Kubernetes: Mapping a Service to a Deployment with YAML files

Question

I’m new to Kubernetes and learning about Deployments, Services, and Ingress as part of a CKAD video course. I created a YAML file for a Deployment, and a separate YAML file for a Service, and I’d like to map or hook up the Service with the Deployment. The container is a simple Nginx image, and I would like to be able to access the the Nginx server from the internal cluster IP address to begin with.

The deployment:

user@k8s-box:~/ch8$ cat ch8_deploy.yml 
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  creationTimestamp: null
  labels:
    app: ch8app
  name: ch8app-nginx
 spec:
  replicas: 5
  selector:
    matchLabels:
      app: ch8app
  strategy: 
    rollingUpdate:
      maxUnavailable: 2
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: ch8app
    spec:
      containers:
      - image: nginx:latest
        name: nginx
        resources: {}
 status: {}

The ClusterIP service:

user@k8s-box:~/ch8$ cat ch8_svc.yml
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: null
  labels:
    app: ch8app
  name: ch8svc   
spec:
  ports:
  - name: "tcp80"
    port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: ch8app-nginx  
  type: ClusterIP
status:
  loadBalancer: {}

Then I load the files:

kubectl create -f ch8_deploy.yml
kubectl create -f ch8_svc.yml

When I try to access port 80 with curl from the cluster internal IP address, I’m not able to connect. What am I missing in the above that is causing the mismatch? If I run the below, I’m able to connect successfully:

kubectl create -f ch8_deploy.yml
kubectl expose deploy ch8app-nginx —-port=80

While the above works, it’s not something like the YAML file that I could commit to a git repo for reproducing the environment.

Answer 1

In the service you have selector app: ch8app-nginx, but in the deployment you have labels app: ch8app. They don't match.