[Bugfix][KV Connector] Propagate cache reset failure during sleep (#54581)

Signed-off-by: CrazyCoder <18235787078@163.com>
Signed-off-by: aoshen02 <aoshen@inferact.ai>
Co-authored-by: aoshen02 <aoshen@inferact.ai>
Co-authored-by: Codex <noreply@openai.com>

vllm/v1/engine/core.py

@@ -867,10 +867,11 @@ class EngineCore:
         # reset_connector=True so external connectors clear alongside
         # local caches, matching the pause_generation(clear_cache=True)
         # contract. No-op when no connector is configured.
-        self.reset_prefix_cache(
+        if not self.reset_prefix_cache(
             reset_running_requests=reset_running_requests,
             reset_connector=reset_connector,
-        )
+        ):
+            raise RuntimeError("Failed to reset the KV connector cache.")
         self.reset_mm_cache()
         self.reset_encoder_cache()
 
@@ -2001,8 +2002,12 @@ class EngineCoreProc(EngineCore):
             raise ValueError(f"Invalid pause mode: {mode}")
 
         def engine_idle_callback(engine: "EngineCoreProc", future: Future[Any]) -> None:
-            engine._finish_pause(clear_cache)
-            future.set_result(None)
+            try:
+                engine._finish_pause(clear_cache)
+            except Exception as e:
+                future.set_exception(e)
+            else:
+                future.set_result(None)
 
         if mode == "abort":
             aborted_reqs = self.scheduler.finish_requests(