[Bugfix] Fix TypeError in scheduler when comparing mixed request_id types (#21816)

Signed-off-by: chiliu <chiliu@paypal.com>
Co-authored-by: chiliu <chiliu@paypal.com>

tests/v1/engine/test_engine_core.py

@@ -236,7 +236,7 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
     Test that the engine can handle multiple concurrent batches.
     """
 
-    def make_request_with_max_tokens(req_id: int,
+    def make_request_with_max_tokens(req_id: str,
                                      max_tokens: int) -> EngineCoreRequest:
         request = make_request()
         request.request_id = req_id
@@ -297,16 +297,16 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
         assert engine_core.batch_queue is not None
 
         # Add two requests in a row. Each request have 12 prompt tokens.
-        req0 = make_request_with_max_tokens(0, 5)
+        req0 = make_request_with_max_tokens("0", 5)
         engine_core.add_request(req0)
-        req1 = make_request_with_max_tokens(1, 5)
+        req1 = make_request_with_max_tokens("1", 5)
         engine_core.add_request(req1)
 
         # Schedule Batch 1: (10, req0)
         assert engine_core.step_with_batch_queue()[0] is None
         assert engine_core.batch_queue.qsize() == 1
         scheduler_output = engine_core.batch_queue.queue[-1][1]
-        assert scheduler_output.num_scheduled_tokens[0] == 10
+        assert scheduler_output.num_scheduled_tokens["0"] == 10
         # num_computed_tokens should have been updated immediately.
         assert engine_core.scheduler.requests[
             req0.request_id].num_computed_tokens == 10
@@ -315,11 +315,11 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
         assert engine_core.step_with_batch_queue()[0] is None
         assert engine_core.batch_queue.qsize() == 2
         scheduler_output = engine_core.batch_queue.queue[-1][1]
-        assert scheduler_output.num_scheduled_tokens[0] == 2
-        assert scheduler_output.num_scheduled_tokens[1] == 8
+        assert scheduler_output.num_scheduled_tokens["0"] == 2
+        assert scheduler_output.num_scheduled_tokens["1"] == 8
         # num_computed_tokens should have been updated immediately.
-        assert engine_core.scheduler.requests[0].num_computed_tokens == 12
-        assert engine_core.scheduler.requests[1].num_computed_tokens == 8
+        assert engine_core.scheduler.requests["0"].num_computed_tokens == 12
+        assert engine_core.scheduler.requests["1"].num_computed_tokens == 8
 
         assert engine_core.scheduler.get_num_unfinished_requests() == 2
 
@@ -331,7 +331,7 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
         engine_core.step_with_batch_queue()
         assert engine_core.batch_queue.qsize() == 2
         scheduler_output = engine_core.batch_queue.queue[-1][1]
-        assert scheduler_output.num_scheduled_tokens[1] == 4
+        assert scheduler_output.num_scheduled_tokens["1"] == 4
 
         # Batch queue is full. Finish Batch 2. Get first token of req0.
         output = engine_core.step_with_batch_queue()[0].get(0)
@@ -343,7 +343,7 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
         engine_core.step_with_batch_queue()
         assert engine_core.batch_queue.qsize() == 2
         scheduler_output = engine_core.batch_queue.queue[-1][1]
-        assert scheduler_output.num_scheduled_tokens[0] == 1
+        assert scheduler_output.num_scheduled_tokens["0"] == 1
 
         # Batch queue is full. Finish Batch 3. Get first token of req1.
         output = engine_core.step_with_batch_queue()[0].get(0)
@@ -355,14 +355,14 @@ def test_engine_core_concurrent_batches(monkeypatch: pytest.MonkeyPatch):
         engine_core.step_with_batch_queue()
         assert engine_core.batch_queue.qsize() == 2
         scheduler_output = engine_core.batch_queue.queue[-1][1]
-        assert scheduler_output.num_scheduled_tokens[1] == 1
+        assert scheduler_output.num_scheduled_tokens["1"] == 1
 
         # Loop until req0 is finished.
         step = 0
         req_id = 0
         expected_num_tokens = [
-            engine_core.scheduler.requests[0].num_tokens + 1,
-            engine_core.scheduler.requests[1].num_tokens + 1,
+            engine_core.scheduler.requests["0"].num_tokens + 1,
+            engine_core.scheduler.requests["1"].num_tokens + 1,
         ]
         while engine_core.scheduler.get_num_unfinished_requests() == 2:
             output = engine_core.step_with_batch_queue()[0]
@@ -413,3 +413,49 @@ def test_engine_core_tp(monkeypatch: pytest.MonkeyPatch):
             get_worker_cache_config_field, args=("num_cpu_blocks", ))
         assert all(x is not None for x in num_gpu_blocks)
         assert all(x is not None for x in num_cpu_blocks)
+
+
+@create_new_process_for_each_test()
+def test_engine_core_invalid_request_id_type(monkeypatch: pytest.MonkeyPatch):
+    """Test that engine raises TypeError for non-string request_id."""
+    with monkeypatch.context() as m:
+        m.setenv("VLLM_USE_V1", "1")
+
+        engine_args = EngineArgs(model=MODEL_NAME)
+        vllm_config = engine_args.create_engine_config()
+        executor_class = Executor.get_class(vllm_config)
+
+        with set_default_torch_num_threads(1):
+            engine_core = EngineCore(vllm_config=vllm_config,
+                                     executor_class=executor_class,
+                                     log_stats=True)
+
+        # Test with UUID object (common mistake)
+        uuid_request = make_request()
+        uuid_request.request_id = uuid.uuid4()  # UUID object instead of string
+
+        with pytest.raises(TypeError,
+                           match="request_id must be a string, got.*UUID"):
+            engine_core.add_request(uuid_request)
+
+        # Test with integer
+        int_request = make_request()
+        int_request.request_id = 12345
+
+        with pytest.raises(TypeError,
+                           match="request_id must be a string, got.*int"):
+            engine_core.add_request(int_request)
+
+        # Test with None
+        none_request = make_request()
+        none_request.request_id = None
+
+        with pytest.raises(TypeError,
+                           match="request_id must be a string, got.*NoneType"):
+            engine_core.add_request(none_request)
+
+        # Verify engine is still functional after errors
+        valid_request = make_request()
+        engine_core.add_request(valid_request)
+        assert len(engine_core.scheduler.waiting) == 1
+        assert len(engine_core.scheduler.running) == 0

vllm/v1/engine/core.py

@@ -207,6 +207,11 @@ class EngineCore:
 
     def add_request(self, request: EngineCoreRequest):
         """Add request to the scheduler."""
+        # Validate the request_id type.
+        if not isinstance(request.request_id, str):
+            raise TypeError(
+                f"request_id must be a string, got {type(request.request_id)}")
+
         if pooling_params := request.pooling_params:
             supported_pooling_tasks = [
                 task for task in self.get_supported_tasks()