Make use of a reset_pod_reflector fixture when needed

kubespawner/spawner.py

@@ -55,6 +55,11 @@ class PodReflector(ResourceReflector):
 
     kind = "pods"
 
+    # The default component label can be over-ridden by specifying the component_label property
+    labels = {
+        'component': 'singleuser-server',
+    }
+
     @property
     def pods(self):
         """
@@ -113,25 +118,24 @@ class KubeSpawner(Spawner):
     spawned by a user will have its own KubeSpawner instance.
     """
 
-    # Reflectors are stored in class variable for performance reasons.
-    # If every pod will start its own reflector, Kubelet will not be happy
-    # with attaching 20k event watchers
-    reflectors = {}
+    # Reflectors keeping track of the k8s api-server's state for various k8s
+    # resources are singletons as that state can be tracked and shared by all
+    # KubeSpawner objects.
+    reflectors = {
+        "pods": None,
+        "events": None,
+    }
 
     # Characters as defined by safe for DNS
     # Note: '-' is not in safe_chars, as it is being used as escape character
     safe_chars = set(string.ascii_lowercase + string.digits)
 
-    def get_reflector_key(self, kind: str) -> tuple:
-        namespace = None if self.enable_user_namespaces else self.namespace
-        return (kind, self.component_label, namespace)
-
     @property
     def pod_reflector(self):
         """
         A convenience alias to the class variable reflectors['pods'].
         """
-        return self.__class__.reflectors.get(self.get_reflector_key('pods'))
+        return self.__class__.reflectors['pods']
 
     @property
     def event_reflector(self):
@@ -140,9 +144,7 @@ def event_reflector(self):
         spawner instance has events_enabled.
         """
         if self.events_enabled:
-            return self.__class__.reflectors.get(self.get_reflector_key('events'))
-
-        return None
+            return self.__class__.reflectors['events']
 
     def __init__(self, *args, **kwargs):
         _mock = kwargs.pop('_mock', False)
@@ -2378,9 +2380,9 @@ async def progress(self):
 
     def _start_reflector(
         self,
-        kind: str,
-        reflector_class: ResourceReflector,
-        replace: bool = False,
+        kind=None,
+        reflector_class=ResourceReflector,
+        replace=False,
         **kwargs,
     ):
         """Start a shared reflector on the KubeSpawner class
@@ -2395,7 +2397,8 @@ def _start_reflector(
         If replace=True, a running pod reflector will be stopped
         and a new one started (for recovering from possible errors).
         """
-        key = self.get_reflector_key(kind)
+        key = kind
+        ReflectorClass = reflector_class
 
         def on_reflector_failure():
             self.log.critical(
@@ -2407,7 +2410,7 @@ def on_reflector_failure():
         previous_reflector = self.__class__.reflectors.get(key)
 
         if replace or not previous_reflector:
-            self.__class__.reflectors[key] = reflector_class(
+            self.__class__.reflectors[key] = ReflectorClass(
                 parent=self,
                 namespace=self.namespace,
                 on_failure=on_reflector_failure,
@@ -2457,10 +2460,11 @@ def _start_watching_pods(self, replace=False):
         If replace=True, a running pod reflector will be stopped
         and a new one started (for recovering from possible errors).
         """
+        pod_reflector_class = PodReflector
+        pod_reflector_class.labels.update({"component": self.component_label})
         return self._start_reflector(
-            kind="pods",
-            reflector_class=PodReflector,
-            labels={"component": self.component_label},
+            "pods",
+            PodReflector,
             omit_namespace=self.enable_user_namespaces,
             replace=replace,
         )
@@ -2637,7 +2641,6 @@ async def _make_create_resource_request(self, kind, manifest):
         else:
             return True
 
-    @_await_pod_reflector
     async def _start(self):
         """Start the user's pod"""
 

tests/conftest.py

@@ -31,6 +31,7 @@
 from kubernetes_asyncio.watch import Watch
 from traitlets.config import Config
 
+from kubespawner import KubeSpawner
 from kubespawner.clients import shared_client
 
 here = os.path.abspath(os.path.dirname(__file__))
@@ -623,3 +624,22 @@ async def exec_python(kube_client, kube_ns):
     pod = await create_resource(kube_client, kube_ns, "pod", pod_manifest)
 
     yield partial(_exec_python_in_pod, kube_client, kube_ns, pod_name)
+
+
+@pytest.fixture(scope="function")
+def reset_pod_reflector():
+    """
+    Resets the class state KubeSpawner.reflectors["pods"] before and after the
+    test function executes. This enables us to start fresh if a test needs to
+    test configuration influencing our singleton pod reflector.
+    """
+
+    def _reset_pod_reflector():
+        pods_reflector = KubeSpawner.reflectors["pods"]
+        KubeSpawner.reflectors["pods"] = None
+        if pods_reflector:
+            asyncio.ensure_future(pods_reflector.stop())
+
+    _reset_pod_reflector()
+    yield
+    _reset_pod_reflector()

tests/test_spawner.py

@@ -211,6 +211,7 @@ async def test_spawn_component_label(
     kube_client,
     config,
     hub,
+    reset_pod_reflector,
 ):
     spawner = KubeSpawner(
         hub=hub,
@@ -339,6 +340,7 @@ async def test_spawn_services_enabled(
     kube_client,
     hub,
     config,
+    reset_pod_reflector,
 ):
     spawner = KubeSpawner(
         config=config,