Traefik as Reverse Proxy to backend services

Traefik Traefik v2
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1

Hello experts,

I am relative new to Traefik Proxy here. We are setting up a k3s test environment and wants to utilize Traefik Proxy for Ingress implementation. Our use case are below:

  1. We have multiple tomcat services (which deployed the same web application package, e.g. sampleApp); so normally we can access the service by (http://[host]:[port]/sampleApp), I have retried to define the ingress to forward different path to different tomcat services, e.g.
kind: Ingress
apiVersion: networking.k8s.io/v1
metadata:
  name: sampleApps
  namespace: default
  annotations:
    traefik.ingress.kubernetes.io/router.entrypoints: web

spec:
  rules:
    - http:
        paths:
          - path: /sampleApp1
            pathType: Prefix
            backend:
              service:
                name: sampleApp1
                port:
                  number: 8080
          - path: /sampleApp2
            pathType: Prefix
            backend:
              service:
                name: sampleApp2
                port:
                  number: 8080

Problem is that when I access URL http://..../sampleApp1, it returns 404 page not found. This is because Traefik proxy simpley forward the same URL request to the backend, and as tomcat is expecting a sub-path like sampleApp only. Is there any solution (e.g. middleware) can be used, that for end-user, we are still requesting to /sampleApp1, but while traefik proxy communicate with relative backend services it's sending /sampleApp instead?

Thanks and Regards,
Mike

2

Hello @mike818148 and thanks for your interest in Traefik,

I think you can use the replacepathregexp to replace the /sampleAppN path by /sampleApp (this could also work by using the stripprefix and addprefix middlewares).

Hope this helps!

3

Hello @kevinpollet

Thanks a lot for your reply. I did tried replace path and stripprefix middleward. However, this also replace the URL on user's browser. e.g.

  1. Request: /sampleApp1
  2. Replace the /sampleApp1 to /sampleApp
  3. Then I observe that browser starts to request the sub-sequent pages also with /sampleApp, e.g. /sampleApp/home.jsf which will leads to 404 page not found again.

So I am wondering the replace path (or stripprefix) will also reflect the changes on the sub-sequent requests on user's browser?

Thanks and Regards,
Mike

4

So I am wondering the replace path (or stripprefix) will also reflect the changes on the sub-sequent requests on user's browser?

That is because the proxied application does not know that it is exposed under a subpath. This means that the page rendered by the application should contain links with URLs containing /sampleApp1 not /sampleApp. This is something usually configurable. Maybe the app can also use the header sent by Traefik to obtain the exposed subpath and render the links correctly.

5

Hello Kevin,

Thanks for the hint. This is achievable for self-developed applications. But while we want to integrate with other applications this is not so feasible. For example, mainly dashboard container service (e.g. kubernetes dashboard, traefik dashboard, docker-registry dashboard...) they mostly just use / as the Base URL path. Which comes to similiar situation, that if I configured a path in the Ingress, and it will be recognized as a sub-path in the proxied applications. And we hit 404 again.

I believe there should be a better solution to play Traefik as Reverse Proxy instead of simply forwarding? As changing the behaviour in every application is not a perfect solution when we scale up.

Thanks and Regards,
Mike

6

I believe there should be a better solution to play Traefik as Reverse Proxy instead of simply forwarding? As changing the behaviour in every application is not a perfect solution when we scale up.

That is why it is better to do Host routing (see Traefik Routers Documentation - Traefik and/or Ingress | Kubernetes) instead of path routing. Thus, by using subdomains it is not required to configure subpath in applications (i.e. kubernetes.dashboard.foo.com, traefik.dashboard.foo.com).

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