stateful set stuff

statefulset.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: httpbin-statefulset
spec:
  serviceName: httpbin
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
  template:
    metadata:
      labels:
        app: httpbin
        selector: httpbin
    spec:
      containers:
        - image: docker.io/kong/httpbin
          imagePullPolicy: IfNotPresent
          name: httpbin
          # Same as found in Dockerfile's CMD but using an unprivileged port
          command:
          - gunicorn
          - -b
          - 0.0.0.0:8080
          - httpbin:app
          - -k
          - gevent
          env:
          # Tells pipenv to use a writable directory instead of $HOME
          - name: WORKON_HOME
            value: /tmp
          ports:
          - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
spec:
  clusterIP: None
  selector:
    app: httpbin
  ports:
    - port: 80
      targetPort: 8080

Assuming you've scaled up the set, you can run nslookup (from another pod) against the service name:

$ nslookup httpbin.default.svc.cluster.local
Server:         10.96.0.10
Address:        10.96.0.10:53


Name:   httpbin.default.svc.cluster.local
Address: 10.244.0.12
Name:   httpbin.default.svc.cluster.local
Address: 10.244.0.13
Name:   httpbin.default.svc.cluster.local
Address: 10.244.0.14

Note the 3 IP address at the end correspond to the pods' IP addresses. Then, if you do nslookup against any of the instances:

 nslookup httpbin-statefulset-0.httpbin.default.svc.cluster.local
Server:         10.96.0.10
Address:        10.96.0.10:53

Name:   httpbin-statefulset-0.httpbin.default.svc.cluster.local
Address: 10.244.0.12

And doing curl httpbin-statefulset-0.httpbin.default.svc.cluster.local:8080/headers will send a response to the pod 0.