FastAPI性能优化指南：参数解析与惰性加载

async def app(scope, receive, send):
    # 1. 请求解析阶段
    body = await receive()

    # 2. 参数验证阶段
    validated_data = await validate_request(body)

    # 3. 路由处理阶段
    response = await handle_request(validated_data)

    # 4. 响应序列化阶段
    await send(response)

from pydantic import BaseModel, validator


class OptimizedModel(BaseModel):
    id: int
    tags: list[str]

    class Config:
        # 启用ORM模式避免二次解析
        orm_mode = True
        # 禁止额外字段验证
        extra = 'forbid'
        # 验证器复用配置
        validate_assignment = True

    @validator('tags', pre=True)
    def split_tags(cls, v):
        return v.split(',') if isinstance(v, str) else v

from fastapi import Depends
from functools import lru_cache


class HeavyService:
    def __init__(self):
        self._conn = None  # 延迟初始化连接

    @property
    def conn(self):
        if not self._conn:
            self._conn = create_expensive_connection()
        return self._conn


@lru_cache(maxsize=32)
def get_service():
    return HeavyService()  # 应用级缓存


@app.get("/data")
async def get_data(svc: HeavyService = Depends(get_service)):
    return svc.conn.query()

async def async_db_conn():
    pool = await create_async_pool()
    try:
        yield pool
    finally:
        await pool.close()


@app.get("/async-data")
async def get_async_data(
        conn=Depends(async_db_conn)  # 按需初始化连接池
):
    async with conn.acquire() as session:
        return await session.execute(query)

from fastapi.encoders import jsonable_encoder
from orjson import orjson


def custom_json_parser(data: bytes):
    try:
        return orjson.loads(data)
    except orjson.JSONDecodeError as e:
        raise RequestValidationError(
            errors=[{'loc': ('body',), 'msg': 'Invalid JSON'}]
        )


app = FastAPI()
app.router.default_parser = custom_json_parser  # 替换默认解析器

from pydantic import BaseModel, Field


class TieredValidationModel(BaseModel):
    basic_info: dict = Field(..., alias='_basic')
    extended_info: dict = Field(None, validate_default=False)  # 延迟验证

    @validator('extended_info', always=True)
    def validate_extended(cls, v):
        # 仅在需要时验证
        return ExtendedValidator.parse(v)


@app.post("/tiered")
async def process_tiered(
        data: TieredValidationModel,
        need_extended: bool = False
):
    if need_extended:
        data.extended_info = data.validate_extended()
    return data

from fastapi import Request
from time import perf_counter_ns


@app.middleware("http")
async def metrics_middleware(request: Request, call_next):
    start = perf_counter_ns()
    response = await call_next(request)
    duration = (perf_counter_ns() - start) // 1_000_000

    request.state.metrics = {
        'path': request.url.path,
        'duration_ms': duration
    }
    return response

from fastapi.dependencies.utils import solve_dependencies


def profile_dependencies():
    for route in app.routes:
        dependant = route.dependant
        solved = solve_dependencies(dependant)
        for dep in solved.flat_graph():
            print(f"{dep.call.__name__}: {dep.cache_time}ms")

from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
    return JSONResponse(
        status_code=400,
        content={
            'code': 'INVALID_INPUT',
            'detail': exc.errors()
        }
    )