api_server.py

import argparse
import asyncio
import json
from contextlib import asynccontextmanager
import os
import importlib
import inspect

from aioprometheus import MetricsMiddleware
from aioprometheus.asgi.starlette import metrics
import fastapi
import uvicorn
from http import HTTPStatus
from fastapi import Request
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse, StreamingResponse, Response

from vllm.engine.arg_utils import AsyncEngineArgs
from vllm.engine.async_llm_engine import AsyncLLMEngine
from vllm.engine.metrics import add_global_metrics_labels
from vllm.entrypoints.openai.protocol import CompletionRequest, ChatCompletionRequest, ErrorResponse
from vllm.logger import init_logger
from vllm.entrypoints.openai.serving_chat import OpenAIServingChat
from vllm.entrypoints.openai.serving_completion import OpenAIServingCompletion

TIMEOUT_KEEP_ALIVE = 5  # seconds

openai_serving_chat: OpenAIServingChat = None
openai_serving_completion: OpenAIServingCompletion = None
logger = init_logger(__name__)


@asynccontextmanager
async def lifespan(app: fastapi.FastAPI):

    async def _force_log():
        while True:
            await asyncio.sleep(10)
            await engine.do_log_stats()

    if not engine_args.disable_log_stats:
        asyncio.create_task(_force_log())

    yield


app = fastapi.FastAPI(lifespan=lifespan)


def parse_args():
    parser = argparse.ArgumentParser(
        description="vLLM OpenAI-Compatible RESTful API server.")
    parser.add_argument("--host", type=str, default=None, help="host name")
    parser.add_argument("--port", type=int, default=8000, help="port number")
    parser.add_argument("--allow-credentials",
                        action="store_true",
                        help="allow credentials")
    parser.add_argument("--allowed-origins",
                        type=json.loads,
                        default=["*"],
                        help="allowed origins")
    parser.add_argument("--allowed-methods",
                        type=json.loads,
                        default=["*"],
                        help="allowed methods")
    parser.add_argument("--allowed-headers",
                        type=json.loads,
                        default=["*"],
                        help="allowed headers")
    parser.add_argument(
        "--api-key",
        type=str,
        default=None,
        help=
        "If provided, the server will require this key to be presented in the header."
    )
    parser.add_argument("--served-model-name",
                        type=str,
                        default=None,
                        help="The model name used in the API. If not "
                        "specified, the model name will be the same as "
                        "the huggingface name.")
    parser.add_argument("--chat-template",
                        type=str,
                        default=None,
                        help="The file path to the chat template, "
                        "or the template in single-line form "
                        "for the specified model")
    parser.add_argument("--response-role",
                        type=str,
                        default="assistant",
                        help="The role name to return if "
                        "`request.add_generation_prompt=true`.")
    parser.add_argument("--ssl-keyfile",
                        type=str,
                        default=None,
                        help="The file path to the SSL key file")
    parser.add_argument("--ssl-certfile",
                        type=str,
                        default=None,
                        help="The file path to the SSL cert file")
    parser.add_argument(
        "--root-path",
        type=str,
        default=None,
        help="FastAPI root_path when app is behind a path based routing proxy")
    parser.add_argument(
        "--middleware",
        type=str,
        action="append",
        default=[],
        help="Additional ASGI middleware to apply to the app. "
        "We accept multiple --middleware arguments. "
        "The value should be an import path. "
        "If a function is provided, vLLM will add it to the server using @app.middleware('http'). "
        "If a class is provided, vLLM will add it to the server using app.add_middleware(). "
    )

    parser = AsyncEngineArgs.add_cli_args(parser)
    return parser.parse_args()


app.add_middleware(MetricsMiddleware)  # Trace HTTP server metrics
app.add_route("/metrics", metrics)  # Exposes HTTP metrics


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(_, exc):
    err = openai_serving_chat.create_error_response(message=str(exc))
    return JSONResponse(err.model_dump(), status_code=HTTPStatus.BAD_REQUEST)


@app.get("/health")
async def health() -> Response:
    """Health check."""
    return Response(status_code=200)


@app.get("/v1/models")
async def show_available_models():
    models = await openai_serving_chat.show_available_models()
    return JSONResponse(content=models.model_dump())


@app.post("/v1/chat/completions")
async def create_chat_completion(request: ChatCompletionRequest,
                                 raw_request: Request):
    generator = await openai_serving_chat.create_chat_completion(
        request, raw_request)
    if isinstance(generator, ErrorResponse):
        return JSONResponse(content=generator.model_dump(),
                            status_code=generator.code)
    if request.stream:
        return StreamingResponse(content=generator,
                                 media_type="text/event-stream")
    else:
        return JSONResponse(content=generator.model_dump())


@app.post("/v1/completions")
async def create_completion(request: CompletionRequest, raw_request: Request):
    generator = await openai_serving_completion.create_completion(
        request, raw_request)
    if isinstance(generator, ErrorResponse):
        return JSONResponse(content=generator.model_dump(),
                            status_code=generator.code)
    if request.stream:
        return StreamingResponse(content=generator,
                                 media_type="text/event-stream")
    else:
        return JSONResponse(content=generator.model_dump())


if __name__ == "__main__":
    args = parse_args()

    app.add_middleware(
        CORSMiddleware,
        allow_origins=args.allowed_origins,
        allow_credentials=args.allow_credentials,
        allow_methods=args.allowed_methods,
        allow_headers=args.allowed_headers,
    )

    if token := os.environ.get("VLLM_API_KEY") or args.api_key:

        @app.middleware("http")
        async def authentication(request: Request, call_next):
            if not request.url.path.startswith("/v1"):
                return await call_next(request)
            if request.headers.get("Authorization") != "Bearer " + token:
                return JSONResponse(content={"error": "Unauthorized"},
                                    status_code=401)
            return await call_next(request)

    for middleware in args.middleware:
        module_path, object_name = middleware.rsplit(".", 1)
        imported = getattr(importlib.import_module(module_path), object_name)
        if inspect.isclass(imported):
            app.add_middleware(imported)
        elif inspect.iscoroutinefunction(imported):
            app.middleware("http")(imported)
        else:
            raise ValueError(
                f"Invalid middleware {middleware}. Must be a function or a class."
            )

    logger.info(f"args: {args}")

    if args.served_model_name is not None:
        served_model = args.served_model_name
    else:
        served_model = args.model

    engine_args = AsyncEngineArgs.from_cli_args(args)
    engine = AsyncLLMEngine.from_engine_args(engine_args)
    openai_serving_chat = OpenAIServingChat(engine, served_model,
                                            args.response_role,
                                            args.chat_template)
    openai_serving_completion = OpenAIServingCompletion(engine, served_model)

    # Register labels for metrics
    add_global_metrics_labels(model_name=engine_args.model)

    app.root_path = args.root_path
    uvicorn.run(app,
                host=args.host,
                port=args.port,
                log_level="info",
                timeout_keep_alive=TIMEOUT_KEEP_ALIVE,
                ssl_keyfile=args.ssl_keyfile,
                ssl_certfile=args.ssl_certfile)