[Frontend] Split `OpenAIServingModels` into `OpenAIModelRegistry` + `OpenAIServingModels` (#36536)

Signed-off-by: Sage Ahrac <sagiahrak@gmail.com>

vllm/entrypoints/openai/api_server.py

@@ -414,11 +414,19 @@ async def init_render_app_state(
     directly from the :class:`~vllm.config.VllmConfig`.
     """
     from vllm.entrypoints.chat_utils import load_chat_template
+    from vllm.entrypoints.openai.models.serving import OpenAIModelRegistry
     from vllm.entrypoints.serve.render.serving import OpenAIServingRender
     from vllm.plugins.io_processors import get_io_processor
     from vllm.renderers import renderer_from_config
 
     served_model_names = args.served_model_name or [args.model]
+    model_registry = OpenAIModelRegistry(
+        model_config=vllm_config.model_config,
+        base_model_paths=[
+            BaseModelPath(name=name, model_path=args.model)
+            for name in served_model_names
+        ],
+    )
 
     if args.enable_log_requests:
         request_logger = RequestLogger(max_log_len=args.max_log_len)
@@ -435,7 +443,7 @@ async def init_render_app_state(
         model_config=vllm_config.model_config,
         renderer=renderer,
         io_processor=io_processor,
-        served_model_names=served_model_names,
+        model_registry=model_registry,
         request_logger=request_logger,
         chat_template=resolved_chat_template,
         chat_template_content_format=args.chat_template_content_format,
@@ -447,8 +455,7 @@ async def init_render_app_state(
         log_error_stack=args.log_error_stack,
     )
 
-    # Expose models endpoint via the render handler.
-    state.openai_serving_models = state.openai_serving_render
+    state.openai_serving_models = model_registry
 
     state.vllm_config = vllm_config
     # Disable stats logging — there is no engine to poll.

vllm/entrypoints/openai/generate/api_router.py

@@ -169,9 +169,7 @@ async def init_generate_state(
         model_config=engine_client.model_config,
         renderer=engine_client.renderer,
         io_processor=engine_client.io_processor,
-        served_model_names=[
-            mp.name for mp in state.openai_serving_models.base_model_paths
-        ],
+        model_registry=state.openai_serving_models.registry,
         request_logger=request_logger,
         chat_template=resolved_chat_template,
         chat_template_content_format=args.chat_template_content_format,

vllm/entrypoints/openai/models/serving.py

@@ -5,6 +5,7 @@ from asyncio import Lock
 from collections import defaultdict
 from http import HTTPStatus
 
+from vllm.config import ModelConfig
 from vllm.engine.protocol import EngineClient
 from vllm.entrypoints.openai.engine.protocol import (
     ErrorResponse,
@@ -27,6 +28,51 @@ from vllm.utils.counter import AtomicCounter
 logger = init_logger(__name__)
 
 
+class OpenAIModelRegistry:
+    """Read-only view of the loaded base models with no engine dependency.
+
+    Suitable for CPU-only / render-only contexts that have no engine client
+    and no LoRA support.
+    """
+
+    def __init__(
+        self,
+        model_config: ModelConfig,
+        base_model_paths: list[BaseModelPath],
+    ) -> None:
+        self.model_config = model_config
+        self.base_model_paths = base_model_paths
+
+    def is_base_model(self, model_name: str) -> bool:
+        return any(model.name == model_name for model in self.base_model_paths)
+
+    async def check_model(self, model_name: str | None) -> ErrorResponse | None:
+        """Return an ErrorResponse if model_name is not served, else None."""
+        if not model_name or self.is_base_model(model_name):
+            return None
+        return create_error_response(
+            message=f"The model `{model_name}` does not exist.",
+            err_type="NotFoundError",
+            status_code=HTTPStatus.NOT_FOUND,
+            param="model",
+        )
+
+    async def show_available_models(self) -> ModelList:
+        """Show available models (base models only)."""
+        max_model_len = self.model_config.max_model_len
+        return ModelList(
+            data=[
+                ModelCard(
+                    id=base_model.name,
+                    max_model_len=max_model_len,
+                    root=base_model.model_path,
+                    permission=[ModelPermission()],
+                )
+                for base_model in self.base_model_paths
+            ]
+        )
+
+
 class OpenAIServingModels:
     """Shared instance to hold data about the loaded base model(s) and adapters.
 
