Introduction

This is sample nodejs app which exposes 2 end-points:

1. / - Returns Hello
2. /version - increments and returns count everytime this api is hit/refreshed

Instructions

1. clone repo

   git clone https://github.com/tprakash17/nodejs-sample-app-kubernetes.git
   cd nodejs-sample-app-kubernetes/node_app
   

2. Build docker image

   sudo docker build -t nodejs-v1 .
   

3. Verify app locally by running container

   docker run -d --name <SOMENAME> -p 8080:3000 nodejs-v1:latest
   

Note: nodejs-v1:latest image has been pushed to dockerhub as well and its publically available. (docker pull tarun/nodejs-v1)

4 Access in your local browser

http://localhost:8080

http://localhost:8080/version

Deploy app in kubernetes

create namespace and the deployment

root@Blr-Tarunp:~# kubectl create ns nodejs
root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl create -f nodejs-initial-deploy.yaml
deployment "node-deployment" created

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl create -f nodejs-svc-nodeport.yaml
service "nodeapp-svc" created

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl get all,ing -n nodejs
NAME                                 READY     STATUS        RESTARTS   AGE
po/node-deployment-97f45c487-jphkt   1/1       Running       0          1h
po/node-deployment-97f45c487-rpch4   1/1       Running       0          1h

NAME              CLUSTER-IP    EXTERNAL-IP   PORT(S)        AGE
svc/nodeapp-svc   10.43.80.18   <nodes>       80:30787/TCP   1h

NAME                     DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deploy/node-deployment   2         2         2            2           1h

NAME                           DESIRED   CURRENT   READY     AGE
rs/node-deployment-97f45c487   2         2         2         1h

Describe svc

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl describe svc/nodeapp-svc -n nodejs
Name:                   nodeapp-svc
Namespace:              nodejs
Labels:                 <none>
Annotations:            <none>
Selector:               app=nodeapp,color=blue,env=dev
Type:                   NodePort
IP:                     10.43.80.18
Port:                   http    80/TCP
NodePort:               http    30787/TCP
Endpoints:              10.42.142.245:3000,10.42.252.214:3000
Session Affinity:       None
Events:                 <none>

You can access the application by http://NODEIP:SERVICE-PORT or http://NODEIP:SERVICE-PORT/version (in my case it was 30787)

Horizontal scaling

$ kubectl autoscale deployment node-deployment --cpu-percent=40 --min=2 --max=10 -n nodejs

Scaler status

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl get hpa -n nodejs
NAME                  REFERENCE                    TARGETS    MINPODS   MAXPODS   REPLICAS   AGE
hpa/node-deployment   Deployment/node-deployment   0% / 30%   2         10        2          36s

Increase load

$ kubectl run -i --tty load-generator --image=busybox /bin/sh -n nodejs

Hit enter for command prompt

# while true; do wget -q -O- http://10.43.80.18; done

Note: Change the clusterIP it may be different when you deploy.

Watch scaler

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# watch kubectl get hpa -n nodejs
Every 2.0s: kubectl get hpa -n nodejs                                                                                                           Thu Sep 13 18:50:29 2018

NAME              REFERENCE                    TARGETS     MINPODS   MAXPODS   REPLICAS   AGE
node-deployment   Deployment/node-deployment   34% / 30%   2         10        4          14m

Now you can deployment has scaled to 4 copies automatically as load increased more than 30 %

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl get deploy -n nodejs
NAME              DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
load-generator    1         1         1            1           12m
node-deployment   4         4         4            4           1h

Now, delete the load generator.

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl delete deploy/load-generator -n nodejs
deployment "load-generator" deleted

verify that load has started coming down

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# watch kubectl get hpa -n nodejs
Every 2.0s: kubectl get hpa -n nodejs                                                                                                           Thu Sep 13 18:55:35 2018

NAME              REFERENCE                    TARGETS     MINPODS   MAXPODS   REPLICAS   AGE
node-deployment   Deployment/node-deployment   11% / 30%   2         10        5          19m

Rolling update

Go to nodejs-sample-app-kubernetes/kubernetes DIR run the script to do rolling update. Its always good to scale the app before doing rolling-upgrade to avoid performance degradation.

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes# ./rolling-update.sh
deployment "node-deployment" scaled
deployment "node-deployment" image updated

Blue green deployment

1. Deploy new version of your app with updated label
2. Change selector at svc level to match new label

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes# ./blue-green-update.sh
deployment "node-green-deployment" created
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
service "nodeapp-svc" configured

Clean UP

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl delete -f .
deployment "node-green-deployment" deleted
deployment "node-deployment" deleted
service "nodeapp-svc" deleted

root@Blr-Tarunp:~/nodejs-sample-app-kubernetes/kubernetes/artifacts# kubectl delete hpa node-deployment -n nodejs