chore: improve connector.close (#985)

google/cloud/sql/connector/connector.py

@@ -308,15 +308,17 @@ async def __aexit__(
 
     def close(self) -> None:
         """Close Connector by stopping tasks and releasing resources."""
-        close_future = asyncio.run_coroutine_threadsafe(
-            self.close_async(), loop=self._loop
-        )
-        # Will attempt to safely shut down tasks for 5s
-        close_future.result(timeout=5)
+        if self._loop.is_running():
+            close_future = asyncio.run_coroutine_threadsafe(
+                self.close_async(), loop=self._loop
+            )
+            # Will attempt to safely shut down tasks for 5s
+            close_future.result(timeout=5)
         # if background thread exists for Connector, clean it up
         if self._thread:
-            # stop event loop running in background thread
-            self._loop.call_soon_threadsafe(self._loop.stop)
+            if self._loop.is_running():
+                # stop event loop running in background thread
+                self._loop.call_soon_threadsafe(self._loop.stop)
             # wait for thread to finish closing (i.e. loop to stop)
             self._thread.join()
 
@@ -327,6 +329,12 @@ async def close_async(self) -> None:
             *[instance.close() for instance in self._instances.values()]
         )
 
+    def __del__(self) -> None:
+        """Close Connector as part of garbage collection"""
+        # only want to call destructor when used for sync connections
+        if self._thread:
+            self.close()
+
 
 async def create_async_connector(
     ip_type: IPTypes = IPTypes.PUBLIC,

tests/unit/test_connector.py

@@ -137,3 +137,16 @@ def test_Connector_close_kills_thread() -> None:
     connector.close()
     # check that connector thread is no longer running
     assert connector._thread.is_alive() is False
+
+
+def test_Connector_close_called_multiple_times() -> None:
+    """Test that Connector.close can be called multiple times."""
+    # open and close Connector object
+    connector = Connector()
+    # verify background thread exists
+    assert connector._thread
+    connector.close()
+    # check that connector thread is no longer running
+    assert connector._thread.is_alive() is False
+    # call connector.close a second time
+    connector.close()