Rollout (Rolling Update)¶

In this step we will deploy the same application with several different versions and we will “switch” between them.
For learning purposes we will play a little with the CLI.

01. Create namespace¶

As completed in the previous lab, create the desired namespace [codewizard]:

$ kubectl create namespace codewizard
namespace/codewizard created

In order to set this is as the default namespace, please refer to set default namespace.

02. Create the desired deployment¶

We will use the save-config flag

save-config
If true, the configuration of current object will be saved in its annotation.
Otherwise, the annotation will be unchanged.
This flag is useful when you want to perform kubectl apply on this object in the future.
Let’s run the following:
```
$ kubectl create deployment -n codewizard nginx --image=nginx:1.17 --save-config
```
Note that in case we already have this deployed, we will get an error message.

03. Expose nginx as a service¶

$ kubectl expose deployment -n codewizard nginx --port 80 --type NodePort
service/nginx exposed

Again, note that in case we already have this service we will get an error message as well.

04. Verify that the pods and the service are running¶

$ kubectl get all -n codewizard

# The output should be similar to this
NAME                        READY      STATUS    RESTARTS   AGE
pod/nginx-db749865c-lmgtv   1/1        Running   0          66s

NAME                        TYPE       CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE
service/nginx               NodePort   10.102.79.9   <none>        80:31204/TCP   30s

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx   1/1     1            1           66s

NAME                              DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-db749865c   1         1         1       66s

05. Change the number of replicas to 3¶

$ kubectl scale deployment -n codewizard nginx --replicas=3
deployment.apps/nginx scaled

06. Verify that now we have 3 replicas¶

$ kubectl get pods -n codewizard
NAME                    READY   STATUS    RESTARTS   AGE
nginx-db749865c-f5mkt   1/1     Running   0          86s
nginx-db749865c-jgcvb   1/1     Running   0          86s
nginx-db749865c-lmgtv   1/1     Running   0          4m44s

07. Test the deployment¶

# !!! Get the Ip & port for this service
$ kubectl get services -n codewizard -o wide 

# Write down the port number
NAME    TYPE       CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE    SELECTOR
nginx   NodePort   10.102.79.9   <none>        80:31204/TCP   7m7s   app=nginx

# Get the cluster IP and port
$ kubectl cluster-info  
Kubernetes control plane is running at https://192.168.49.2:8443

# Using the above <host>:<port> test the nginx
# -I is for getting the headers
$ curl -sI <host>:<port>

# The response should display the nginx version
example: curl -sI 192.168.49.2:31204

HTTP/1.1 200 OK
Server: nginx/1.17.10 <------------ This is the pod version
Date: Fri, 15 Jan 2021 20:13:48 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 14 Apr 2020 14:19:26 GMT
Connection: keep-alive
ETag: "5e95c66e-264"
Accept-Ranges: bytes
...

08. Deploy another version of nginx¶

# Deploy another version of nginx (1.16)
$ kubectl set image deployment -n codewizard nginx nginx=nginx:1.16 --record
deployment.apps/nginx image updated

# Check to verify that the new version deployed - same as in previous step
$ curl -sI <host>:<port>

# The response should display the new version
HTTP/1.1 200 OK
Server: nginx/1.16.1 <------------ This is the pod version (new version)
Date: Fri, 15 Jan 2021 20:16:11 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 13 Aug 2019 10:05:00 GMT
Connection: keep-alive
ETag: "5d528b4c-264"
Accept-Ranges: bytes

09. Investigate rollout history:¶

The rollout history command print out all the saved records:

$ kubectl rollout history deployment nginx -n codewizard
deployment.apps/nginx
REVISION  CHANGE-CAUSE
1         <none>
2         kubectl set image deployment nginx nginx=nginx:1.16 --record=true
3         kubectl set image deployment nginx nginx=nginx:1.15 --record=true

10. Let’s see what was changed during the previous updates:¶

Print out the rollout changes:

# replace the X with 1 or 2 or any number revision id
$ kubectl rollout history deployment nginx -n codewizard --revision=<X>  # replace here
deployment.apps/nginx with revision #1
Pod Template:
  Labels:       app=nginx
        pod-template-hash=db749865c
  Containers:
   nginx:
    Image:      nginx:1.17
    Port:       <none>
    Host Port:  <none>
    Environment:        <none>
    Mounts:     <none>
  Volumes:      <none>

11. Undo the version upgrade by rolling back and restoring previous version¶

# Check the current nginx version
$ curl -sI <host>:<port>

# Undo the last deployment
$ kubectl rollout undo deployment nginx
deployment.apps/nginx rolled back

# Verify that we have the previous version
$ curl -sI <host>:<port>

12. Rolling Restart¶

If we deploy using imagePullPolicy: always set in the YAML file, we can use rollout restart to force K8S to grab the latest image.
This is the fastest restart method these days

# Force pods restart
kubectl rollout restart deployment [deployment_name]