[core][V1] pluggable scheduler (#14466)

Signed-off-by: Joe Runde <Joseph.Runde@ibm.com>

vllm/v1/engine/core.py

@@ -19,9 +19,10 @@ from vllm.logger import init_logger
 from vllm.lora.request import LoRARequest
 from vllm.transformers_utils.config import (
     maybe_register_config_serialize_by_value)
-from vllm.utils import get_exception_traceback, zmq_socket_ctx
+from vllm.utils import (get_exception_traceback, resolve_obj_by_qualname,
+                        zmq_socket_ctx)
 from vllm.v1.core.kv_cache_utils import get_kv_cache_configs
-from vllm.v1.core.scheduler import Scheduler, SchedulerOutput
+from vllm.v1.core.scheduler import SchedulerOutput
 from vllm.v1.engine import (EngineCoreOutputs, EngineCoreRequest,
                             EngineCoreRequestType, UtilityOutput)
 from vllm.v1.engine.mm_input_cache import MMInputCacheServer
@@ -65,6 +66,16 @@ class EngineCore:
         self.structured_output_manager = StructuredOutputManager(vllm_config)
 
         # Setup scheduler.
+        if isinstance(vllm_config.scheduler_config.scheduler_cls, str):
+            logger.warning(
+                "Using configured V1 scheduler class %s. "
+                "This scheduler interface is not public and "
+                "compatibility may not be maintained.",
+                vllm_config.scheduler_config.scheduler_cls)
+            Scheduler = resolve_obj_by_qualname(
+                vllm_config.scheduler_config.scheduler_cls)
+        else:
+            Scheduler = vllm_config.scheduler_config.scheduler_cls
         self.scheduler = Scheduler(
             scheduler_config=vllm_config.scheduler_config,
             model_config=vllm_config.model_config,