Generating a redirect with traefik ingress on k3s? - kubernetes

Question

I'm running prometheus and grafana under k3s, accessible (respectively) at http://monitoring.internal/prometheus and http://monitoring.internal/grafana. The grafana Ingress object, for example, looks like:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: grafana
annotations:
kubernetes.io/ingress.class: traefik
spec:
rules:
- host: monitoring.internal
http:
paths:
- path: /grafana
pathType: Prefix
backend:
service:
name: grafana
port:
number: 3000
This works fine, except that if you land at
http://monitoring.internal/, you get a 404 error. I would like
requests for http://monitoring.internal/ to redirect to
http://monitoring.internal/grafana. I could perhaps create another
service that runs something like darkhttpd ... --forward-all http://monitoring.internal/grafana, and create an Ingress object
that would map / to that service, but it seems like there ought to
be a way to do this with Traefik itself.
It looks like I'm running Traefik 2.4.8 locally:
$ kubectl -n kube-system exec -it deployment/traefik -- traefik version
Version: 2.4.8
Codename: livarot
Go version: go1.16.2
Built: 2021-03-23T15:48:39Z
OS/Arch: linux/amd64
I've found this documentation for 1.7 that suggests there is an annotation for exactly this purpose:
traefik.ingress.kubernetes.io/app-root: "/index.html": Redirects
all requests for / to the defined path.
But setting that on the grafana ingress object doesn't appear to have
any impact, and I haven't been able to find similar docs for 2.x
(I've looked around
here, for
example).
What's the right way to set up this sort of redirect?

Answer 1

Since I haven't been able to figure out traefik yet, I thought I'd post my solution here in case anyone else runs into the same situation. I am hoping someone comes along who knows The Right Way to to do this, and if I figure out I'll update this answer.
I added a new deployment that runs darkhttpd as a simple director:
apiVersion: apps/v1
kind: Deployment
metadata:
name: redirector
spec:
replicas: 1
template:
spec:
containers:
- name: redirector
image: docker.io/alpinelinux/darkhttpd
ports:
- containerPort: 8080
args:
- --forward-all
- http://monitoring.internal/grafana
A corresponding Service:
apiVersion: v1
kind: Service
metadata:
name: redirector
spec:
ports:
- port: 8080
protocol: TCP
targetPort: 8080
And the following Ingress object:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: redirector
annotations:
kubernetes.io/ingress.class: traefik
spec:
rules:
- host: monitoring.internal
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: redirector
port:
number: 8080
These are all deployed with kustomize, which takes care of
adding labels and selectors in the appropriate places. The
kustomization.yaml look like:
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- deployment.yaml
- ingress.yaml
- service.yaml
commonLabels:
component: redirector
With all this in place, requests to http://monitoring.internal/ hit the redirector pod.