更新

backend/tests/test_traffic_control.py

@@ -458,6 +458,70 @@ class BackgroundTrafficLimitTests(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(len(tasks_seen), 3)
         self.assertTrue(all(task is tasks_seen[0] for task in tasks_seen))
 
+    async def test_startup_request_is_not_buried_behind_normal_backlog(self):
+        with patch.dict(
+            os.environ,
+            {"KEFU_BACKGROUND_NETWORK_CONCURRENCY": "1"},
+        ):
+            controller = TrafficController()
+        self.addAsyncCleanup(controller.stop)
+
+        entered: list[str] = []
+        releases = {
+            name: asyncio.Event()
+            for name in ("active", "normal-1", "normal-2", "startup")
+        }
+
+        async def request(name: str, *, startup: bool = False) -> None:
+            async with controller.background_slot(
+                1,
+                name,
+                startup=startup,
+            ):
+                entered.append(name)
+                await releases[name].wait()
+
+        active = asyncio.create_task(request("active"))
+        while entered != ["active"]:
+            await asyncio.sleep(0)
+
+        normal_one = asyncio.create_task(request("normal-1"))
+        normal_two = asyncio.create_task(request("normal-2"))
+        # Let one normal request reach the shared semaphore while the other is
+        # held at normal admission, then add the priority startup request.
+        await asyncio.sleep(0)
+        await asyncio.sleep(0)
+        startup = asyncio.create_task(request("startup", startup=True))
+        await asyncio.sleep(0)
+
+        releases["active"].set()
+        while len(entered) < 2:
+            await asyncio.sleep(0)
+        self.assertEqual(entered[:2], ["active", "normal-1"])
+
+        releases["normal-1"].set()
+        while len(entered) < 3:
+            await asyncio.sleep(0)
+        self.assertEqual(entered[:3], ["active", "normal-1", "startup"])
+
+        releases["startup"].set()
+        while len(entered) < 4:
+            await asyncio.sleep(0)
+        releases["normal-2"].set()
+        await asyncio.wait_for(
+            asyncio.gather(active, normal_one, normal_two, startup),
+            timeout=0.2,
+        )
+
+        self.assertEqual(
+            entered,
+            ["active", "normal-1", "startup", "normal-2"],
+        )
+        self.assertEqual(controller.background_active, 0)
+        self.assertEqual(controller.background_waiting, 0)
+        self.assertEqual(controller.background_startup_active, 0)
+        self.assertEqual(controller.background_startup_waiting, 0)
+
 
 class TrafficControllerLoopIsolationTests(unittest.TestCase):
     def test_get_traffic_controller_does_not_reuse_asyncio_primitives(self):