Kubernetes Introduction

An introduction to Kubernetes, assuming you are running a local Kubernetes cluster.

Dashboard

Apply the dashboard:

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v1.10.1/src/deploy/recommended/kubernetes-dashboard.yaml

Start proxy:

kubectl proxy

Explore the API (download swagger.json from http://127.0.0.1/swagger.json):

docker run \
--name redoc-api-k8s \
-p 9001:80 \
--mount type=bind,src=`pwd`/swagger.json,dst=/usr/share/nginx/html/swagger.json \
-e SPEC_URL='swagger.json' \
redocly/redoc

Extract bearer token for web login:

kubectl -n kube-system describe secret $(kubectl -n kube-system get secret | grep dashboard | awk '{print $1}')

Log in with bearer token at http://localhost:8001/api/v1/namespaces/kube-system/services/https:kubernetes-dashboard:/proxy/.

Creating a deployment and service

In the top-right of the dashboard, click create and enter the following yaml:

apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
 name: whoami-deployment
spec:
 selector:
   matchLabels:
     app: whoami
 replicas: 3 # tells deployment to run 3 pods matching the template
 template:
   metadata:
     labels:
       app: whoami
   spec:
     containers:
     - name: whoami
       image: jwilder/whoami:latest
       ports:
       - containerPort: 8000

This will create a replication set with 3 pods maintained. To expose the pods as a load balanced externally available service, create the following:

apiVersion: v1
kind: Service
metadata:
 name: whoami-service
spec:
 selector:
   app: whoami
 type: LoadBalancer
 ports:
 - protocol: TCP
   port: 8002
   targetPort: 8000

Verify load balancing by running multiple instance of:

curl -s "http://127.0.0.1:8002/?[1-10]"