In this article, we will learn how to automate Blue/Green Deployment on Kubernetes with Argo Rollouts.
Argo Rollouts is a Kubernetes Controller and set of Custom Resource Definitions (CRDs) that provide advanced features for application deployment on Kubernetes compared to the native Kubernetes Deployment Object.
Argo Rollouts provide deployment capabilities such as blue-green, canary, canary analysis, experimentation, and progressive delivery features to Kubernetes.
Because Argo Rollouts are a set of CRDs, we need to install them into the Kubernetes Cluster. Run the following commands to install Argo Rollouts.
kubectl create namespace argo-rollouts namespace/argo-rollouts created
kubectl apply -n argo-rollouts -f https://github.com/argoproj/argo-rollouts/releases/latest/download/install.yaml customresourcedefinition.apiextensions.k8s.io/analysisruns.argoproj.io created customresourcedefinition.apiextensions.k8s.io/analysistemplates.argoproj.io created customresourcedefinition.apiextensions.k8s.io/clusteranalysistemplates.argoproj.io created customresourcedefinition.apiextensions.k8s.io/experiments.argoproj.io created customresourcedefinition.apiextensions.k8s.io/rollouts.argoproj.io created serviceaccount/argo-rollouts created clusterrole.rbac.authorization.k8s.io/argo-rollouts created clusterrole.rbac.authorization.k8s.io/argo-rollouts-aggregate-to-admin created clusterrole.rbac.authorization.k8s.io/argo-rollouts-aggregate-to-edit created clusterrole.rbac.authorization.k8s.io/argo-rollouts-aggregate-to-view created clusterrolebinding.rbac.authorization.k8s.io/argo-rollouts created secret/argo-rollouts-notification-secret created service/argo-rollouts-metrics created deployment.apps/argo-rollouts created
Check if we installed it successfully.
kubectl get pod -n argo-rollouts
NAME READY STATUS RESTARTS AGE argo-rollouts-76fcfc8d7f-k6mth 1/1 Running 0 58s
Argo Rollouts Deployment Strategy
To use Argo Rollouts, we declare a resource with the apiVersion attribute as
argoproj.io/v1alpha1 and the kind as
Rollout, like below:
apiVersion: argoproj.io/v1alpha1 kind: Rollout
The configuration of Argo Rollouts has a strategy property for us to choose the deployment strategy we want, with two values of blueGreenand canary.
See detail here Rollout Specification. Don’t try to understand all properties for now.
In this article, we will learn about blue/green.
I use Minikube to run Kubernetes Cluster for the demo. Create a file named
apiVersion: argoproj.io/v1alpha1 kind: Rollout metadata: name: bluegreen-demo labels: app: bluegreen-demo spec: replicas: 2 revisionHistoryLimit: 1 selector: matchLabels: app: bluegreen-demo template: metadata: labels: app: bluegreen-demo spec: containers: - name: bluegreen-demo image: argoproj/rollouts-demo:green imagePullPolicy: Always ports: - name: http containerPort: 8080 protocol: TCP strategy: blueGreen: autoPromotionEnabled: false activeService: bluegreen-demo previewService: bluegreen-demo-preview
All properties of Rollout are the same as a native Deployment Object, only the strategy attribute is different. In the file above, we declare 3 properties:
autoPromotionEnabled: false- Indicates if the rollout should automatically promote the new ReplicaSet to the active service or enter a paused state. If not specified, the default value is true.
activeService: bluegreen-demo- Reference to service that the rollout modifies as the active service.
previewService: bluegreen-demo-preview- Name of the service that the rollout modifies as the preview service.
Next, we create a file named
apiVersion: v1 kind: Service metadata: name: bluegreen-demo labels: app: bluegreen-demo spec: type: NodePort selector: app: bluegreen-demo ports: - port: 80 targetPort: http protocol: TCP name: http --- apiVersion: v1 kind: Service metadata: name: bluegreen-demo-preview labels: app: bluegreen-demo spec: type: NodePort selector: app: bluegreen-demo ports: - port: 80 targetPort: http protocol: TCP name: http
The two Services properties are the same except for the name property. Next, we create a Rollout Object.
