Javascript content (DT, Leaflet) does not load on Google Cloud Kubernetes

[markusdumke]

I am facing some issues that Javscript-related content like DT datatables or leaflet maps sometimes do not load in my shiny app deployed with Kubernetes on Google Cloud.

In the browser console I see 404 ressource not found error codes.

The error seems to be stochastic as sometimes everything is correctly displayed. It may be linked with the Load Balancer I think. Does anyone has any ideas how to fix this?

Example app is here

[markusdumke]

So, what I think is causing this is missing session affinity. A request is send to a different pod, where the ressources are then not found resulting in the 404 errors. Can anybody confirm that I need session affinity for shiny apps?

What I read is that session affinity won't work with services of type NodePort unless using the nginx ingress type in Kubernetes. So I tried to configure an nginx ingress, but I am stuck, what annotations I have to set.

This is the config I tried:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: shiny
  labels:
    app: shiny
spec:
  replicas: 1
  selector:
    matchLabels:
      app: shiny
  template:
    metadata:
      labels:
        app: shiny
    spec:
      containers:
      - name: shiny
        image: rocker/shiny:3.6.1
        ports:
        - containerPort: 3838
---
kind: Service
apiVersion: v1
metadata:
  name: shiny
spec:
  selector:
    app: shiny
  type: NodePort
  ports:
  - protocol: TCP
    port: 80
    targetPort: 3838
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: shiny-ingress
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/affinity: "cookie"
    nginx.ingress.kubernetes.io/session-cookie-expires: "86400"
    nginx.ingress.kubernetes.io/session-cookie-max-age: "86400"
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
    nginx.ingress.kubernetes.io/affinity-mode: persistent
    nginx.ingress.kubernetes.io/session-cookie-hash: sha1
spec:
  rules:
  - host: www.example.com
    http:
      paths:
      - backend:
          serviceName: shiny-service
          servicePort: 80

I have read I'm losing my mind with shiny + Kubernetes which seems to be a similar issue. Not sure, how to get my app running, so any help is appreciated!