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I'm attempting to create a cluster on Google Kubernetes Engine that runs nginx, RStudio server and two Shiny apps, following and adapting this guide.

I have 4 workloads that are all green in the UI, deployed via:

kubectl run nginx --image=nginx --port=80
kubectl run rstudio --image gcr.io/gcer-public/persistent-rstudio:latest --port 8787
kubectl run shiny1 --image gcr.io/gcer-public/shiny-googleauthrdemo:latest --port 3838
kubectl run shiny5 --image=flaviobarros/shiny-wordcloud --port=80

They were then all exposed as node ports via:

kubectl expose deployment nginx --target-port=80  --type=NodePort
kubectl expose deployment rstudio --target-port=8787  --type=NodePort
kubectl expose deployment shiny1 --target-port=3838  --type=NodePort
kubectl expose deployment shiny5 --target-port=80  --type=NodePort

..that are all green in the UI.

I then deployed this Ingress backend

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: r-ingress
spec:
  rules:
  - http:
      paths:
      - path: /
        backend:
          serviceName: nginx
          servicePort: 80
      - path: /rstudio/
        backend:
          serviceName: rstudio
          servicePort: 8787
      - path: /shiny1/
        backend:
          serviceName: shiny1
          servicePort: 3838
      - path: /shiny5/
        backend:
          serviceName: shiny5
          servicePort: 80

The result is that the nginx routing works great, I can see "Welcome to nginx" webpage from home, but the three other paths I get:

  • /rstudio/ - Input/output error
  • /shiny1/ - Page not found (the Shiny 404 page)
  • /shiny5/ - Page not found (the Shiny 404 page)

The RStudio and Shiny workloads both work when exposing via the single load balancer, mapped to 8787 and 3838 respectively.

Can anyone point to where I'm going wrong?

Qs:

  • Do the Dockerfiles need to be adapted so they all give a 200 status on port 80 when requesting "/"? Do I need to change the health checker? I tried changing the RStudio login page (that 302 to /auth-sign-in if you are not logged in) but no luck
  • Both RStudio and Shiny need websockets - does this affect this?
  • Does session affinity need to be on? I tried adding that with IP but same errors.
MarkeD
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  • This could help for RStudio Server (not heavily tested, actually): https://stackoverflow.com/questions/52303064/configuring-rstudio-server-service-for-nginx-ingress-in-gke/52364023#52364023 – Gabriele B Sep 17 '18 at 08:55
  • This is all sorted now for Shiny etc but ran into same issue you had with RStudio, so thank for link! I blogged my solution here http://code.markedmondson.me/r-on-kubernetes-serverless-shiny-r-apis-and-scheduled-scripts/ – MarkeD Sep 17 '18 at 14:26
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    I know your blog, it's an endless resource of inspiration and good stuff; i'm happy to help :) – Gabriele B Sep 17 '18 at 19:39
  • Thanks! I will look to update it with RStudio – MarkeD Sep 18 '18 at 07:48

2 Answers2

4

the most likely problem you have is that when you go with this ingress you attached your URI is different then with direct accesc ( /shiny1/ vs / ) so your app is lost and has no content for that uri.

With Nginx Ingress Controller you can use ingress.kubernetes.io/rewrite-target: / annotation to mitigate this and make sure that / is accessed even when there is a subfolder in the ingress path.

Radek 'Goblin' Pieczonka
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  • So if the Rstudio in the Docker was available from /rstudio/ and the Shiny app from /shiny1/ then it could work? Or do you have an example on how to rewrite the path? – MarkeD Jan 25 '18 at 22:34
  • the annotation I provided is that rewrite config, so either that or as you suggest, make your apps respond on these paths – Radek 'Goblin' Pieczonka Jan 26 '18 at 08:27
4

As Radek suggested, ingress.kubernetes.io/rewrite-target: / is required to re-write your requests. However, this is not currently supported by the GKE ingress controller and is the reason that you're receiving 404 responses.

Instead, on GKE, you must use an nginx ingress controller.

You will then be able to configure ingress for your rstudio and shiny images that obeys the rewrite rule:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: r-ingress
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - http:
      paths:
      - backend:
          serviceName: rstudio
          servicePort: 8787
        path: /rstudio/*
      - backend:
          serviceName: shiny1
          servicePort: 3838
        path: /shiny1/*
      - backend:
          serviceName: shiny5
          servicePort: 80
        path: /shiny5/*
Rhys Jackson
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  • Thanks Rhys! I tried the above and all goes well until trying to get an external IP - no matter how long I wait kubectl get ingress r-ingress isn't returning an IP. Did I miss something? – MarkeD Feb 23 '18 at 21:16
  • Oh do I need to install all those at the link? https://github.com/kubernetes/ingress-nginx/blob/master/deploy/README.md – MarkeD Feb 23 '18 at 21:19
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    That's correct. The GKE instructions will configure a Google Cloud Load Balancer that load balances traffic to a deployment named `nginx-ingress-controller`. This load balancer will create your external IP address. Inbound traffic on this IP that matches an ingress rule (like the one in my example) will be forwarded by the `nginx-ingress-controller` to the appropriate backend service. If no rules match, the traffic will be routed to the `default-http-backend` service which returns a 404 page. – Rhys Jackson Feb 26 '18 at 11:10
  • I eventually deployed nginx successfully through helm using this tutorial https://cloud.google.com/community/tutorials/nginx-ingress-gke – MarkeD Apr 25 '18 at 11:57
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    Attention it changed in version 0.22.0 of ingress-nginx. checkout example at https://github.com/kubernetes/ingress-nginx/blob/master/docs/examples/rewrite/README.md Now you have to work with captured groups to pass a subpath to the rewrite-target. – Matthias Wiedemann Jun 28 '19 at 12:32