Introduction

Canary deployments are a popular strategy for gradually rolling out changes to production applications. By releasing new features or updates to a small subset of users before making it available to everyone, canary deployments help minimize the impact of any potential issues or bugs. In this blog post, we’ll explore how to implement canary deployments for Java applications in Kubernetes.

Prerequisites

To follow along with the examples in this blog post, you’ll need:

1. A Kubernetes cluster up and running.
2. A Java application packaged as a Docker image and pushed to a container registry.
3. Basic knowledge of Kubernetes concepts and deployment configurations.

Step 1: Create Deployment Configurations

To implement canary deployments, we’ll create two separate Kubernetes deployments: one for the canary version and one for the stable version of our Java application.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-canary
spec:
  replicas: 1
  selector:
    matchLabels:
      app: myapp
      version: canary
  template:
    metadata:
      labels:
        app: myapp
        version: canary
    spec:
      containers:
        - name: myapp
          image: myapp:canary

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-stable
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      version: stable
  template:
    metadata:
      labels:
        app: myapp
        version: stable
    spec:
      containers:
        - name: myapp
          image: myapp:stable

In the above example, we have two deployments: myapp-canary and myapp-stable. The canary deployment (myapp-canary) has a replica count of 1 and uses the myapp:canary image, while the stable deployment (myapp-stable) has a replica count of 3 and uses the myapp:stable image.

Step 2: Create a Service for Load Balancing

To expose our Java application and load balance traffic across the canary and stable deployments, we’ll create a Kubernetes service.

apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    app: myapp
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8080
  type: LoadBalancer

In the example above, we create a service called myapp-service that selects pods with the app: myapp label. The service listens on port 8080 and forwards traffic to the pods on the same port.

Step 3: Implement Canary Traffic Splitting

To gradually route traffic to the canary version, we’ll use the Kubernetes Ingress resource and traffic splitting based on weight.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp-service
                port:
                  number: 8080
  ---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: myapp-canary-ingress
spec:
  rules:
    - http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp-service
                port:
                  number: 8080
  annotations:
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-weight: "10"

In the above example, we have defined two Ingress resources: myapp-ingress for the stable version and myapp-canary-ingress for the canary version. The nginx.ingress.kubernetes.io/canary annotation is set to “true” for the canary version, and the nginx.ingress.kubernetes.io/canary-weight annotation is set to “10” to specify that only 10% of the traffic will be routed to the canary version.

Conclusion

By following the steps outlined in this blog post, you can successfully implement canary deployments for Java applications in Kubernetes. Canary deployments allow you to test new features and updates in a controlled manner, reducing the risk of impacting all users. This strategy ensures a smooth transition to the new version while minimizing any potential issues. Happy deploying!

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