IngressPerAppRequirer: retry when IP is not available

lib/charms/traefik_k8s/v2/ingress.py

@@ -84,7 +84,7 @@ def _on_ingress_revoked(self, event: IngressPerAppRevokedEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 14
+LIBPATCH = 15
 
 PYDEPS = ["pydantic"]
 
@@ -338,6 +338,10 @@ class DataValidationError(IngressError):
     """Raised when data validation fails on IPU relation data."""
 
 
+class IpNotAvailableError(IngressError):
+    """Raised when retrieving ip information from juju failed."""
+
+
 class _IngressPerAppBase(Object):
     """Base class for IngressPerUnit interface classes."""
 
@@ -710,7 +714,12 @@ def __init__(
 
     def _handle_relation(self, event):
         # created, joined or changed: if we have auto data: publish it
-        self._publish_auto_data()
+        try:
+            self._publish_auto_data()
+        except IpNotAvailableError as e:
+            log.error(e)
+            event.defer()
+            return
         if self.is_ready():
             # Avoid spurious events, emit only when there is a NEW URL available
             new_url = (
@@ -728,7 +737,12 @@ def _handle_relation_broken(self, event):
 
     def _handle_upgrade_or_leader(self, event):
         """On upgrade/leadership change: ensure we publish the data we have."""
-        self._publish_auto_data()
+        try:
+            self._publish_auto_data()
+        except IpNotAvailableError as e:
+            log.error(e)
+            event.defer()
+            return
 
     def is_ready(self):
         """The Requirer is ready if the Provider has sent valid data."""
@@ -794,7 +808,7 @@ def _publish_unit_data(
             ):
                 ip = str(bind_address)
             else:
-                log.error("failed to retrieve ip information from juju")
+                raise IpNotAvailableError("failed to retrieve ip information from juju")
 
         unit_databag = relation.data[self.unit]
         try:

tests/scenario/test_ingress_per_app.py

@@ -15,7 +15,7 @@
     IngressRequirerUnitData,
 )
 from ops import CharmBase, Framework
-from scenario import Context, Model, Mount, Relation, State
+from scenario import Context, Model, Mount, Network, Relation, State
 
 from tests.scenario._utils import create_ingress_relation
 from tests.scenario.conftest import MOCK_LB_ADDRESS
@@ -188,6 +188,23 @@ def test_ingress_per_app_requirer_with_auto_data(host, ip, port, model, evt_name
         }
 
 
+@pytest.mark.parametrize("evt_name", ("joined", "changed"))
+@pytest.mark.parametrize("leader", (True, False))
+def test_ingress_per_app_requirer_retry_without_ip(model, evt_name, leader):
+    ipa = Relation("ingress")
+    state = State(
+        model=model,
+        leader=leader,
+        relations=[ipa],
+        networks={"ingress": Network(bind_addresses=[], egress_subnets=[], ingress_addresses=[])},
+    )
+    requirer_ctx = get_requirer_ctx("10.0.0.1", None, 80)
+    state_out = requirer_ctx.run(getattr(ipa, evt_name + "_event"), state)
+
+    assert len(state_out.deferred) == 1
+    assert state_out.deferred[0].name == f"ingress_relation_{evt_name}"
+
+
 def test_ingress_per_app_cleanup_on_remove(model, traefik_ctx, traefik_container):
     """Check that config file is removed when a relation is."""
     ipa = create_ingress_relation()

tests/unit/test_lib_per_app_requires.py

@@ -12,6 +12,7 @@
     IngressPerAppReadyEvent,
     IngressPerAppRequirer,
     IngressPerAppRevokedEvent,
+    IpNotAvailableError,
 )
 from ops.charm import CharmBase
 from ops.testing import Harness
@@ -157,12 +158,5 @@ def test_ipa_events_juju_binding_failure(self):
             self.harness.begin_with_initial_hooks()
             self.rel_id = self.harness.add_relation("ingress", "traefik-app")
             self.harness.add_relation_unit(self.rel_id, "traefik-app/0")
-            self.harness.charm.ipa.provide_ingress_requirements(port=80)
-
-            self.assertEqual(
-                # None is default so it gets omitted
-                self.harness.get_relation_data(self.rel_id, "ipa-requirer/0").get(
-                    "ip", "<OMITTED>"
-                ),
-                "<OMITTED>",
-            )
+            with self.assertRaises(IpNotAvailableError):
+                self.harness.charm.ipa.provide_ingress_requirements(port=80)