Blue-Green Deployment with Argo CD and Argo Rollouts

Introduction

Blue-Green deployment is a proven strategy to reduce downtime and risks associated with deploying new versions of applications. Using Argo Rollouts, you can implement a Blue-Green deployment strategy that allows last-minute functional tests on the new version to run before it starts serving production traffic. This blog explains configuring and testing Blue-Green deployment using Argo Rollouts, ensuring a seamless transition between application versions.

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Use Case

A customer wants to run functional tests on a new application version before it starts receiving production traffic. Using the Blue-Green deployment strategy in Argo Rollouts, users can:

Specify a preview service to route traffic to the new version.
Specify an active service to continue serving production traffic from the current version.
Pause the rollout to allow manual promotion of the new version.

With these features, users have full control over the deployment process, minimizing risks while ensuring the functionality and stability of the new release.

Key Components and Parameters

Active Service

The active service routes production traffic to the existing application version. It continues to serve traffic until the new version is manually promoted.

Preview Service

The preview service handles traffic routed to the new version for testing. This allows validation before promoting the new version to production.

AutoPromotionEnabled

Setting autoPromotionEnabled: false ensures that the deployment process pauses until manually promoted. Alternatively, autoPromotionSeconds can be used to delay automatic promotion for a specified duration.

Example Configuration:

Here is an example of a Blue-Green strategy with manual promotion enabled:

  strategy:
    blueGreen: 
      activeService: rollout-bluegreen-active
      previewService: rollout-bluegreen-preview
      autoPromotionEnabled: false

strategy:

blueGreen:

activeService: rollout-bluegreen-active

previewService: rollout-bluegreen-preview

autoPromotionEnabled: false

Step-by-Step Workflow

Initial Deployment

When deploying a new image using the Blue-Green strategy:

New pods are created with the updated image.
Old pods continue to serve production traffic via the active service.
New pods are routed through the preview service for testing.

Testing the New Version

Users can test the new version by accessing the preview service. The rollout process remains paused until the user manually promotes the new version.

Manual Promotion

Once satisfied with the new version, the user can promote it:

kubectl argo rollouts promote <rollout-name> -n <namespace>

1	kubectl argo rollouts promote <rollout-name> -n <namespace>

After promotion:

The new version replaces the old version as the active service.
The old pods are deleted.
The new version serves production traffic.

Testing commands

Here are some essential commands to monitor and manage the rollout:

List all pods:

kubectl get po -n <namespace> --owide

1	kubectl get po -n <namespace> --owide

Check endpoints:

kubectl get ep -n <namespace>

1	kubectl get ep -n <namespace>

Get rollout details:

kubectl argo rollouts get rollout <rollout-name> -n <namespace>

1	kubectl argo rollouts get rollout <rollout-name> -n <namespace>

Promote the new version:

kubectl argo rollouts promote <rollout-name> -n <namespace>

1	kubectl argo rollouts promote <rollout-name> -n <namespace>

Visualizing with Argo Rollouts Dashboard

To enhance the monitoring experience, Argo Rollouts provides a dashboard:

Expose the dashboard:

kubectl argo rollouts dashboard

1	kubectl argo rollouts dashboard

This exposes the dashboard on port 3100. Access it via a browser to get a detailed view of the rollout status, including traffic distribution and pod statuses.

Example Rollout Configuration

Here is a sample Blue-Green Rollout configuration file:

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollout-bluegreen
spec:
  replicas: 2
  revisionHistoryLimit: 2
  selector:
    matchLabels:
      app: rollout-bluegreen
  template:
    metadata:
      labels:
        app: rollout-bluegreen
    spec:
      containers:
      - name: rollouts-demo
        image: argoproj/rollouts-demo:blue
        imagePullPolicy: Always
        ports:
        - containerPort: 8080
  strategy:
    blueGreen: 
      activeService: rollout-bluegreen-active
      previewService: rollout-bluegreen-preview
      autoPromotionEnabled: false

---
kind: Service
apiVersion: v1
metadata:
  name: rollout-bluegreen-active
spec:
  selector:
    app: rollout-bluegreen
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080


---
kind: Service
apiVersion: v1
metadata:
  name: rollout-bluegreen-preview
spec:
  selector:
    app: rollout-bluegreen
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080

apiVersion: argoproj.io/v1alpha1

kind: Rollout

metadata:

spec:

replicas: 2

revisionHistoryLimit: 2

selector:

matchLabels:

app: rollout-bluegreen

template:

metadata:

labels:

app: rollout-bluegreen

spec:

containers:

- name: rollouts-demo

image: argoproj/rollouts-demo:blue

imagePullPolicy: Always

ports:

- containerPort: 8080

strategy:

blueGreen:

activeService: rollout-bluegreen-active

previewService: rollout-bluegreen-preview

autoPromotionEnabled: false

---

kind: Service

apiVersion: v1

metadata:

spec:

selector:

app: rollout-bluegreen

ports:

- protocol: TCP

port: 80

targetPort: 8080

---

kind: Service

apiVersion: v1

metadata:

spec:

selector:

app: rollout-bluegreen

ports:

- protocol: TCP

port: 80

targetPort: 8080

Here, once we deploy the manifest of the services and Rollout

The application will be deployed, and both services will be mapped to the same application to serve for the first time.
Once the newer image is updated, it creates a newer version pod, and traffic will be served from the previewService, and the old pod will continue to serve the traffic from the active service.
Once the testing is done on the newer version, the user can promote it to the newer version and deploy the application.
Once the application is deployed, you can observe new pods starting to serve the traffic using newer versions. This can be observed by describing the service or listing the endpoints of the service using the above testing commands.

Benefits of Blue-Green Deployment with Argo Rollouts

Reduced Risk: Traffic can be tested in a controlled environment before promotion.
Enhanced Control: Manual promotion ensures no untested versions are deployed to production.
Seamless Rollback: In case of issues, you can easily revert to the previous version.

References

Blue-Green deployment using Argo Rollouts is an excellent choice for ensuring smooth application upgrades with minimal disruption. Following the steps outlined in this blog, you can confidently manage deployments and maintain high availability for your applications.

Conclusion

Implementing a Blue-Green deployment strategy using Argo Rollouts ensures smooth and controlled application updates with minimal downtime. By leveraging preview and active services, you can safely test new releases before they reach production.

Manual promotion further enhances reliability, allowing users to validate changes before full rollout. With the added visualization and monitoring capabilities of the Argo Rollouts dashboard, tracking deployments become more efficient, ultimately leading to a stable and resilient application lifecycle.

Drop a query if you have any questions regarding Blue-Green deployment and we will get back to you quickly.

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FAQs

1. How can I roll back to the previous version if issues occur after promotion?

ANS: – You can roll back to the previous version using the following command:

kubectl argo rollouts undo rollout <rollout-name> -n <namespace>

1	kubectl argo rollouts undo rollout <rollout-name> -n <namespace>

This reverts the deployment to the previous stable version.

2. Can I automate the promotion of the new version instead of manual intervention?

ANS: – Yes, by setting autoPromotionEnabled: true or configuring autoPromotionSeconds, the rollout can automatically promote the new version after a specified time delay without manual approval.

WRITTEN BY Ravikumar Eranna Murali

Ravikumar works as a Sr. Research Associate at CloudThat. His expertise lies in AWS Services and pursuing DevOps technologies like Kubernetes, Docker, and Jenkins. Ravi enjoys learning and working on new challenges to give the best solution.