fix: re-use existing connections on force refresh (#828)

Author: jackwotherspoon

google/cloud/sql/connector/connector.py

@@ -280,7 +280,7 @@ async def connect_async(
 
         except Exception:
             # with any exception, we attempt a force refresh, then throw the error
-            instance.force_refresh()
+            await instance.force_refresh()
             raise
 
     def __enter__(self) -> Any:

google/cloud/sql/connector/instance.py

@@ -255,16 +255,17 @@ def __init__(
         self._current = self._schedule_refresh(0)
         self._next = self._current
 
-    def force_refresh(self) -> None:
+    async def force_refresh(self) -> None:
         """
         Forces a new refresh attempt immediately to be used for future connection attempts.
         """
         # if next refresh is not already in progress, cancel it and schedule new one immediately
         if not self._refresh_in_progress.is_set():
             self._next.cancel()
             self._next = self._schedule_refresh(0)
-        # block all sequential connection attempts on the next refresh result
-        self._current = self._next
+        # block all sequential connection attempts on the next refresh result if current is invalid
+        if not await _is_valid(self._current):
+            self._current = self._next
 
     async def _perform_refresh(self) -> InstanceMetadata:
         """Retrieves instance metadata and ephemeral certificate from the

tests/unit/test_instance.py

@@ -194,7 +194,7 @@ async def test_force_refresh_cancels_pending_refresh(
     pending_refresh = instance._next
     assert instance._refresh_in_progress.is_set() is False
 
-    instance.force_refresh()
+    await instance.force_refresh()
 
     # pending_refresh has to be awaited for it to raised as cancelled
     with pytest.raises(asyncio.CancelledError):