KubernetesServicePatch Add support for creating a new K8s service (#90)

* add support for creating a new service

* fmt

* addressing comments

* pre-set service name if lb

* fmt

* linter reqs

* update docs

* refactor _remove_service

lib/charms/observability_libs/v1/kubernetes_service_patch.py

@@ -109,6 +109,26 @@ def __init__(self, *args):
     # ...
 ```
 
+Creating a new k8s lb service instead of patching the one created by juju
+Service name is optional. If not provided, it defaults to {app_name}-lb.
+If provided and equal to app_name, it also defaults to {app_name}-lb to prevent conflicts with the Juju default service.
+```python
+from charms.observability_libs.v1.kubernetes_service_patch import KubernetesServicePatch
+from lightkube.models.core_v1 import ServicePort
+
+class SomeCharm(CharmBase):
+  def __init__(self, *args):
+    # ...
+    port = ServicePort(int(self.config["charm-config-port"]), name=f"{self.app.name}")
+    self.service_patcher = KubernetesServicePatch(
+        self,
+        [port],
+        service_type="LoadBalancer",
+        service_name="application-lb"
+    )
+    # ...
+```
+
 Additionally, you may wish to use mocks in your charm's unit testing to ensure that the library
 does not try to make any API calls, or open any files during testing that are unlikely to be
 present, and could break your tests. The easiest way to do this is during your test `setUp`:
@@ -146,7 +166,7 @@ def setUp(self, *unused):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 9
+LIBPATCH = 10
 
 ServiceType = Literal["ClusterIP", "LoadBalancer"]
 
@@ -186,10 +206,15 @@ def __init__(
         """
         super().__init__(charm, "kubernetes-service-patch")
         self.charm = charm
-        self.service_name = service_name if service_name else self._app
+        self.service_name = service_name or self._app
+        # To avoid conflicts with the default Juju service, append "-lb" to the service name.
+        # The Juju application name is retained for the default service created by Juju.
+        if self.service_name == self._app and service_type == "LoadBalancer":
+            self.service_name = f"{self._app}-lb"
+        self.service_type = service_type
         self.service = self._service_object(
             ports,
-            service_name,
+            self.service_name,
             service_type,
             additional_labels,
             additional_selectors,
@@ -202,6 +227,7 @@ def __init__(
         self.framework.observe(charm.on.install, self._patch)
         self.framework.observe(charm.on.upgrade_charm, self._patch)
         self.framework.observe(charm.on.update_status, self._patch)
+        self.framework.observe(charm.on.stop, self._remove_service)
 
         # apply user defined events
         if refresh_event:
@@ -277,7 +303,10 @@ def _patch(self, _) -> None:
             if self._is_patched(client):
                 return
             if self.service_name != self._app:
-                self._delete_and_create_service(client)
+                if not self.service_type == "LoadBalancer":
+                    self._delete_and_create_service(client)
+                else:
+                    self._create_lb_service(client)
             client.patch(Service, self.service_name, self.service, patch_type=PatchType.MERGE)
         except ApiError as e:
             if e.status.code == 403:
@@ -294,6 +323,12 @@ def _delete_and_create_service(self, client: Client):
         client.delete(Service, self._app, namespace=self._namespace)
         client.create(service)
 
+    def _create_lb_service(self, client: Client):
+        try:
+            client.get(Service, self.service_name, namespace=self._namespace)
+        except ApiError:
+            client.create(self.service)
+
     def is_patched(self) -> bool:
         """Reports if the service patch has been applied.
 
@@ -321,6 +356,30 @@ def _is_patched(self, client: Client) -> bool:
         ]  # noqa: E501
         return expected_ports == fetched_ports
 
+    def _remove_service(self, _):
+        """Remove a Kubernetes service associated with this charm.
+
+        Specifically designed to delete the load balancer service created by the charm, since Juju only deletes the
+        default ClusterIP service and not custom services.
+
+        Returns:
+            None
+
+        Raises:
+            ApiError: for deletion errors, excluding when the service is not found (404 Not Found).
+        """
+        client = Client()  # pyright: ignore
+
+        try:
+            client.delete(Service, self.service_name, namespace=self._namespace)
+        except ApiError as e:
+            if e.status.code == 404:
+                # Service not found, so no action needed
+                pass
+            else:
+                # Re-raise for other statuses
+                raise
+
     @property
     def _app(self) -> str:
         """Name of the current Juju application.

tests/unit/test_kubernetes_service.py

@@ -250,7 +250,7 @@ def test_k8s_load_balancer_service(self):
             kind="Service",
             metadata=ObjectMeta(
                 namespace="test",
-                name="lb-test-charm",
+                name="lb-test-charm-lb",
                 labels={"app.kubernetes.io/name": "lb-test-charm"},
             ),
             spec=ServiceSpec(
@@ -405,14 +405,14 @@ def test_patch_k8s_service(self, client_patch):
         with self.assertLogs(MOD_PATH) as logs:
             self.harness.charm.service_patch._patch(None)
             msg = "Kubernetes service patch failed: `juju trust` this application."
-            self.assertIn(msg, ";".join(logs.output))
+            self.assertTrue(msg in ";".join(logs.output))
 
         client_patch.reset()
         client_patch.side_effect = _FakeApiError(500)
 
         with self.assertLogs(MOD_PATH) as logs:
             self.harness.charm.service_patch._patch(None)
-            self.assertIn("Kubernetes service patch failed: broken", ";".join(logs.output))
+            self.assertTrue("Kubernetes service patch failed: broken" in ";".join(logs.output))
 
     @patch(f"{MOD_PATH}.Client.get")
     @patch(f"{CL_PATH}._namespace", "test")
@@ -485,7 +485,7 @@ def test_is_patched_k8s_service_api_error_with_default_name(self, client):
         with self.assertLogs(MOD_PATH) as logs:
             with self.assertRaises(_FakeApiError):
                 self.harness.charm.service_patch.is_patched()
-            self.assertIn("Kubernetes service get failed: broken", ";".join(logs.output))
+            self.assertTrue("Kubernetes service get failed: broken" in ";".join(logs.output))
 
     @patch(f"{MOD_PATH}.ApiError", _FakeApiError)
     @patch(f"{CL_PATH}._namespace", "test")
@@ -499,4 +499,4 @@ def test_is_patched_k8s_service_api_error_not_404(self, client):
         with self.assertLogs(MOD_PATH) as logs:
             with self.assertRaises(_FakeApiError):
                 charm.custom_service_name_service_patch.is_patched()
-            self.assertIn("Kubernetes service get failed: broken", ";".join(logs.output))
+            self.assertTrue("Kubernetes service get failed: broken" in ";".join(logs.output))