02-05-02 Kubernetes Deployment and Service

Create a deployment

Before starting, take a look at the YAML definition of the deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: dockercoins
spec:
  selector:
    matchLabels:
      app: dockercoins
  template:
    metadata:
      labels:
        app: dockercoins
    spec:
      containers:
      - name: rng
        image: rotcaus/dockercoins_rng:v1
        imagePullPolicy: Always
      - name: hasher
        image: rotcaus/dockercoins_hasher:v1
        imagePullPolicy: Always
      - name: webui
        image: rotcaus/dockercoins_webui:v1
        imagePullPolicy: Always
        ports:
        - containerPort: 80
      - name: worker
        image: rotcaus/dockercoins_worker:v1
        imagePullPolicy: Always
      - name: redis
        image: redis

There are a few noteworthy parts here:

• metadata: data to help identify uniquely an object (name, uid)
• spec: describes desired state for the object
  • spec.template is the template container spec (image, volumes to mount, and ports to expose etc)
• labels: key/value pairs used to organise and filter objects by labels. These can be added when creating the object or later. See kubectl get pods --show-labels.

Apply this deployment with the kubectl apply command:

kubectl apply -f deployment.yml

Now that the deployment is created, start looking at the events happening in the cluster:

kubectl get events --watch

Look for a new pod by running kubectl get pod. Once you have found it,

• describe the pod with kubectl describe pod [pod-name]
• show the application logs of each container in the pod with kubectl logs [pod-name]. This command will ask to specify which container you want to inspect (e.g: kubectl logs [pod-name] rng)