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    Container Service for Kubernetes:Use HPA for applications

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    Container Service for Kubernetes:Use HPA for applications

    Last Updated:Mar 26, 2026

    Argo CD periodically synchronizes your Git repository with the cluster, which may conflict with pod scaling activities performed by the Horizontal Pod Autoscaler (HPA)—including overwriting spec.replicas with whatever value is in the manifest. To prevent this conflict, exclude spec.replicas from Argo CD's sync scope. The method depends on the application's default replica count.

    Applications with one replica by default

    Comment out the replicas field in the Deployment manifest. Argo CD only syncs fields that are present in Git, so omitting replicas lets HPA manage it exclusively.

    apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  # do not include replicas in the manifests if you want replicas to be controlled by HPA
  # replicas: 1
  template:
    spec:
      containers:
      - image: nginx:1.7.9
        name: nginx
        ports:
        - containerPort: 80
...

    Applications with multiple replicas by default

    When your manifest declares more than one replica, commenting out the field breaks the default behavior. Instead, configure Argo CD to ignore differences in spec.replicas using Diffing Customization. Argo CD then leaves that field alone during sync, letting HPA control replica counts without interference.

    Two scopes are available: application-level (affects one application) and system-level (affects all applications in a Fleet instance).

    Application-level configuration

    Configure .spec.ignoreDifferences in the Application resource. This affects only the specified application.

    By default, the rule applies to all Deployments in the application. To target a specific Deployment, uncomment and set the name and namespace fields.

    The group field refers to the Kubernetes API group without the version (for example, apps, not apps/v1).
    apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: app-test
  namespace: argocd
spec:
  ignoreDifferences:
  - group: apps
    kind: Deployment
    #name: test
    #namespace: default
    jsonPointers:
    - /spec/replicas
  ...

    System-level configuration

    Configure the argocd-cm ConfigMap to ignore spec.replicas across all applications in the Fleet instance. Use this when you want HPA to control replica counts for every managed application.

    For ACK One GitOps, controlplane-kcm must be configured alongside kube-controller-manager in managedFieldsManagers.

    apiVersion: v1
data:
  ...
  resource.customizations.ignoreDifferences.all: |
    managedFieldsManagers:
    - kube-controller-manager
    - controlplane-kcm
    jsonPointers:
    - /spec/replicas
kind: ConfigMap
metadata:
  name: argocd-cm
  namespace: argocd

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