GoLang Tutorial - Building Docker image and deploying it to a Kubernetes cluster (minikube)

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Web application

In this post, we'll build a Docker image from the simple application we created earlier (Web Application Part 0 (Introduction)).

Here is the code:

This code is available : web-app-0.go

The application looks like this:

Dockerfile

Here is our Dockerfile:

FROM golang:alpine
RUN mkdir /app
COPY . /app
WORKDIR /app
RUN go build -o main . 
CMD ["/app/main"]

Let's build the image:

$ docker build -t go-app-img .
Sending build context to Docker daemon  7.304MB
Step 1/6 : FROM golang:alpine
 ---> b97a72b8e97d
Step 2/6 : RUN mkdir /app
 ---> Using cache
 ---> 493029660590
Step 3/6 : COPY . /app
 ---> e907c54b6b18
Step 4/6 : WORKDIR /app
 ---> Running in 130a4c80c611
Removing intermediate container 130a4c80c611
 ---> d7bb7a9a6db8
Step 5/6 : RUN go build -o main .
 ---> Running in 518fd62e940b
Removing intermediate container 518fd62e940b
 ---> 5ca1a1ef0e58
Step 6/6 : CMD ["/app/main"]
 ---> Running in 675128cd77bf
Removing intermediate container 675128cd77bf
 ---> 12af20a5db3f
Successfully built 12af20a5db3f
Successfully tagged go-app-img:latest

Run it:

$ docker run -d -p 3333:3000 --name go-app-container go-app-img
57a96e20d1766978d25685dd86384d696ba8d64433ef70ca9f41d64dcaefa1d9

Here we have indicated Docker to run a new container from our image (go-app-img) binding host port 3333 to container's internal port 3000 (-p 3333:3001), running the container in detached mode (-d) and giving a custom name to this container (-name go-app-container).

Go to the browser and navigate to localhost:3333:

Deploying to Kubernetes cluster

Let's deploy our app to Kubernetes cluster, well, to minikube.

Minikube

First, we need to start the minikube:

$ minikube start
😄  minikube v1.0.0 on darwin (amd64)
🤹  Downloading Kubernetes v1.14.0 images in the background ...
💡  Tip: Use 'minikube start -p ' to create a new cluster, or 'minikube delete' to delete this one.
🔄  Restarting existing virtualbox VM for "minikube" ...
⌛  Waiting for SSH access ...
📶  "minikube" IP address is 192.168.99.100
🐳  Configuring Docker as the container runtime ...
🐳  Version of container runtime is 18.06.2-ce
⌛  Waiting for image downloads to complete ...
✨  Preparing Kubernetes environment ...
🚜  Pulling images required by Kubernetes v1.14.0 ...
🔄  Relaunching Kubernetes v1.14.0 using kubeadm ... 
⌛  Waiting for pods: apiserver proxy etcd scheduler controller dns
📯  Updating kube-proxy configuration ...
🤔  Verifying component health ......
💗  kubectl is now configured to use "minikube"
🏄  Done! Thank you for using minikube!

Check the current status of the cluster:

$ kubectl get svc
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   12d

$ kubectl get pods
No resources found.

$ kubectl get deployments
No resources found.

Push the image to DockerHub

Let's push the image to DockerHub. To do that we may want to build the image specifying the repository:

$ docker build -t dockerbogo/go-app .
...
Successfully tagged dockerbogo/go-app:latest

$ docker push dockerbogo/go-app:latest
The push refers to repository [docker.io/dockerbogo/go-app]
...

Deploy to minikube cluster

Here is our deploy manifest file (deployment.yaml):

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-go-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: go-app
  template:
    metadata:
      labels:
        app: go-app
    spec:
      containers:
      - name: go-app-container
        image: dockerbogo/go-app
        resources:
          limits:
            memory: "128Mi"
            cpu: "500m"
        ports:
        - containerPort: 3000

Deploy:

$ kubectl create -f deployment.yaml
deployment.apps/my-go-app created

$ kubectl get deployments
NAME        READY     UP-TO-DATE   AVAILABLE   AGE
my-go-app   1/1       1            1           24s

$ kubectl get pods
NAME                         READY     STATUS    RESTARTS   AGE
my-go-app-5bb8767f6d-2pdtk   1/1       Running   0          43s

Exposing the go-app pod

Let's create a Service object that exposes the deployment:

$ kubectl expose deployment my-go-app --type=NodePort --name=go-app-svc --target-port=3000 
service/go-app-svc exposed

$ kubectl get svc
NAME         TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
go-app-svc   NodePort    10.111.127.140   <none>        3000:30652/TCP   81s
kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP          12d

$ minikube ip
192.168.99.100