kubectl apply -f bluegreen-rollout.yaml rollout.argoproj.io/bluegreen-demo created
kubectl get rollout NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE bluegreen-demo 2 2 2 2 30s
When we create a Rollout, the Argo Rollouts implicit create a ReplicaSet for a current revision. Let’s check:
kubectl get rs NAME DESIRED CURRENT READY AGE bluegreen-demo-fbc7b7f55 2 2 2 4m37s
kubectl get pod NAME READY STATUS RESTARTS AGE bluegreen-demo-fbc7b7f55-g6fst 1/1 Running 0 37s bluegreen-demo-fbc7b7f55-vvdth 1/1 Running 0 37s
Ensure that Replica Set and Pod are running, next, we create a Service.
kubectl apply -f service.yaml service/bluegreen-demo created service/bluegreen-demo-preview created
At this time, both the
bluegreen-demo-preview are pointing to the same ReplicaSet as
Let’s test, we run the following commands to get the URL of both services.
minikube service bluegreen-demo --url 172.26.123.245:30000
minikube service bluegreen-demo-preview --url 172.26.123.245:30001
Open the browser, we will see the UI below.
Now, we change the
image property of Rollout Object.
... spec: containers: - name: bluegreen-demo image: argoproj/rollouts-demo:blue ...
Updating Rollout Object.
kubectl apply -f bluegreen-rollout.yaml rollout.argoproj.io/bluegreen-demo configured
At this point, Argo Rollouts will create a new ReplicaSet for the new configuration.
kubectl get rs bluegreen-demo-7d6459646d 2 2 2 2m11s bluegreen-demo-fbc7b7f55 2 2 2 41m
kubectl get pod NAME READY STATUS RESTARTS AGE bluegreen-demo-7d6459646d-2zm56 1/1 Running 0 2m13s bluegreen-demo-7d6459646d-xz9bj 1/1 Running 0 2m13s bluegreen-demo-fbc7b7f55-g6fst 1/1 Running 0 41m bluegreen-demo-fbc7b7f55-vvdth 1/1 Running 0 41m
bluegreen-demo-preview service is modified to point to the new ReplicaSet. Accessing the preview service address will see a different UI.
bluegreen-demo service does not change.
After we check the new ReplicaSet and see that all is well, next, we promote the new revision of ReplicaSet by updating the
bluegreen-demo service to point to it, we run the following command (don’t follow, we will use another way).
kubectl argo rollouts promote bluegreen-demo rollout 'bluegreen-demo' promoted
Now, Argo Rollouts update the
bluegreen-demo service to point to the new ReplicaSet, after waiting (default 30 seconds), the old ReplicaSet is scaled down.
In my opinion, DevOps Engineers should not do the work “promotes” the new ReplicaSet, our task is just to build the CI/CD so that the Rollout can be updated when a new version of the application is available. Leave it to QC Engineer.
But QC can’t run CLI so we need to have a dashboard for QC to do this. Fortunately, Argo Rollout provides us with a dashboard, which we can enable using kubectl or using
quay.io/argoproj/kubectl-argo-rollouts container image.
kubectl argo rollouts dashboard INFO Argo Rollouts Dashboard is now available at localhost 3100
localhost:3100 we will see the dashboard of Argo Rollouts.
You will see the Promote button, the person who clicks this button will be the QC, if anything is wrong, the QC will be responsible =)))), let’s click on the promote button.
Now you access both the
bluegreen-demo and the
bluegreen-demo-preview service we will see the same UI.
Ingress configuration for public access if you need.
apiVersion: networking.k8s.io/v1beta1 kind: Ingress metadata: name: bluegreen-demo annotations: ingress.kubernetes.io/proxy-body-size: 100M kubernetes.io/ingress.class: nginx ingress.kubernetes.io/app-root: / spec: rules: - host: blue-green.example.com http: paths: - path: / backend: serviceName: bluegreen-demo servicePort: 80 --- apiVersion: networking.k8s.io/v1beta1 kind: Ingress metadata: name: bluegreen-demo-preview annotations: ingress.kubernetes.io/proxy-body-size: 100M kubernetes.io/ingress.class: nginx ingress.kubernetes.io/app-root: / spec: rules: - host: blue-green-preview.example.com http: paths: - path: / backend: serviceName: bluegreen-demo-preview servicePort: 80
So we have learned how to automate Blue/Green Deployment with Argo Rollouts, as you can see, it’s also simple 😁. If you have any questions or need further clarification, you can ask in the comment section below.
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