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A Practical Guide to Kubernetes

Deploying the First Release

Explore the process of deploying the first release of a Kubernetes application within namespaces. Understand how to modify deployment definitions dynamically using command-line tools to specify image tags and verify your deployment through HTTP requests, gaining practical experience with Kubernetes workflows.

We'll cover the following...

Looking into the definition

We’ll start by deploying the go-demo-2 application and use it to explore namespaces. The file is shown below:

YAML
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: go-demo-2
  annotations:
    kubernetes.io/ingress.class: "nginx"
    ingress.kubernetes.io/ssl-redirect: "false"
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
  rules:
  - host: go-demo-2.com
    http:
      paths:
      - path: /demo
        pathType: ImplementationSpecific
        backend:
          service:
            name: go-demo-2-api
            port:
              number: 8080
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: go-demo-2-db
spec:
  selector:
    matchLabels:
      type: db
      service: go-demo-2
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        type: db
        service: go-demo-2
        vendor: MongoLabs
    spec:
      containers:
      - name: db
        image: mongo:3.3
---
apiVersion: v1
kind: Service
metadata:
  name: go-demo-2-db
spec:
  ports:
  - port: 27017
  selector:
    type: db
    service: go-demo-2
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: go-demo-2-api
spec:
  replicas: 3
  selector:
    matchLabels:
      type: api
      service: go-demo-2
  template:
    metadata:
      labels:
        type: api
        service: go-demo-2
        language: go
    spec:
      containers:
      - name: api
        image: vfarcic/go-demo-2
        env:
        - name: DB
          value: go-demo-2-db
        readinessProbe:
          httpGet:
            path: /demo/hello
            port: 8080
          periodSeconds: 1
        livenessProbe:
          httpGet:
            path: /demo/hello
            port: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: go-demo-2-api
spec:
  ports:
  - port: 8080
  selector:
    type: api
    service: go-demo-2

The definition is the same as the one we used before, so we’ll skip the explanation of the YAML file. Instead, we’ll jump right away into the deployment.

Altering the definition

Unlike previous cases, we’ll deploy a specific tag of the application. If this would be a Docker Swarm stack, we’d define the tag of the vfarcic/go-demo-2 image as an environment variable ...