Nginx

HeadLess service

For headless Services that do not define selectors, the endpoints controller does not create Endpoints records. However, the DNS system will create entries This will help application to do discovery of active pods

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx

Ordinal Index

Ordinal index starts from 0 to N-1 where N is the number of replicas in spec

Start/Stop order

For a StatefulSet with N replicas, when Pods are being deployed, they are created sequentially, in order from {0..N-1}

Nginx StatefulSet

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: "nginx"
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: k8s.gcr.io/nginx-slim:0.8
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi
      storageClassName: iscsi-targetd-vg-targetd

Basics

https://kubernetes.io/docs/tutorials/stateful-application/basic-stateful-set/