How to integrate with external agent charms

We consider any agent charm to be external when they don’t have layer 3 connectivity with the jenkins-k8s charm. To integrate with those agent charms, we’ll leverage the jenkins-k8s charm’s agent-discovery-ingress integration.

The agent-discovery-ingress integration can be used with any charm that supports the :ingress interface. One example is the traefik-k8s charm.

juju integrate jenkins-k8s:agent-discovery-ingress traefik-k8s:ingress

Agents considered external have to be integrated using a cross-model integration. To integrate with such agent, simply integrate with the ingress provider charm as mentioned above and then integrate with the agent charm’s offer endpoint.

juju integrate jenkins-k8s:agent-discovery-ingress traefik-k8s:ingress
juju integrate jenkins-k8s:agent <offer-endpoint>

Networking considerations

The charm assumes that:

1. There are connectivity between the juju controller of the jenkins-k8s charm and the juju controller of the agent charm trying to connect with the jenkins-k8s charm.
2. The agent can resolve the ingress hostname provided by the jenkins-k8s charm and the resulting IP address is reachable, and there are firewall rules in place to allow HTTP traffic.
3. In case a reverse proxy is present, it is also expected that the HTTP connection coming from the agent charm is allowed to be upgraded into a Websocket connection. The reverse proxy should also be configured with a suitable idle timeout for websocket connections to avoid intermittent agent disconnection.