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Skip Harness label selector tracking on Kubernetes deployments


Currently, this feature is behind the feature flag SKIP_ADDING_TRACK_LABEL_SELECTOR_IN_ROLLING. Contact Harness Support to enable the feature.

You can prevent Harness from using its default Kubernetes label selector, stable, during canary deployments. Skipping this label can help when you have existing, non-Harness deployed services or naming conflicts.

Labels in Harness Kubernetes canary phases

Default Harness Kubernetes canary deployments are a two-phase process that relies on deployment object labels for tracking.

  1. Canary Phase

    1. Harness creates a canary version of the Kubernetes deployment object defined in your service definition Manifests section.
    2. All pods in the canary phase have the label canary. Traffic could be routed to these pods using this label.
    3. Once this deployment is verified, the canary delete step deletes the deployment by default.

    Using this method, Harness provides a canary pod set as a way to test the new build, run your verification.

  2. Primary Phase

    1. Runs the actual deployment using a Kubernetes rolling update with the number of pods you specify in the Manifests files. For example, replicas: 3.
    2. All pods in the primary phase have the label stable.

Invalid value LabelSelector

Kubernetes labels are immutable. If a specific deployment object already exists in the cluster, you cannot change its labels.

If the deployment object already exists before the Harness deployment, it might conflict with the default Harness Kubernetes canary deployment due to the use of the label

If you are deploying different Harness deployment objects to the same cluster, you might encounter a selector error.

The Deployment “harness-example-deployment” is invalid: spec.selector:   
Invalid value: v1.LabelSelector{MatchLabels:map[string]string{“app”:“harness-example”},
MatchExpressions:[]v1.LabelSelectorRequirement{}}: field is immutable

Most often, you can delete or rename the deployment object. In some cases, you will experience downtime when the object restarts.

As an alternative, you can force Harness to skip the stable label in the canary deployment.

Skipping the tracking label

Once the relevant feature flag is enabled, a Harness Kubernetes canary deployment works like this:

  • If the deployment object already exists in the cluster without the stable label, Harness will not add the stable label to the deployment object.
  • If the deployment object already exists with the stable label, Harness will not delete it.
  • For any new deployment object, Harness will not add the stable label.