How to integrate your charm to Traefik

Traefik provides ingress to other charmed applications. If a charm integrates with Traefik, it can delegate the responsibility of providing ingress to Traefik.

See Ingress-related relations for more details on the Traefik charm ingress-related relations.

Add ingress to your charm

Traefik owns two charm libraries to facilitate integrating with it over ingress and ingress_per_unit. At the time of writing, the most recent ingress version is v2. You can verify what the latest version for the libraries is by visiting the documentation pages on Charmhub:

• ingress

• ingress_per_unit

The following steps assume we want to use ingress. Using ingress_per_unit is very similar, but the difference is ingress_per_unit provides ingress for each unit of the charm. An important feature is that ingress_per_unit supports listening for ingress changes for all units of the charm, which is often useful for the leader unit to monitor the ingress status of the entire application. See the documentation page for more details.

Add ingress to your charm

First, fetch the latest ingress library:

charmcraft fetch-lib charms.traefik_k8s.v2.ingress

This will download lib/charms/traefik_k8s/v2/ingress.py. The simplest way to use the library is to instantiate the IngressPerAppRequirer object from your charm’s constructor. You can immediately pass to it the host and port of the server you want ingress (useful if they are static), or you can defer that decision to a later moment by using the IngressPerAppRequirer.provide_ingress_requirements API.

from charms.traefik_k8s.v2.ingress import IngressPerAppRequirer, IngressReadyEvent

... # your charm's __init__(self, ...):
        self.ingress = IngressPerAppRequirer(self, host="foo.bar", port=80)
        self.framework.observe(self.ingress.ready, self._on_ingress_ready)
        self.framework.observe(self.ingress.revoked, self._on_ingress_revoked)

    def _on_ingress_ready(self, event: IngressPerAppReadyEvent):
        self.unit.status = ops.ActiveStatus(f"I have ingress at {event.url}!")

    def _on_ingress_revoked(self, _):
        self.unit.status = ops.WaitingStatus(f"I have lost my ingress URL!")

    def _foo(self):
        self.ingress.provide_ingress_requirements(host="foo.com", port=42)

Once you have added the ingress library the charm would need to be re-packed with charmcraft pack.

IngressPerAppRequirer will take care of communicating over the ingress relation with traefik-k8s and notifying the charm whenever Traefik replies with an ingress URL or that URL is revoked for some reason (e.g. the cloud admin removed the relation).

Get the proxied endpoint exposed by Traefik

Deploy your charm alongside traefik-k8s and integrate them.

Use the show-proxied-endpoints action to get a list of the endpoints currently exposed by traefik, one for each application integrated over ingress and one for each unit related over ingress_per_unit.

juju run traefik/0 show-proxied-endpoints

These are the URLs at which your workloads are externally accessible.