[Feature] Pluggable platform-specific scheduler (#13161)

Signed-off-by: Yannick Schnider <yannick.schnider1@ibm.com>
Signed-off-by: Yannick Schnider <Yannick.Schnider1@ibm.com>

tests/plugins_tests/test_scheduler_plugins.py

@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: Apache-2.0
+
+from vllm.core.scheduler import Scheduler
+
+
+class DummyScheduler(Scheduler):
+
+    def schedule(self):
+        raise Exception("Exception raised by DummyScheduler")
+
+
+def test_scheduler_plugins():
+    import pytest
+
+    from vllm.engine.arg_utils import EngineArgs
+    from vllm.engine.llm_engine import LLMEngine
+    from vllm.sampling_params import SamplingParams
+
+    with pytest.raises(Exception) as exception_info:
+
+        engine_args = EngineArgs(
+            model="facebook/opt-125m",
+            enforce_eager=True,  # reduce test time
+            scheduler_cls=DummyScheduler,
+        )
+
+        engine = LLMEngine.from_engine_args(engine_args=engine_args)
+
+        sampling_params = SamplingParams(max_tokens=1)
+        engine.add_request("0", "foo", sampling_params)
+        engine.step()
+
+    assert str(exception_info.value) == "Exception raised by DummyScheduler"