nginx-ingress-integrator has no charm-overrides file: solver connects mutually-exclusive ingress/nginx-route relations and omits required service-hostname config

Summary

nginx-ingress-integrator has no static/charm-overrides/nginx-ingress-integrator.yaml file. As a result the bundle solver treats ingress and nginx-route (both provides) as independently optional/required with no relationship between them, and never sets the service-hostname config the charm requires when ingress is connected. This produces bundles the charm cannot actually run.

Reproduction

Test plan: integration/nginx-ingress-integrator:ingress/ingress/traefik-k8s:upstream-ingress (SQT-1178 traefik-k8s QA, revision 378, latest/stable).

./scripts/run-tests.sh \
  --target-cloud "local-k8s" \
  --target-charm "traefik-k8s" --target-endpoint "upstream-ingress" \
  --target-channel "latest/stable" --target-revision "378" \
  --target-platform "kubernetes" --target-application "target" \
  --neighbor-charm "nginx-ingress-integrator" --neighbor-endpoint "ingress" \
  --neighbor-platform "kubernetes" --neighbor-application "neighbor" \
  --current-state "no_bundle" \
  --charm-overrides "./static/charm-overrides/"

(Requires the platform-detection fix in #956 / PR for nginx-ingress-integrator to be treated as kubernetes-only first; otherwise the run fails earlier with a platform mismatch.)

Observed failure 1: both mutually-exclusive endpoints connected

With no override, the solver additionally pulled in wordpress-k8s (needs nginx-route) alongside traefik-k8s (needs ingress), connecting neighbor to both endpoints simultaneously. juju status showed:

neighbor/0*  blocked   idle   ...  Both nginx-route and ingress relations found, please remove either one.

Confirmed in nginx-ingress-integrator-operator source, src/charm.py::_check_precondition:

if nginx_route_relation is not None and ingress_relation is not None:
    raise InvalidIngressError(
        "Both nginx-route and ingress relations found, please remove either one."
    )

Also _update_ingress sets WaitingStatus("waiting for relation") forever if neither is connected (src/charm.py) - so exactly one of the two must be connected, never zero, never both.

Observed failure 2: missing service-hostname config

After constraining to exactly one endpoint, neighbor still blocked when only ingress was connected:

neighbor/0*  blocked   idle   ...  service-hostname is not set for the ingress relation, configure it using `juju config`

Confirmed in src/ingress_definition.py::IngressDefinitionEssence.service_hostname:

service_hostname = cast(str, self._get_config_or_relation_data("service-hostname", ""))
if not service_hostname:
    if self.is_ingress_relation:
        raise InvalidIngressError(
            "service-hostname is not set for the ingress relation, "
            "configure it using `juju config`"
        )

For the ingress (ingress-per-app) interface there is no relation-data fallback for hostname (unlike nginx-route, whose requirer passes it via relation data), so service-hostname config must be set whenever ingress is connected.

Fix

Add static/charm-overrides/nginx-ingress-integrator.yaml:

• provides.ingress / provides.nginx-route: both optional: true, constrained by len(endpoint[ingress]) + len(endpoint[nginx-route]) == 1 (exactly one).
• requires.certificates: optional: true (_get_tls_relation() returns early without it).
• configs.service-hostname: ['nginx-ingress-integrator.test', null] with constraint bool(endpoint[ingress]) => set(config[service-hostname]).

Validated: solver now produces a single-endpoint bundle with service-hostname set; deployed end-to-end on a k8s model (traefik-k8s rev378 latest/stable + nginx-ingress-integrator), both units reach active.

Fixed on branch SQT-1178/nginx-ingress-integrator-exclusive-relations (stacked on the platform-detection fix, since this charm was previously misdetected as machine-only).

Related: SQT-1178, depends on #956 (nginx-ingress-integrator platform detection).

Start with scripts/run-tests.sh and the reproduction command, then inspect the existing files under static/charm-overrides/ for the expected YAML structure. Add static/charm-overrides/nginx-ingress-integrator.yaml with the stated endpoint, certificates, and service-hostname constraints. Done means the solver selects exactly one ingress endpoint, sets service-hostname when ingress is used, and the k8s deployment reaches active.