@@ -45,6 +91,11 @@ class OpenAIServingModels:
     ):
         super().__init__()
 
+        self.registry = OpenAIModelRegistry(
+            model_config=engine_client.model_config,
+            base_model_paths=base_model_paths,
+        )
+
         self.engine_client = engine_client
         self.base_model_paths = base_model_paths
 
@@ -79,34 +130,18 @@ class OpenAIServingModels:
             if isinstance(load_result, ErrorResponse):
                 raise ValueError(load_result.error.message)
 
-    def is_base_model(self, model_name) -> bool:
-        return any(model.name == model_name for model in self.base_model_paths)
+    def is_base_model(self, model_name: str) -> bool:
+        return self.registry.is_base_model(model_name)
 
     def model_name(self, lora_request: LoRARequest | None = None) -> str:
-        """Returns the appropriate model name depending on the availability
-        and support of the LoRA or base model.
-        Parameters:
-        - lora: LoRARequest that contain a base_model_name.
-        Returns:
-        - str: The name of the base model or the first available model path.
-        """
         if lora_request is not None:
             return lora_request.lora_name
         return self.base_model_paths[0].name
 
     async def show_available_models(self) -> ModelList:
-        """Show available models. This includes the base model and all adapters."""
-        max_model_len = self.model_config.max_model_len
-
-        model_cards = [
-            ModelCard(
-                id=base_model.name,
-                max_model_len=max_model_len,
-                root=base_model.model_path,
-                permission=[ModelPermission()],
-            )
-            for base_model in self.base_model_paths
-        ]
+        """Show available models. This includes the base model and all
+        adapters."""
+        model_list = await self.registry.show_available_models()
         lora_cards = [
             ModelCard(
                 id=lora.lora_name,
@@ -118,8 +153,8 @@ class OpenAIServingModels:
             )
             for lora in self.lora_requests.values()
         ]
-        model_cards.extend(lora_cards)
-        return ModelList(data=model_cards)
+        model_list.data.extend(lora_cards)
+        return model_list
 
     async def load_lora_adapter(
         self, request: LoadLoRAAdapterRequest, base_model_name: str | None = None

vllm/entrypoints/serve/render/serving.py

@@ -16,10 +16,8 @@ from vllm.entrypoints.openai.chat_completion.protocol import ChatCompletionReque
 from vllm.entrypoints.openai.completion.protocol import CompletionRequest
 from vllm.entrypoints.openai.engine.protocol import (
     ErrorResponse,
-    ModelCard,
-    ModelList,
-    ModelPermission,
 )
+from vllm.entrypoints.openai.models.serving import OpenAIModelRegistry
 from vllm.entrypoints.openai.parser.harmony_utils import (
     get_developer_message,
     get_system_message,
@@ -46,7 +44,7 @@ class OpenAIServingRender:
         model_config: ModelConfig,
         renderer: BaseRenderer,
         io_processor: Any,
-        served_model_names: list[str],
+        model_registry: OpenAIModelRegistry,
         *,
         request_logger: RequestLogger | None,
         chat_template: str | None,
@@ -61,7 +59,7 @@ class OpenAIServingRender:
         self.model_config = model_config
         self.renderer = renderer
         self.io_processor = io_processor
-        self.served_model_names = served_model_names
+        self.model_registry = model_registry
         self.request_logger = request_logger
         self.chat_template = chat_template
         self.chat_template_content_format: ChatTemplateContentFormatOption = (
@@ -252,21 +250,6 @@ class OpenAIServingRender:
 
         return messages, [engine_prompt]
 
-    async def show_available_models(self) -> ModelList:
-        """Returns the models served by this render server."""
-        max_model_len = self.model_config.max_model_len
-        return ModelList(
-            data=[
-                ModelCard(
-                    id=name,
-                    max_model_len=max_model_len,
-                    root=self.model_config.model,
-                    permission=[ModelPermission()],
-                )
-                for name in self.served_model_names
-            ]
-        )
-
     def create_error_response(
         self,
         message: str | Exception,
@@ -276,23 +259,11 @@ class OpenAIServingRender:
     ) -> ErrorResponse:
         return create_error_response(message, err_type, status_code, param)
 
-    def _is_model_supported(self, model_name: str) -> bool:
-        """Simplified from OpenAIServing._is_model_supported (no LoRA support)."""
-        return model_name in self.served_model_names
-
     async def _check_model(
         self,
         request: Any,
     ) -> ErrorResponse | None:
-        """Simplified from OpenAIServing._check_model (no LoRA support)."""
-        if self._is_model_supported(request.model):
-            return None
-        return self.create_error_response(
-            message=f"The model `{request.model}` does not exist.",
-            err_type="NotFoundError",
-            status_code=HTTPStatus.NOT_FOUND,
-            param="model",
-        )
+        return await self.model_registry.check_model(request.model)
 
     def _validate_chat_template(
         self,