refactor: Cache create_schema_registry_client and rename to get_...

This is just foundation for the next commit.

edx_event_bus_kafka/config.py

@@ -3,9 +3,12 @@
 """
 
 import warnings
+from functools import lru_cache
 from typing import Optional
 
 from django.conf import settings
+from django.dispatch import receiver
+from django.test.signals import setting_changed
 
 # See https://github.com/openedx/event-bus-kafka/blob/main/docs/decisions/0005-optional-import-of-confluent-kafka.rst
 try:
@@ -16,10 +19,13 @@
 
 
 # return type (Optional[SchemaRegistryClient]) removed from signature to avoid error on import
-def create_schema_registry_client():
+@lru_cache
+def get_schema_registry_client():
     """
     Create a schema registry client from common settings.
 
+    This is cached for convenience.
+
     Returns
         None if confluent_kafka library is not available or the settings are invalid.
         SchemaRegistryClient if it is.
@@ -69,3 +75,9 @@ def load_common_settings() -> Optional[dict]:
         })
 
     return base_settings
+
+
+@receiver(setting_changed)
+def _reset_state(sender, **kwargs):  # pylint: disable=unused-argument
+    """Reset caches during testing when settings change."""
+    get_schema_registry_client.cache_clear()

edx_event_bus_kafka/consumer/event_consumer.py

@@ -13,7 +13,7 @@
 from openedx_events.learning.signals import SESSION_LOGIN_COMPLETED
 from openedx_events.tooling import OpenEdxPublicSignal
 
-from edx_event_bus_kafka.config import create_schema_registry_client, load_common_settings
+from edx_event_bus_kafka.config import get_schema_registry_client, load_common_settings
 
 logger = logging.getLogger(__name__)
 
@@ -68,7 +68,7 @@ def _create_consumer(self):
             DeserializingConsumer if it is.
         """
 
-        schema_registry_client = create_schema_registry_client()
+        schema_registry_client = get_schema_registry_client()
 
         # TODO (EventBus):
         # 1. Reevaluate if all consumers should listen for the earliest unprocessed offset (auto.offset.reset)

edx_event_bus_kafka/publishing/event_producer.py

@@ -14,7 +14,7 @@
 from openedx_events.event_bus.avro.serializer import AvroSignalSerializer
 from openedx_events.tooling import OpenEdxPublicSignal
 
-from edx_event_bus_kafka.config import create_schema_registry_client, load_common_settings
+from edx_event_bus_kafka.config import get_schema_registry_client, load_common_settings
 
 logger = logging.getLogger(__name__)
 
@@ -161,7 +161,7 @@ def get_producer_for_signal(signal: OpenEdxPublicSignal, event_key_field: str):
         logger.warning('Library confluent-kafka not available. Cannot create event producer.')
         return None
 
-    schema_registry_client = create_schema_registry_client()
+    schema_registry_client = get_schema_registry_client()
     if schema_registry_client is None:
         return None
 

edx_event_bus_kafka/tests/test_config.py

@@ -17,11 +17,11 @@
 
 class TestSchemaRegistryClient(TestCase):
     def test_unconfigured(self):
-        assert config.create_schema_registry_client() is None
+        assert config.get_schema_registry_client() is None
 
     def test_configured(self):
         with override_settings(EVENT_BUS_KAFKA_SCHEMA_REGISTRY_URL='http://localhost:12345'):
-            assert isinstance(config.create_schema_registry_client(), SchemaRegistryClient)
+            assert isinstance(config.get_schema_registry_client(), SchemaRegistryClient)
 
 
 class TestCommonSettings(TestCase):