Authelia can act as an Open ID Connect identity provider. This allows
it to provide authentication/authorization for other applications
besides those inside the Kubernetes cluster using it for Ingress
authentication.
To start with, we'll configure an OIDC client for Jenkins.
I am not entirely sure why, but it seems like the Kubelet *always*
misses the first check in the readiness probe. This causes a full
60-second delay before the Authelia pod is marked as "ready," even
though it was actually ready within a second of the container starting.
To avoid this very long delay, during which Authelia is unreachable,
even though it is working fine, we can add a startup probe with a much
shorter check interval. The kubelet will not start readiness probes
until the startup probe returns successfully, so it won't miss the first
one any more.
Authelia is a general authentication provider that works (primarily)
by integrating with *nginx* using its subrequest mechanism. It works
great with Kubernetes/*ingress-nginx* to provide authentication for
services running in the cluster, especially those that do not provide
their own authentication system.
Authelia needs a database to store session data. It supports various
engines, but since we're only running a very small instance with no real
need for HA, SQLite on a Longhorn persistent volume is sufficient.
Configuration is done mostly through a YAML document, although some
secret values are stored in separate files, which are pointed to by
environment variables.
Dustin