flask-socketio in kubernetes, ingress and multiple replicas

Question

i'm running a flask-socketio behind an ingress. here's the config:

socketio = SocketIO(app, message_queue='redis://redis-server.domain:6379')

in the dockerfile, it runs like so:

CMD ["gunicorn", "-k", "geventwebsocket.gunicorn.workers.GeventWebSocketWorker", "-w", "4", "--bind", "0.0.0.0:2731", "app:app"]

and the ingress is configured like this:

nginx.ingress.kubernetes.io/affinity: "cookie"
nginx.ingress.kubernetes.io/enable-ssl-passthrough: "true"
nginx.ingress.kubernetes.io/session-cookie-name: "route"

i also tried replacing "cookie" with "ip_hash"

whenever i add a second replica pod, it starts returning error 400, as if it contacts the pods interchangeably, and not sticking to the same server, thus breaking the socket.

any ideas?

Answer 1

Ideally, it should have worked but try this .spec.sessionAffinity

Set it to service

.spec.sessionAffinity value will be ClientIP

Service to POD sticky session

kind: Service
apiVersion: v1
metadata:
  name: test-service
spec:
  selector:
    app: test-app
  ports:
  - name: http
    protocol: TCP
    port: 80
    targetPort: 80
  sessionAffinity: ClientIP