I don't get keycloak. Anyone who has experience with it, please help.

We have what I would think is a common setup: a kubernetes cluster with a Spring boot api-gateway and keycloak as oauth2-provider.

The api-gateway needs an issuer-uri to keycloak for endpoint discovery, i.e. to configure a bunch of endpoints to keykloak for different purposes.

The two main purposes are: 1. to redirect the user to keycloak (must be an url reachable from outside the cluster, i.e. ingress) 2. to authenticate tokens directly with keycloak from within the cluster.

Keycloak can be configured to set some of these discovery endpoints to different values. Specifically it makes a separation between backfacing (system calls in cluster) and frontfacing (user call from browser) urls All seems good.

However, when using this setup, each time spring security authenticates a token against keycloak it says the "issuer" is invalid. This is because the issuer is the host on which the token was generated. This host was the one in the url which the user was redirected to i.e. the ingress.

It feels like there is no way around this except running keycloak outside the Kubernetes cluster, but surely there must be a way to run keycloak in the same cluster. What else is the purpose of keycloak having the concept of back- and frontfacing urls?