Add exercise for canary deployment

c.pod_design.md

@@ -520,6 +520,148 @@ kubectl delete deploy/nginx hpa/nginx
 </p>
 </details>
 
+### Implement canary deployment by running two instances of nginx marked as version=v1 and version=v2 so that the load is balanced at 75%-25% ratio
+
+<details><summary>show</summary>
+<p>
+
+Deploy 3 replicas of v1:
+```
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: my-app-v1
+  labels:
+    app: my-app
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app: my-app
+      version: v1
+  template:
+    metadata:
+      labels:
+        app: my-app
+        version: v1
+    spec:
+      containers:
+      - name: nginx
+        image: nginx
+        ports:
+        - containerPort: 80
+        volumeMounts:
+        - name: workdir
+          mountPath: /usr/share/nginx/html
+      initContainers:
+      - name: install
+        image: busybox:1.28
+        command:
+        - /bin/sh
+        - -c
+        - "echo version-1 > /work-dir/index.html"
+        volumeMounts:
+        - name: workdir
+          mountPath: "/work-dir"
+      volumes:
+      - name: workdir
+        emptyDir: {}
+```
+
+Create the service:
+```
+apiVersion: v1
+kind: Service
+metadata:
+  name: my-app-svc
+  labels:
+    app: my-app
+spec:
+  type: ClusterIP
+  ports:
+  - name: http
+    port: 80
+    targetPort: 80
+  selector:
+    app: my-app
+```
+
+Test if the deployment was successful:
+```bash
+curl $(kubectl get svc my-app-svc -o jsonpath="{.spec.clusterIP}")
+version-1
+```
+
+Deploy 1 replica of v2:
+```
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: my-app-v2
+  labels:
+    app: my-app
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: my-app
+      version: v2
+  template:
+    metadata:
+      labels:
+        app: my-app
+        version: v2
+    spec:
+      containers:
+      - name: nginx
+        image: nginx
+        ports:
+        - containerPort: 80
+        volumeMounts:
+        - name: workdir
+          mountPath: /usr/share/nginx/html
+      initContainers:
+      - name: install
+        image: busybox:1.28
+        command:
+        - /bin/sh
+        - -c
+        - "echo version-2 > /work-dir/index.html"
+        volumeMounts:
+        - name: workdir
+          mountPath: "/work-dir"
+      volumes:
+      - name: workdir
+        emptyDir: {}
+```
+
+Observe that calling the ip exposed by the service the requests are load balanced across the two versions:
+```bash
+while sleep 0.1; do curl $(kubectl get svc my-app-svc -o jsonpath="{.spec.clusterIP}"); done
+version-1
+version-1
+version-1
+version-2
+version-2
+version-1
+```
+
+If the v2 is stable, scale it up to 4 replicas and shoutdown the v1:
+```
+kubectl scale --replicas=4 deploy my-app-v2
+kubectl delete deploy my-app-v1
+while sleep 0.1; do curl $(kubectl get svc my-app-svc -o jsonpath="{.spec.clusterIP}"); done
+version-2
+version-2
+version-2
+version-2
+version-2
+version-2
+```
+
+</p>
+</details>
+
 ## Jobs
 
 ### Create a job named pi with image perl that runs the command with arguments "perl -Mbignum=bpi -wle 'print bpi(2000)'"