GoLang App --> Docker --> k8s

A "hello world" app to demonstrate simple web server. Contains a Dockerfile that is based off of instructions here.

We also will push the dockerized GoLang app to a Kubernetes cluster using an included yaml file.

Docker Pull and Run

Docker version can be run with the commands

$ docker pull andrebriggs/goserver
$ docker run --rm -p 8080:8080  andrebriggs/goserver

Test that the app is running locally by running

$ curl http://localhost:8080

You should see

Congratulations! Version 1.0 of your application is running on Kubernetes.

Docker Build and Push

If you want to roll your own image use the following commands below, otherwise skip to the next section.

$ docker run --rm -v "$PWD":/go/src/github.com/andrebriggs/goserver -w /go/src/github.com/andrebriggs/goserver iron/go:dev go build -o bin/myapp
$ docker build -t andrebriggs/goserver:latest .

Note that in the first line we build "myapp" outside of the Dockerfile. The dependency of go at iron/go:dev isn't a part of the final image so we save space. Be sure to replace andrebriggs with your own DockerHub account name

FInally I pushed the image to DockerHub

$ docker push andrebriggs/goserver

Kubernetes Setup

Once pushed I can declaratively set a Kubernetes environment (assuming one is created) to use this resource

$ kubectl create -f k8s

To verify the creation with can ask kubectl to describe the service with the command

$ kubectl describe svc mywebapp

The result will be similar to this

Name:                     mywebapp
Namespace:                default
Labels:                   app=mywebapp
Annotations:              kubectl.kubernetes.io/last-applied-configuration:
                            {"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"app":"mywebapp"},"name":"mywebapp","namespace":"default"},"spe...
Selector:                 app=mywebapp
Type:                     LoadBalancer
IP:                       10.0.210.108
LoadBalancer Ingress:     137.116.69.143
Port:                     http  8080/TCP
TargetPort:               8080/TCP
NodePort:                 http  31855/TCP
Endpoints:                10.200.0.69:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:
  Type    Reason                Age    From                Message
  ----    ------                ----   ----                -------
  Normal  EnsuringLoadBalancer  6m2s   service-controller  Ensuring load balancer
  Normal  EnsuredLoadBalancer   5m14s  service-controller  Ensured load balancer

Make a note of the external IP address (LoadBalancer Ingress) exposed by the service. Read more about this here.

You should be able to access the web app

$ curl http://(LoadBalancer Ingress IP):8080
Congratulations! Version 1.0 of your application is running on Kubernetes.

Update the Docker image

Suppose you make changes to server.go file to update hardcoded version to 1.2 and want to push new changes the Docker image tag as a v1.2. Do the following commands

$ docker run --rm -v "$PWD":/go/src/github.com/andrebriggs/goserver -w /go/src/github.com/andrebriggs/goserver iron/go:dev go build -o bin/myapp
$ docker build -t andrebriggs/goserver:v1.2 .
$ docker tag andrebriggs/goserver:latest andrebriggs/goserver:v1.2
$ docker push andrebriggs/goserver:v1.2

Rollout a new deployment

Edit the manifest YAML file to alter the .spec.containers.image to be andrebriggs/goserver:v1.2

    ...
    spec:
      containers:
      - name: mywebapp
        image: andrebriggs/goserver:v1.2
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8080

Also edit the .spec.replicas value to be 10

Save then run

$ kubectl apply -f k8s --record

Then immediately run the following to check the status of the deploy

kubectl rollout status deployment mywebapp-v1

Once done try hitting the endpoint again with curl and see your changes.

Congratulations! Version 1.2 of your application is running on Kubernetes.

Helm Chart

There is a helm chart for this repo in the mywebapp directory. It is used in a Fabrikate definition here.

Kubernetes tear down

Run the commands

$ kubectl delete services mywebapp
$ kubectl delete deployment mywebapp