chore: add check for closed connector

Author: kgala2

google/cloud/sql/connector/connector.py

@@ -153,6 +153,7 @@ def __init__(
         # connection name string and enable_iam_auth boolean flag
         self._cache: dict[tuple[str, bool], MonitoredCache] = {}
         self._client: Optional[CloudSQLClient] = None
+        self._closed: bool = False
 
         # initialize credentials
         scopes = ["https://www.googleapis.com/auth/sqlservice.admin"]
@@ -279,7 +280,11 @@ async def connect_async(
                 and then subsequent attempt with IAM database authentication.
             KeyError: Unsupported database driver Must be one of pymysql, asyncpg,
                 pg8000, and pytds.
+            RuntimeError: Connector has been closed. Cannot connect using a closed
+                Connector.
         """
+        if self._closed:
+            raise RuntimeError("Cannot connect using a closed Connector.")
         if self._keys is None:
             self._keys = asyncio.create_task(generate_keys())
         if self._client is None:
@@ -462,13 +467,15 @@ def close(self) -> None:
                 self._loop.call_soon_threadsafe(self._loop.stop)
             # wait for thread to finish closing (i.e. loop to stop)
             self._thread.join()
+        self._closed = True
 
     async def close_async(self) -> None:
         """Helper function to cancel the cache's tasks
         and close aiohttp.ClientSession."""
         await asyncio.gather(*[cache.close() for cache in self._cache.values()])
         if self._client:
             await self._client.close()
+        self._closed = True
 
 
 async def create_async_connector(

tests/unit/test_connector.py

@@ -1,19 +1,3 @@
-"""
-Copyright 2021 Google LLC
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-  https://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-"""
-
 import asyncio
 import os
 from typing import Union
@@ -468,3 +452,42 @@ def test_configured_quota_project_env_var(
         assert connector._quota_project == quota_project
     # unset env var
     del os.environ["GOOGLE_CLOUD_QUOTA_PROJECT"]
+
+
+@pytest.mark.asyncio
+async def test_connect_async_closed_connector(
+    fake_credentials: Credentials, fake_client: CloudSQLClient
+) -> None:
+    """Test that calling connect_async() on a closed connector raises an error."""
+    async with Connector(
+        credentials=fake_credentials, loop=asyncio.get_running_loop()
+    ) as connector:
+        connector._client = fake_client
+        await connector.close_async()
+        with pytest.raises(RuntimeError) as exc_info:
+            await connector.connect_async(
+                "test-project:test-region:test-instance",
+                "asyncpg",
+                user="my-user",
+                password="my-pass",
+                db="my-db",
+            )
+        assert exc_info.value.args[0] == "Cannot connect using a closed Connector."
+
+
+def test_connect_closed_connector(
+    fake_credentials: Credentials, fake_client: CloudSQLClient
+) -> None:
+    """Test that calling connect() on a closed connector raises an error."""
+    with Connector(credentials=fake_credentials) as connector:
+        connector._client = fake_client
+        connector.close()
+        with pytest.raises(RuntimeError) as exc_info:
+            connector.connect(
+                "test-project:test-region:test-instance",
+                "pg8000",
+                user="my-user",
+                password="my-pass",
+                db="my-db",
+            )
+        assert exc_info.value.args[0] == "Cannot connect using a closed Connector."