app_container.md

From app to Kubernetes in 60 seconds

App

• A simple go app which just says hello

Dockerfile

• A multistage Dockerfile - first part builds source code into binary

• Second part takes binary from first part and creates an image

Building and running container locally

docker build -t app .

docker run -it --rm -p 8080:8080 app

Pushing image

$ docker tag app vishalbiyani/app
$ docker push vishalbiyani/app

Write pod spec

Every Kubernetes object is defined by a standard format

• The apiVersion and kind define the kind of object.
• Metadata has all the metadata about that object such as name, labels, annotations etc.
• Spec - is the core definition of the object itself and varies from object to object

apiVersion: v1
kind: <ObjectKind>
metadata:
  name: <Name>
  labels:
    <key>: <value>
spec:
  name: <Name>

So let's define a simple pod spec

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: vishalbiyani/app

Create Service spec

Similarly define a service spec:

apiVersion: v1
kind: Service
metadata:
  name: simpleapp
  labels:
    svc: myapp
spec:
  type: LoadBalancer
  ports:
  - port: 80
    targetPort: 8080
  selector:
    app: myapp

Apply specs

$ kubectl apply -f pod.yaml
$ kubectl apply -f service.yaml

Validate application works

$ kubectl get service