[HiCache] fix: graceful shutdown of pending async tasks in bench_mix.py (#20276)

benchmark/hicache/bench_mix.py

@@ -426,11 +426,13 @@ class WorkloadGenerator:
 
     def request_sender(self):
         async def request_loop():
+            tasks = []
             while True:
                 if self.sent_requests - self.completed_requests < self.max_parallel:
                     new_request = self.user_generator.pop()
                     if new_request:
-                        asyncio.create_task(self.handle_request(new_request))
+                        task = asyncio.create_task(self.handle_request(new_request))
+                        tasks.append(task)
                         self.sent_requests += 1
                 else:
                     await asyncio.sleep(0.05)
@@ -440,6 +442,11 @@ class WorkloadGenerator:
                     self.done = True
                     break
 
+            # Cancel all pending tasks and wait for them to finish
+            for task in tasks:
+                task.cancel()
+            await asyncio.gather(*tasks, return_exceptions=True)
+
         loop = asyncio.new_event_loop()
         asyncio.set_event_loop(loop)
         loop.run_until_complete(request_loop())