AntiAffinity values are not updated for canaries

[divanikus]

Describe the bug

I can't make the Canary to update antiaffinity setting for a deployment. My deployment is set to have one replica per host. I have 5 hosts and 3 replicas on them. But then I try to release a new version, promoted production Deployment have the same anitaffinity key as the Canary one. So I end up with failed releases because I do not have 6 hosts for now (3 for canary, 3 for production replicas).

Deployment is the following:

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: mc
    app.kubernetes.io/component: api
    app.kubernetes.io/instance: mc-master
    app.kubernetes.io/name: mc
    app.kubernetes.io/version: "7.1"
    branch: master
  name: mc-master-api
  namespace: production
spec:
  replicas: 3
  selector:
    matchLabels:
      app.kubernetes.io/component: api
      app.kubernetes.io/instance: mc-master
      app.kubernetes.io/name: mc-api
  strategy:
    rollingUpdate:
      maxSurge: 2
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: mc
        app.kubernetes.io/component: api
        app.kubernetes.io/instance: mc-master
        app.kubernetes.io/name: mc-api
        branch: master
        component: api
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app.kubernetes.io/name
                operator: In
                values:
                - mc-api
            topologyKey: kubernetes.io/hostname
      containers:
      - image: reducted/mc/mc:7.1
        imagePullPolicy: IfNotPresent
        name: mc
        ports:
        - containerPort: 8080
          name: http
          protocol: TCP
      dnsPolicy: ClusterFirst
      imagePullSecrets:
      - name: regcred
      restartPolicy: Always

And Canary for it:

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  labels:
    app: mc
    app.kubernetes.io/component: api
    app.kubernetes.io/instance: mc-master
    app.kubernetes.io/name: mc
    app.kubernetes.io/version: "7.1"
    branch: master
  name: mc-master-api
  namespace: production
spec:
  analysis:
    interval: 1m
    maxWeight: 100
    metrics:
    - interval: 1m
      name: request-success-rate
      thresholdRange:
        min: 95
    stepWeight: 20
    threshold: 20
  service:
    port: 8080
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: mc-master-api

Expected AntiAffinity block for mc-master-api-primary is the following:

      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app.kubernetes.io/name
                operator: In
                values:
                - mc-api-primary
            topologyKey: kubernetes.io/hostname

But in reality it is always just mc-api.

I've tried to rephrase the affinity verse, but without any luck.

Additional context

• Flagger version: 1.9.0
• Kubernetes version: 1.18.0
• Service Mesh provider: Linkerd 2.10.1
• Ingress provider: nginx

[stefanprodan]

Does it work if you remove the app: mc from your deployment template labels?

[divanikus]

Just checked. Nope, same thing.

[stefanprodan]

Have you deleted the deployments? the pod labels are immutable

[divanikus]

No, I've edited them. Also, you've said about template spec labels, and there they are mutable.

[stefanprodan]

Ok I've found the issue, here #805

So for Flagger to be able to patch the values you need to use the same name as your deployment mc-master-api.

[divanikus]

I think you should include that into the docs. It's not very intuitive right now.

[stefanprodan]

@divanikus from docs here https://docs.flagger.app/faq#is-pod-affinity-and-anti-affinity-supported

The value must match the name of the target deployment.

[stefanprodan]

Feel free to open a PR and improve the docs, thank you!

[divanikus]

Damn, I've read that section for several times and still missed it. Thanks.