Declarative Kubernetes with yaml

declarative-k8s.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment-name # The name of your Deployment
spec:
  replicas: 3 # The amount of replicated pods 
  selector:
    matchLabels: # specifies which pods the Deployment will target ("defines how the Deployment finds which Pods to manage")
      app: my-app
      environment: production
  template: # template defines how the pods will be created as part of the Deployment
    metadata:
      labels: # label the Pods
        app: my-app
        environment: production
    spec:
      containers: # array defining the containers within the Pod
        - name: my-app
          image: leonimurilo/node-app:1.0.11 # docker hub image
          ports:
            - containerPort: 3000 # you can tell kubernetes which port the container is listening to
          resources: # here you set the hardware resources your container will be able to use
            requests:
              memory: '256Mi'
              cpu: '0.5'
            limits:
              memory: '1024Mi'
              cpu: '2'
          env: # the environment variables set for the container
            - name: NODE_ENV
              value: "production" # this could even be dinamically inserted if you need
              # envs can also come from Kubernetes Secrets or reference Pod fields via fieldRef -> fieldPath

# The --- separates objects but you can also have separate files and use kubectl apply in an entire folder
---
apiVersion: v1
kind: Service
metadata:
  name: my-service-name
spec:
  type: NodePort # exposes the service on a static port on the node IP address
  ports: # defines which requests to a service port get forwarded to which ports on its Pods
  - NodePort: 32000 # access service via external port number (optional. if not set, the port will random be in the 30000-32767 range)
    port: 8080 # port exposed internally in cluster
    targetPort: 3000  # the port on which the app is running inside the container 
    protocol: TCP
    name: http
  selector:
    run: my-app