Kubernetes Blue Green Deploy
Deploy the new version to the stage pod set and wait for it to reach steady state before a traffic swap.
The Kubernetes Blue Green Deploy step creates or updates the stage pod set with the new version of your application alongside the existing pod set that serves production traffic. The primary service continues routing all production traffic to the existing pod set until the swap step runs.
Before you begin
Before you configure the step, make sure you have the following in place:
A Kubernetes service: Go to Kubernetes services to set up service manifests and artifact source.
A Kubernetes infrastructure: Go to Kubernetes infrastructure to connect your cluster and namespace.
A Harness delegate in target cluster: The delegate runs deployment steps in the cluster.
Runtime configuration: Every Kubernetes stage requires a
runtimeblock specifying connector and namespace. Go to Kubernetes runtime configuration to understand the required fields.
Configure the step
The following parameters are available on the Kubernetes Blue Green Deploy step.
Name
Display name for this step in the stage canvas. Default: Kubernetes Blue Green Deploy.
Required
Skip Dry Run
When enabled, Harness skips the kubectl apply --dry-run pre-validation before applying. Default: false.
Optional
Kubernetes Pruning
When enabled, Harness removes resources from the cluster that exist in the previous release but are no longer in the current manifests. Default: false.
Optional
Skip Unchanged Manifest
When enabled, Harness compares rendered manifests with the previous deployment and skips the step if no changes are detected. Default: false.
Optional
Use Traffic Shift
When enabled, Harness activates traffic routing configuration on this step to split live traffic between primary and stage services.
Optional
Manifest Path
Override the manifest paths from the service configuration. Leave empty to use all manifests from the service.
Optional
Kubeconfig Path
Path to the kubeconfig file. Default: ${{infra.kube_config_path}}.
Optional
Namespace
Target namespace. Default: ${{infra.namespace}}.
Optional
Release Name
Name used to track Harness release history. Default: ${{infra.releaseName}}.
Optional
Log Level
Verbosity of step logs. Default: info.
Optional
ONE WORKLOAD PER BLUE-GREEN STAGE
Blue-green deployments support exactly one Kubernetes Deployment workload per stage. If your service manifests define multiple Deployment objects, the stage fails.
How the step works
When the step runs, it performs three internal actions:
Kubernetes Blue Green Prepare Action: Reads your manifests, determines the stage color (the inverse of the current primary color), creates or updates the stage service, labels the new pod set with
harness.io/color: <stage-color>, and writes the prepared manifests to the workspace. Harness does not modify the primary service at this point.Kubernetes Apply Action: Applies the prepared manifests using
kubectl apply. This creates the new pod set alongside the existing pod set, with both running simultaneously. The primary service continues routing all production traffic to the existing pod set.Kubernetes Steady State Check Action: Polls the cluster until all pods in the new deployment reach
Runningstatus and pass readiness checks, or until the step timeout is reached.
Traffic routing configuration
When you enable Use Traffic Shift, a traffic routing section appears on the step. The following fields control how Harness splits live traffic between primary and stage services:
Traffic Shift Command Timeout
Maximum time Harness waits for the traffic shift operation to complete. Default: 5m.
Provider
The traffic management provider: istio (creates an Istio VirtualService) or k8s-native (uses a Kubernetes HTTPRoute).
Resource Name
Name of the VirtualService or HTTPRoute resource.
Hosts
Hostnames the routing rules apply to.
Gateways
Istio gateway names to attach the VirtualService to. Required for external traffic when using Istio.
Configure Routes
Weighted route definitions splitting traffic between primary and stage destinations. Weights across all routes must sum to 100.
Step outputs
The following output variables are available for use in downstream steps.
stableService
The name of the service currently serving production traffic. Auto-populates the Swap Services step.
stageService
The name of the service currently serving stage traffic. Auto-populates the Swap Services step.
isOpenshift
Whether the deployment targets an OpenShift cluster.
Advanced settings
Timeout duration: Maximum time the step is allowed to run before Harness terminates it.
On failure: Define what happens if the step fails, such as retry, mark as success, or abort.
Strategy: Configure a looping strategy to run this step over a list of values.
Conditional execution: Run this step only when a specified condition is true.
Next steps
Go to Kubernetes blue-green deployment to understand the full blue-green deployment flow.
Go to Kubernetes Blue Green Swap Services Selectors to configure the step that routes production traffic to the new pod set.
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