latest code?

[ryanemerson]

but I can imagine that for some configurations scaling to zero is not possible

Can you explain which configurations you think would cause issues?

[ZeidH]

but I can imagine that for some configurations scaling to zero is not possible

Can you explain which configurations you think would cause issues?

I can't think of any specific to Infinispan, the amount of available configurations is so immense it would take a long time to figure out what config can be autoscaled, and what cannot. I think after learning a bit on what Infinispan does the past few months, the configs where autoscaling doesn't work well also most likely wouldn't make much sense to use autoscaling/scale to zero, like clustered caches where you (almost)always want to have a hot instance.

But from experience there can be issues with autoscaling when using specific types of storage configurations, or as @rigazilla mentioned in the GH Issue: about the operator sometimes needs to explicitly set the .spec.Replicas, i.e. in upgrade

What we attempted to do is to dynamically scale a replicated cache with the amount of nodes (1 cache per node), essentially making Infinispan behave like a DaemonSet. Although we're not done with it just yet, so far it's been working out well.

[ryanemerson]

Thanks @ZeidH and sorry for the delay. I'll create a follow up PR with some documentation. Let me know if you need this feature soon via OLM and I can expedite the next release.