In a microservices architecture, deploying applications on Kubernetes has become a popular choice due to its scalability and ease of management. However, sometimes deployments may fail, resulting in downtime and impacting user experience. To mitigate this, it is crucial to have an automated rollback mechanism in place.

In this blog post, we will explore how to implement automated rollback for failed Java app deployments on Kubernetes using a sample Java application. We will leverage Kubernetes native features and tools to achieve this.

Prerequisites

To follow along, ensure you have the following prerequisites:

• Kubernetes cluster up and running
• kubectl command line tool installed and configured to access your cluster
• A sample Java application packaged as a Docker image

Deploying the Java App on Kubernetes

Before we can implement automated rollback, let’s first deploy our Java application on Kubernetes. Here’s an example deployment.yaml file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: my-app:latest
        ports:
        - containerPort: 8080

Create the deployment by running the following command:

kubectl apply -f deployment.yaml

Once deployed, the application will be accessible through a Kubernetes service or an ingress resource.

Monitoring and Detecting Deployment Failures

To implement automated rollback, we need a way to monitor and detect deployment failures. One approach is to use Kubernetes liveness and readiness probes. By setting up appropriate probes, we can continuously monitor the health of our application.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: my-app:latest
        ports:
        - containerPort: 8080
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 5
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5

With these probes configured, Kubernetes will periodically make HTTP requests to the /health endpoint of our application. If the probe fails, indicating that the deployment has failed, Kubernetes will mark the pod as unhealthy.

Implementing Automated Rollback

To implement the automated rollback, we can leverage Kubernetes native feature called Rolling Updates and Rollbacks.

To roll back to the previous stable version of the app, run the following command:

kubectl rollout undo deployment/my-app

To automate this rollback process, we can write a script or use a continuous integration/continuous deployment (CI/CD) tool like Jenkins or GitLab CI/CD pipelines.

The script or CI/CD pipeline should include logic to monitor the deployment status. If a failure is detected, the rollback command should be executed.

Conclusion

Having an automated rollback mechanism is crucial to ensure the stability and reliability of your Java application deployments on Kubernetes. By leveraging Kubernetes probes and rolling updates/rollbacks, you can minimize downtime and provide a better user experience.

Implementing automated rollback requires careful monitoring and a well-thought-out deployment strategy. With the right tools and processes in place, you can make your Java app deployments on Kubernetes more resilient and robust.

#DevOps #Kubernetes