protocol detection for keycloak

Bug Report

Seems like protocol detection for keycloak-cluster discovery is not supported:

Adding skip-port for clustering traffic fixes the issue:

  keycloak:
    podAnnotations:
      config.linkerd.io/skip-inbound-ports: "7600" # skip keycloak cluster discovery
      config.linkerd.io/skip-outbound-ports: "7600"

What is the issue?

When deploying keycloak in a clustered manner, linkerd seems to break keycloaks clustering traffic

How can it be reproduced?

Deploy keycloak with replicas >1 (we use the helm chart), when you log into the service, an error will occur and you are logged out. If you are fast you will see some 401 in the browser before you are redirected to the loginscreen. This happens because the other node dont know that you are logged inn.

Environment

• Kubernetes Version: 1.15.7
• Cluster Environment: AKS
• Host OS:
• Linkerd version: 2.6.1

No source file or test is identified in the report. Reproduce the failure with a Keycloak deployment using more than one replica on Kubernetes, then trace Linkerd's protocol detection for the cluster-discovery traffic; done means clustered login works without skipping port 7600.