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Kubernetes for Jobseekers by Gopalakrishnan Shivakumar;

Author:Gopalakrishnan, Shivakumar; [Gopalakrishnan, Shivakumar] , Date: March 26, 2023 ,Views: 120

Kubernetes for Jobseekers by Gopalakrishnan Shivakumar;

Author:Gopalakrishnan, Shivakumar; [Gopalakrishnan, Shivakumar]
Language: eng
Format: epub
Publisher: BPB Publications
Published: 2023-03-15T00:00:00+00:00


Higher availability with stable software is possible, if not for the pesky developers who want to achieve value to the customers in bug fixes and new features 😊.

Blue-green deployment

For a detailed look into blue-green deployment, see https://codefresh.io/blue-green-deployments-kubernetes/. A typical blue-green deployment diagram:

Figure 7.2: Blue-green deployments

Try it

Launch the blue version by running the following:

kubectl apply -f chap-7-blue-deployment-defn.yaml

The spec has a version label to denote whether it is blue or green:

Selector:

matchLabels:

app: frontend

version: blue

Launch the service frontend with a selector to match the version: blue:

kubectl apply -f chap-7-blue-svc-defn.yaml

spec:

selector:

app: frontend

version: blue

Verify that the app works:

$ kubectl get svc

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE

frontend NodePort 10.110.95.223 <none> 8080:32575/TCP 34h

$ curl localhost:32575

<!DOCTYPE html>

…

Let us intentionally launch a green version that we know will fail:

Kubectl apply -f chap-7-fail-green-deployment.yaml

The spec has the version label set to green:

Selector:

matchLabels:

app: frontend

version: green

As expected, the pods are not marked as READY:

Kubectl get pods

NAME READY STATUS RESTARTS AGE

nginx-blue-deployment-5778cb9488-4ssqj 1/1 Running 0 30s

nginx-blue-deployment-5778cb9488-68zwm 1/1 Running 0 30s

nginx-blue-deployment-5778cb9488-pf5tj 1/1 Running 0 30s

nginx-fail-green-deployment-db478459d-jfbqs 0/1 Running 0 6s

You can verify that the app still works by running curl localhost:<your service NodePort>. To ensure that the deployment is bad, let us ask the service to direct the traffic to the bad Pods:

Kubectl apply -f chap-7-green-svc-defn.yaml

Verify that the app does not work by running curl localhost:<your service NodePort>:

curl localhost:32575

curl: (52) Empty reply from server

You can see the benefit of the blue-green deployment. Even though we switched to the green deployment by mistake, we can quickly change it back to blue since we have not deleted the blue deployment:

Kubectl apply -f chap-7-blue-svc-defn.yaml



Download

Kubernetes for Jobseekers by Gopalakrishnan Shivakumar;.epub


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