Merge pull request #177 from ashutoshbhakare/patch-4

Blue Green Deployment
collabnix · Dec 13, 2023 · 5463a53 · 5463a53
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diff --git a/bluegreen/README.md b/bluegreen/README.md
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+# What is Blue-Green Deployment ? 
+Blue-Green deployment is basically an application deployment method using which we can easily update one version – named as BLUE while the another version named as GREEN will keep serving the request once done we can switch back to BLUE if required . It has great advantage for real production scenarios, no downtime is required and guess what we can easily switch to older version whenever required .
+
+# How Blue-Green Deployment works ? 
+This can be easily archived using labels and selectors; we will mostly use kubectl patch command as below, Note: we can even do this manually by editing service.
+```
+kubectl patch service  SERVICENAME -p '{"spec":{"selector":{"KEY": "VALUE"}}}'
+``` 
+In this example we will create two pods with the httpd image and will change the “It Works “message to “It Works – Blue Deployment” and “It Works – Green Deployment” for second Pod. We will also create a service which will map to blue first and once the update is done we will patch it to green. 
+
+# Creating a Pod with Labels
+```
+git clone https://github.com/collabnix/kubelabs
+cd kubelabs/bluegreen
+```
+```
+$ kubectl apply -f blue.yml 
+pod/bluepod created
+```
+
+```
+$ kubectl get pods --show-labels
+NAME        READY   STATUS    RESTARTS   AGE   LABELS
+bluepod         1/1     Running   0          25m   app=blue
+
+$ kubectl apply -f green.yml 
+pod/greenpod created
+```
+
+```
+$ kubectl get pods --show-labels
+NAME        READY   STATUS    RESTARTS   AGE   LABELS
+bluepod         1/1     Running   0       25m   app=blue
+greenpod        1/1     Running   0       28m   app=green
+```
+
+```
+svc.yml
+apiVersion: v1
+kind: Service
+metadata:
+  creationTimestamp: null
+  labels:
+    app: testing
+  name: myapp
+spec:
+  ports:
+  - port: 80
+    protocol: TCP
+    targetPort: 80
+  selector:
+    app: blue
+status:
+  loadBalancer: {}
+```
+In the above service yaml file we are mapping to our blue pod  via selectors. 
+
+Just for understanding purpose we are changind, the default landing page of our httpd application
+```
+kubectl exec -it bluepod bash
+kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
+root@bluepod:/usr/local/apache2# echo "Hello from Blue-Pod" >> htdocs/index.html 
+exit
+```
+```
+kubectl exec -it greenpod bash
+kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
+root@greenpod:/usr/local/apache2# echo "Hello from Green-Pod" >> htdocs/index.html 
+exit
+```
+We can verify if both the pods are having the updated output or not. 
+```
+kubectl get pods -o wide
+NAME            READY   STATUS    RESTARTS   AGE     IP            NODE     NOMINATED NODE   READINESS GATES
+bluepod         1/1     Running   0          5m38s   192.168.1.7   node01   <none>           <none>
+greenpod        1/1     Running   0          4m48s   192.168.1.8   node01   <none>           <none>
+
+controlplane $ curl 192.168.1.7
+<html><body><h1>It works!</h1></body></html>
+Hello from Blue-Pod
+
+controlplane $ curl 192.168.1.8
+<html><body><h1>It works!</h1></body></html>
+Hello from Green-Pod
+controlplane $ 
+```
+Not let see how it works with service IP 
+controlplane $ kubectl get svc
+NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
+kubernetes   ClusterIP   10.96.0.1      <none>        443/TCP   2d5h
+myapp        ClusterIP   10.100.35.84   <none>        80/TCP    2s
+```
+curl 10.100.35.84
+<html><body><h1>It works!</h1></body></html>
+Hello from Blue-Pod
+```
+Lets try to switch to our green deployment by changing the service mapping using below command, if we try to curl the service IP it should take us to the green pod. 
+```
+kubectl patch service myapp -p '{"spec":{"selector":{"app": "green"}}}'
+
+controlplane $ curl 10.100.35.84
+<html><body><h1>It works!</h1></body></html>
+Hello from Green-Pod
+```
+
+In this way, we can conclude work on blue green deployment works
+
+# Contributors
+[Ashutosh S.Bhakare](https://www.linkedin.com/in/abhakare/).
+
+
diff --git a/bluegreen/blue.yml b/bluegreen/blue.yml
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+apiVersion: v1
+kind: Pod
+metadata:
+    name: bluepod
+    labels: 
+        app: blue
+spec:
+    containers:
+    - name: webpage
+      image: docker.io/httpd 
diff --git a/bluegreen/green.yml b/bluegreen/green.yml
@@ -0,0 +1,10 @@
+apiVersion: v1
+kind: Pod
+metadata:
+    name: greenpod
+    labels: 
+        app: green
+spec:
+    containers:
+    - name: webpage
+      image: docker.io/httpd 
diff --git a/bluegreen/svc.yml b/bluegreen/svc.yml
@@ -0,0 +1,16 @@
+apiVersion: v1
+kind: Service
+metadata:
+  creationTimestamp: null
+  labels:
+    app: testing
+  name: myapp
+spec:
+  ports:
+  - port: 80
+    protocol: TCP
+    targetPort: 80
+  selector:
+    app: blue
+status:
+  loadBalancer: {}