Tiny simplify draft worker init. (#16446)

python/sglang/srt/managers/scheduler.py

@@ -481,7 +481,11 @@ class Scheduler(
             nccl_port=self.nccl_port,
         )
 
-    def init_draft_worker(self):
+    def maybe_init_draft_worker(self):
+        if self.spec_algorithm.is_none():
+            self.draft_worker = None
+            return
+
         # Launch a draft worker for speculative decoding
         draft_worker_kwargs = dict(
             server_args=self.server_args,
@@ -501,50 +505,12 @@ class Scheduler(
                 f"Using draft model load_format: '{self.server_args.speculative_draft_load_format}'"
             )
 
-        # FIXME: refactor the draft worker registration logic
-        if self.server_args.enable_multi_layer_eagle:
-            if self.enable_overlap:
-                from sglang.srt.speculative.multi_layer_eagle_worker_v2 import (
-                    MultiLayerEagleWorkerV2,
-                )
-
-                self.draft_worker = MultiLayerEagleWorkerV2(
-                    gpu_id=self.gpu_id,
-                    tp_rank=self.tp_rank,
-                    moe_ep_rank=self.moe_ep_rank,
-                    server_args=self.server_args,
-                    nccl_port=self.nccl_port,
-                    target_worker=self.tp_worker,
-                    dp_rank=self.dp_rank,
-                )
-            else:
-                from sglang.srt.speculative.multi_layer_eagle_worker import (
-                    MultiLayerEagleWorker,
-                )
-
-                self.draft_worker = MultiLayerEagleWorker(
-                    gpu_id=self.gpu_id,
-                    tp_rank=self.tp_rank,
-                    moe_ep_rank=self.moe_ep_rank,
-                    server_args=self.server_args,
-                    nccl_port=self.nccl_port,
-                    target_worker=self.tp_worker,
-                    dp_rank=self.dp_rank,
-                )
-        else:
-            WorkerClass = self.spec_algorithm.create_worker(
-                enable_overlap=self.enable_overlap
-            )
-
-            # FIXME: optimize the init draft worker code path
-            if WorkerClass is not None:
-                self.draft_worker = WorkerClass(**draft_worker_kwargs)
-            else:
-                self.draft_worker = None
+        DraftWorkerClass = self.spec_algorithm.create_worker(self.server_args)
+        self.draft_worker = DraftWorkerClass(**draft_worker_kwargs)
 
     def init_model_worker(self):
         self.init_tp_model_worker()
-        self.init_draft_worker()
+        self.maybe_init_draft_worker()
 
         # Dispatch the model worker
         if self.spec_algorithm.is_none():

python/sglang/srt/speculative/spec_info.py

@@ -7,6 +7,7 @@ from typing import TYPE_CHECKING, List, Optional, Tuple, Type, Union
 if TYPE_CHECKING:
     from sglang.srt.managers.schedule_batch import ModelWorkerBatch
     from sglang.srt.managers.tp_worker import TpModelWorker
+    from sglang.srt.server_args import ServerArgs
     from sglang.srt.speculative.base_spec_worker import BaseSpecWorker
     from sglang.srt.speculative.ngram_worker import NGRAMWorker
 
@@ -49,12 +50,29 @@ class SpeculativeAlgorithm(Enum):
         return self.is_eagle() or self.is_standalone()
 
     def create_worker(
-        self, enable_overlap: bool = False
+        self, server_args: ServerArgs
     ) -> Optional[Union[Type[BaseSpecWorker], Type[TpModelWorker], Type[NGRAMWorker]]]:
-        if self.is_none():
-            return None
+        assert (
+            not self.is_none()
+        ), "Cannot create worker for NONE speculative algorithm."
 
-        if self.is_eagle():
+        enable_overlap = not server_args.disable_overlap_schedule
+        if self.is_eagle() and server_args.enable_multi_layer_eagle:
+            # FIXME: migrate to EagleWorker
+            if enable_overlap:
+                from sglang.srt.speculative.multi_layer_eagle_worker_v2 import (
+                    MultiLayerEagleWorkerV2,
+                )
+
+                return MultiLayerEagleWorkerV2
+
+            from sglang.srt.speculative.multi_layer_eagle_worker import (
+                MultiLayerEagleWorker,
+            )
+
+            return MultiLayerEagleWorker
+
+        elif self.is_eagle():
             if enable_overlap:
                 from sglang.srt.speculative.eagle_worker_v2 import EAGLEWorkerV2