Applicable versions

All Longhorn versions with Traefik 2.x as ingress controller.

Note that, the CORS problem would not happen with Traefik 1.x as ingress controller.

Symptoms

The Longhorn GUI frontend API requests sometimes failed to reach longhorn-manager backend.

Reason

The API requests would change the protocol between HTTPS/WSS, and the change would lead to a CORS problem.

Solution

The Traefik 2.x ingress controller does not set the WebSocket headers.

1. Adds the following middleware to the route for the Longhorn frontend service.

   apiVersion: traefik.containo.us/v1alpha1
   kind: Middleware
   metadata:
     name: svc-longhorn-headers
     namespace: longhorn-system
   spec:
     headers:
       customRequestHeaders:
         X-Forwarded-Proto: "https"
   

2. Updates the ingress to use the middleware rule.

   apiVersion: networking.k8s.io/v1beta1
   kind: Ingress
   metadata:
     name: longhorn-ingress
     namespace: longhorn-system
     annotations:
       traefik.ingress.kubernetes.io/router.entrypoints: websecure
       traefik.ingress.kubernetes.io/router.tls: "true"       
       traefik.ingress.kubernetes.io/router.middlewares: longhorn-system-svc-longhorn-headers@kubernetescrd
   spec:
     rules:
     - http:
         paths:
         - path: /
           backend:
             serviceName: longhorn-frontend
             servicePort: 80
   

Related information

• Longhorn issue comment: https://github.com/longhorn/longhorn/issues/1442#issuecomment-639761799