fix: run credential refresh of connectors in threads (#512)

Author: rhatgadkar-goog

google/cloud/alloydbconnector/async_connector.py

@@ -216,12 +216,12 @@ async def connect(
         logger.debug(f"['{instance_uri}']: Connecting to {ip_address}:5433")
 
         # callable to be used for auto IAM authn
-        def get_authentication_token() -> str:
+        async def get_authentication_token() -> str:
             """Get OAuth2 access token to be used for IAM database authentication"""
             # refresh credentials if expired
             if not self._db_credentials.valid:
                 request = google.auth.transport.requests.Request()
-                self._db_credentials.refresh(request)
+                await asyncio.to_thread(self._db_credentials.refresh, request)
             return self._db_credentials.token
 
         # if enable_iam_auth is set, use auth token as database password

tests/unit/test_async_connector.py

@@ -240,7 +240,7 @@ async def test_connect_iam_authn(credentials: FakeCredentials) -> None:
 
         async def custom_connect(*_: Any, **kwargs: Any) -> bool:
             passwd = kwargs.pop("password")
-            passwd()
+            await passwd()
 
         # patch db connection creation
         with patch(
@@ -272,7 +272,7 @@ async def test_connect_db_credentials_iam_authn(credentials: FakeCredentials) ->
 
         async def custom_connect(*_: Any, **kwargs: Any) -> bool:
             passwd = kwargs.pop("password")
-            passwd()
+            await passwd()
 
         # patch db connection creation
         with patch(