Add warning if ingress is not established

src/charm.py

@@ -17,6 +17,7 @@
 from ops.main import main
 
 from components.config_generation import GenerateEnvoyConfig, GenerateEnvoyConfigInputs
+from components.ingress import IngressRelationWarnIfMissing, IngressRelationWarnIfMissingInputs
 from components.pebble import EnvoyPebbleService, EnvoyPebbleServiceInputs
 
 ENVOY_CONFIG_FILE_PATH = "/envoy/envoy.json"
@@ -68,6 +69,17 @@ def __init__(self, *args):
             depends_on=[self.leadership_gate],
         )
 
+        self.ingress_relation_warn_if_missing = self.charm_reconciler.add(
+            component=IngressRelationWarnIfMissing(
+                charm=self,
+                name="ingress-relation-warn-if-missing",
+                inputs_getter=lambda: IngressRelationWarnIfMissingInputs(
+                    interface=self.ingress_relation.component.get_interface()
+                ),
+            ),
+            depends_on=[self.ingress_relation],
+        )
+
         self.envoy_config_generator = self.charm_reconciler.add(
             GenerateEnvoyConfig(
                 charm=self,

src/components/ingress.py

@@ -0,0 +1,39 @@
+import dataclasses
+import logging
+from typing import Optional
+
+from charmed_kubeflow_chisme.components import Component
+from ops import ActiveStatus, BlockedStatus, StatusBase
+
+
+@dataclasses.dataclass
+class IngressRelationWarnIfMissingInputs:
+    """Defines the required inputs for IngressRelationWarnIfMissing."""
+
+    interface: Optional[dict]
+
+
+class IngressRelationWarnIfMissing(Component):
+    """Component that logs a warning if we have no Ingress relation established."""
+
+    def __init__(self, *args, **kwargs):
+        """Component that logs a warning if we have no Ingress relation established."""
+        super().__init__(*args, **kwargs)
+        # Attach a logger.  Use this instead of the global one to make mocking easier
+        self.logger = logging.getLogger(__name__)
+
+    def get_status(self) -> StatusBase:
+        """Always Active unless it cannot get inputs."""
+        try:
+            inputs = self._inputs_getter()
+            if not inputs.interface:
+                self.logger.warning(
+                    "No ingress relation established.  To be used by KFP in Charmed Kubeflow, this"
+                    " charm requires an Ingress relation."
+                )
+                return ActiveStatus("Active but no ingress relation established")
+
+            return ActiveStatus()
+        except Exception as e:
+            self.logger.error(f"Error getting inputs for IngressRelationWarnIfMissing: {e}")
+            return BlockedStatus("Error getting inputs.  See logs")

tests/unit/test_charm.py

@@ -81,6 +81,41 @@ def test_with_ingress_relation(self, harness):
 
         assert harness.charm.ingress_relation.status == ActiveStatus()
 
+    def test_warning_if_ingress_missing(self, harness, mocker):
+        """Test that we emit a warning if we do not have an ingress established."""
+        harness.set_leader(True)
+        setup_grpc_relation(harness, "grpc-one", "8080")
+
+        harness.begin()
+
+        # Mock the ingress warning logger so we can check if it was called
+        mock_logger = mocker.MagicMock()
+        harness.charm.ingress_relation_warn_if_missing.component.logger = mock_logger
+
+        # Do something that will reconcile the charm
+        harness.charm.on.config_changed.emit()
+
+        # Assert that we've logged the missing ingress relation
+        assert "No ingress relation established" in mock_logger.warning.call_args[0][0]
+
+    def test_no_warning_if_ingress_is_established(self, harness, mocker):
+        """Test that we emit a warning if we do not have an ingress established."""
+        harness.set_leader(True)
+        setup_grpc_relation(harness, "grpc-one", "8080")
+        setup_ingress_relation(harness)
+
+        harness.begin()
+
+        # Mock the ingress warning logger so we can check if it was called
+        mock_logger = mocker.MagicMock()
+        harness.charm.ingress_relation_warn_if_missing.component.logger = mock_logger
+
+        # Do something that will reconcile the charm
+        harness.charm.on.config_changed.emit()
+
+        # Assert that we haven't logged anything
+        assert mock_logger.warning.call_args is None
+
     def test_envoy_config_generator(self, harness):
         """Test the envoy_config_generator Component is active when prerequisites are ready."""
         harness.set_leader(True)