[Frontend] Add GPU-less render serving path (vllm launch render) (#36166)

vllm/entrypoints/openai/api_server.py

@@ -22,6 +22,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from starlette.datastructures import State
 
 import vllm.envs as envs
+from vllm.config import VllmConfig
 from vllm.engine.arg_utils import AsyncEngineArgs
 from vllm.engine.protocol import EngineClient
 from vllm.entrypoints.chat_utils import load_chat_template
@@ -198,7 +199,7 @@ def build_app(
 
     register_sagemaker_api_router(app, supported_tasks)
 
-    if any(task in supported_tasks for task in ("generate", "render")):
+    if "generate" in supported_tasks:
         from vllm.entrypoints.openai.generate.api_router import (
             register_generate_api_routers,
         )
@@ -223,6 +224,13 @@ def build_app(
 
         elastic_ep_attach_router(app)
 
+    if "generate" in supported_tasks or "render" in supported_tasks:
+        from vllm.entrypoints.serve.render.api_router import (
+            attach_router as attach_render_router,
+        )
+
+        attach_render_router(app)
+
     if "transcription" in supported_tasks:
         from vllm.entrypoints.openai.speech_to_text.api_router import (
             attach_router as register_speech_to_text_api_router,
@@ -363,7 +371,7 @@ async def init_app_state(
         trust_request_chat_template=args.trust_request_chat_template,
     )
 
-    if any(task in supported_tasks for task in ("generate", "render")):
+    if "generate" in supported_tasks:
         from vllm.entrypoints.openai.generate.api_router import init_generate_state
 
         await init_generate_state(
@@ -393,6 +401,64 @@ async def init_app_state(
     state.server_load_metrics = 0
 
 
+async def init_render_app_state(
+    vllm_config: VllmConfig,
+    state: State,
+    args: Namespace,
+) -> None:
+    """Initialise FastAPI app state for a CPU-only render server.
+
+    Unlike :func:`init_app_state` this function does not require an
+    :class:`~vllm.engine.protocol.EngineClient`; it bootstraps the
+    preprocessing pipeline (renderer, io_processor, input_processor)
+    directly from the :class:`~vllm.config.VllmConfig`.
+    """
+    from vllm.entrypoints.chat_utils import load_chat_template
+    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]
+
+    if args.enable_log_requests:
+        request_logger = RequestLogger(max_log_len=args.max_log_len)
+    else:
+        request_logger = None
+
+    renderer = renderer_from_config(vllm_config)
+    io_processor = get_io_processor(
+        vllm_config, renderer, vllm_config.model_config.io_processor_plugin
+    )
+    resolved_chat_template = load_chat_template(args.chat_template)
+
+    state.openai_serving_render = OpenAIServingRender(
+        model_config=vllm_config.model_config,
+        renderer=renderer,
+        io_processor=io_processor,
+        served_model_names=served_model_names,
+        request_logger=request_logger,
+        chat_template=resolved_chat_template,
+        chat_template_content_format=args.chat_template_content_format,
+        trust_request_chat_template=args.trust_request_chat_template,
+        enable_auto_tools=args.enable_auto_tool_choice,
+        exclude_tools_when_tool_choice_none=args.exclude_tools_when_tool_choice_none,
+        tool_parser=args.tool_call_parser,
+        default_chat_template_kwargs=args.default_chat_template_kwargs,
+        log_error_stack=args.log_error_stack,
+    )
+
+    # Expose models endpoint via the render handler.
+    state.openai_serving_models = state.openai_serving_render
+
+    state.vllm_config = vllm_config
+    # Disable stats logging — there is no engine to poll.
+    state.log_stats = False
+    state.engine_client = None
+    state.args = args
+    state.enable_server_load_tracking = False
+    state.server_load_metrics = 0
+
+
 def create_server_socket(addr: tuple[str, int]) -> socket.socket:
     family = socket.AF_INET
     if is_valid_ipv6_address(addr[0]):
@@ -494,7 +560,6 @@ async def build_and_serve(
 
     supported_tasks = await engine_client.get_supported_tasks()
     logger.info("Supported tasks: %s", supported_tasks)
-
     app = build_app(args, supported_tasks)
     await init_app_state(engine_client, app.state, args, supported_tasks)
 
@@ -522,6 +587,51 @@ async def build_and_serve(
     )
 
 
+async def build_and_serve_renderer(
+    vllm_config: VllmConfig,
+    listen_address: str,
+    sock: socket.socket,
+    args: Namespace,
+    **uvicorn_kwargs,
+) -> asyncio.Task:
+    """Build FastAPI app for a CPU-only render server, initialize state, and
+    start serving.
+
+    Returns the shutdown task for the caller to await.
+    """
+
+    # Get uvicorn log config (from file or with endpoint filter)
+    log_config = get_uvicorn_log_config(args)
+    if log_config is not None:
+        uvicorn_kwargs["log_config"] = log_config
+
+    app = build_app(args, ("render",))
+    await init_render_app_state(vllm_config, app.state, args)
+
+    logger.info("Starting vLLM server on %s", listen_address)
+
+    return await serve_http(
+        app,
+        sock=sock,
+        enable_ssl_refresh=args.enable_ssl_refresh,
+        host=args.host,
+        port=args.port,
+        log_level=args.uvicorn_log_level,
+        # NOTE: When the 'disable_uvicorn_access_log' value is True,
+        # no access log will be output.
+        access_log=not args.disable_uvicorn_access_log,
+        timeout_keep_alive=envs.VLLM_HTTP_TIMEOUT_KEEP_ALIVE,
+        ssl_keyfile=args.ssl_keyfile,
+        ssl_certfile=args.ssl_certfile,
+        ssl_ca_certs=args.ssl_ca_certs,
+        ssl_cert_reqs=args.ssl_cert_reqs,
+        ssl_ciphers=args.ssl_ciphers,
+        h11_max_incomplete_event_size=args.h11_max_incomplete_event_size,
+        h11_max_header_count=args.h11_max_header_count,
+        **uvicorn_kwargs,
+    )
+
+
 async def run_server(args, **uvicorn_kwargs) -> None:
     """Run a single-worker API server."""