Topology Spread Constraint support

[zamsong123]

What did you do to encounter the bug? Steps to reproduce the behavior: When I install the helm chart on EKS, I can't find the "topologySpreadConstraints:" related config

What did you expect? When we deploy the helm chart to the AWS EKS env, we want the pods to run on different Availability Zone.

What happened instead? They are not running on separate AZ

Screenshots If applicable, add screenshots to help explain your problem.

Kubernetes Cluster Information

• Distribution
• Version
• Image Registry location (quay, or an internal registry)

Additional context Add any other context about the problem here.

If possible, please include:

• kubectl describe output
• yaml definitions for your objects
• log files for the operator and database pods

[zamsong123]

I will make a contribution to this issue. starting now

[zamsong123]

did some testing as below:
sample-app % helm template .
---
# Source: sample-app/templates/serviceaccount.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: release-name-sample-app
  labels:
    helm.sh/chart: sample-app-0.1.0
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "0.1.0"
    app.kubernetes.io/managed-by: Helm
---
# Source: sample-app/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: release-name-sample-app-frontend
  labels:
    helm.sh/chart: sample-app-0.1.0
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "0.1.0"
    app.kubernetes.io/managed-by: Helm
    app: release-name-sample-app-frontend
spec:
  type: ClusterIP
  ports:
    - port: 3000
      targetPort: http
      protocol: TCP
      name: http
  selector:
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app: release-name-sample-app-frontend
---
# Source: sample-app/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: release-name-sample-app-backend
  labels:
    helm.sh/chart: sample-app-0.1.0
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "0.1.0"
    app.kubernetes.io/managed-by: Helm
    app: release-name-sample-app-backend
spec:
  type: ClusterIP
  ports:
    - port: 8000
      targetPort: http
      protocol: TCP
      name: http
  selector:
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app: release-name-sample-app-backend
---
# Source: sample-app/templates/deployment-backend.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: release-name-sample-app-backend
  labels:
    helm.sh/chart: sample-app-0.1.0
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "0.1.0"
    app.kubernetes.io/managed-by: Helm

spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: sample-app
      app.kubernetes.io/instance: release-name
      app: release-name-sample-app-backend
  template:
    metadata:
      labels:
        app.kubernetes.io/name: sample-app
        app.kubernetes.io/instance: release-name
        app: release-name-sample-app-backend
    spec:
      serviceAccountName: release-name-sample-app
      topologySpreadConstraints:
        - labelSelector:
            matchExpressions:
            - key: app
              operator: In
              values:
              - mangodb1
          maxSkew: 1
          topologyKey: topology.kubernetes.io/zone
          whenUnsatisfiable: DoNotSchedule
      securityContext:
        {}
      containers:
        - name: sample-app
          securityContext:
            {}
          image: "quay.io/mongodb/farm-intro-backend:0.1"
          imagePullPolicy: Always
          command:
            - python3
            - main.py
          ports:
            - name: http
              containerPort: 8000
              protocol: TCP
          env:
            - name: DB_URL
              valueFrom:
                secretKeyRef:
                  name: <resource-name>-<database>-<user>
                  key: connectionString.standard
            - name: DB_NAME
              value: 'admin'
          resources:
            {}
---
# Source: sample-app/templates/deployment-frontend.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: release-name-sample-app-frontend
  labels:
    helm.sh/chart: sample-app-0.1.0
    app.kubernetes.io/name: sample-app
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "0.1.0"
    app.kubernetes.io/managed-by: Helm
    app: release-name-sample-app-frontend
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: sample-app
      app.kubernetes.io/instance: release-name
      app: release-name-sample-app-frontend
  template:
    metadata:
      labels:
        app.kubernetes.io/name: sample-app
        app.kubernetes.io/instance: release-name
        app: release-name-sample-app-frontend
    spec:
      serviceAccountName: release-name-sample-app
      topologySpreadConstraints:
        - labelSelector:
            matchExpressions:
            - key: app
              operator: In
              values:
              - mangodb1
          maxSkew: 1
          topologyKey: topology.kubernetes.io/zone
          whenUnsatisfiable: DoNotSchedule
      securityContext:
        {}
      containers:
        - name: sample-app
          securityContext:
            {}
          image: "quay.io/mongodb/farm-intro-frontend:0.1"
          imagePullPolicy: Always
          ports:
            - name: http
              containerPort: 3000
              protocol: TCP
          env:
          - name: DANGEROUSLY_DISABLE_HOST_CHECK
            value: 'true'
          - name: SVC_BACKEND
            value: release-name-sample-app-backend:8000

          resources:
            {}

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