基于 FastAPI 和 OpenFeature 使用 Feature Flag 控制业务功能
模拟业务场景：多租户系统跨域转账，需要控制某租户下某用户是否可以在某域转账
open_feature_util.py
import typing
from abc import abstractmethod, ABCMeta
from typing import Sequencefrom openfeature.evaluation_context import EvaluationContext
from openfeature.flag_evaluation import FlagValueType, FlagResolutionDetails
from openfeature.provider import AbstractProviderclass AsyncProvider(AbstractProvider, metaclass=ABCMeta):def resolve_boolean_details(self,flag_key: str,default_value: bool,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[bool]:raise RuntimeError("Not allow calling sync method in AsyncProvider")@abstractmethodasync def resolve_boolean_details_async(self,flag_key: str,default_value: bool,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[bool]:passdef resolve_string_details(self,flag_key: str,default_value: str,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[str]:raise RuntimeError("Not allow calling sync method in AsyncProvider")@abstractmethodasync def resolve_string_details_async(self,flag_key: str,default_value: str,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[str]:passdef resolve_integer_details(self,flag_key: str,default_value: int,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[int]:raise RuntimeError("Not allow calling sync method in AsyncProvider")@abstractmethodasync def resolve_integer_details_async(self,flag_key: str,default_value: int,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[int]:passdef resolve_float_details(self,flag_key: str,default_value: float,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[float]:raise RuntimeError("Not allow calling sync method in AsyncProvider")@abstractmethodasync def resolve_float_details_async(self,flag_key: str,default_value: float,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[float]:passdef resolve_object_details(self,flag_key: str,default_value: typing.Union[Sequence[FlagValueType], typing.Mapping[str, FlagValueType]],evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[typing.Union[Sequence[FlagValueType], typing.Mapping[str, FlagValueType]]]:raise RuntimeError("Not allow calling sync method in AsyncProvider")provider.py
import typingfrom openfeature.evaluation_context import EvaluationContext
from openfeature.flag_evaluation import FlagResolutionDetails
from openfeature.provider import Metadatafrom open_feature_util import AsyncProviderclass MyProvider(AsyncProvider):def get_metadata(self) -> Metadata:return Metadata(name="my_provider")async def resolve_boolean_details_async(self,flag_key: str,default_value: bool,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[bool]:tenant_id = evaluation_context.attributes.get("tenant_id")user_id = evaluation_context.attributes.get("user_id")if flag_key.startswith("cross_domain_transfer_domain_"):domain = flag_key.split("_", )[-1]# todo 查询业务规则# 使用规则评估flag，假定目前只开放 租户id 为 1 的用户id 为 1、2、3 的用户可以进行 A、B、C 域的功能，其他均关闭if not tenant_id or not user_id or tenant_id not in (1,) or user_id not in (1, 2, 3):return FlagResolutionDetails(value=False, error_message="该功能暂未开放或您暂未被授权体验~")if domain not in ("A", "B", "C"):return FlagResolutionDetails(value=False,error_message=f"账户域（{domain}）转账功能暂未开放或您暂未被授权体验~")else:return FlagResolutionDetails(value=False, error_message="无此功能~")return FlagResolutionDetails(value=True)async def resolve_string_details_async(self,flag_key: str,default_value: str,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[str]:passasync def resolve_integer_details_async(self,flag_key: str,default_value: int,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[int]:passasync def resolve_float_details_async(self,flag_key: str,default_value: float,evaluation_context: typing.Optional[EvaluationContext] = None,) -> FlagResolutionDetails[float]:passmain.py
import decimal
from contextlib import asynccontextmanager
from dataclasses import asdict
from typing import Listimport uvicorn
from fastapi import FastAPI, Depends, Header, Body, Request
from openfeature import api
from openfeature.evaluation_context import EvaluationContext
from openfeature.flag_evaluation import FlagEvaluationDetails
from pydantic import BaseModel, Field
from starlette.responses import JSONResponsefrom provider import MyProvider@asynccontextmanager
async def lifespan(application: FastAPI):# 注册 Providerapi.set_provider(MyProvider())yieldapp = FastAPI(lifespan=lifespan)class FlagEvaluationException(Exception):pass@app.exception_handler(FlagEvaluationException)
async def flag_disabled_handler(request: Request, exc: FlagEvaluationException):return JSONResponse(content={"ok": False, "msg": str(exc)})class Transfer(BaseModel):demain: str = Field(..., description="账户域，A、B、C")account_id: str = Field(..., description="账户ID")amount: decimal.Decimal = Field(..., description="转账金额")operation: str = Field(..., description="操作类型，in-转入，out-转出")class Transaction(BaseModel):tx_id: str = Field(..., description="Transaction id")transfers: List[Transfer] = Field(..., description="List of transaction transfers")async def get_of_client():return api.get_client()async def check_by_flag(tenant_id: int = Header(..., alias="X-Tenant"),user_id: int = Header(..., alias="X-User"),raw: Transaction = Body(...),of_client=Depends(get_of_client),
) -> Transaction:ec = EvaluationContext(attributes={"tenant_id": tenant_id, "user_id": user_id})for tr in raw.transfers:flag_key = f"cross_domain_transfer_domain_{tr.demain}"detail: FlagEvaluationDetails[bool] = await of_client.get_boolean_details_async(flag_key, default_value=False, evaluation_context=ec)if not detail.value:raise FlagEvaluationException(detail.error_message)return raw@app.post("/cross_domain_transfer")
async def transfer(tenant_id: int = Header(..., alias="X-Tenant"),user_id: int = Header(..., alias="X-User"),transaction: Transaction = Depends(check_by_flag),
):# TODO: 真正转账逻辑print(tenant_id, user_id, transaction.transfers)return {"ok": True, "msg": "成功"}@app.post("/feature_flags")
async def transfer(tenant_id: int = Header(..., alias="X-Tenant"),user_id: int = Header(..., alias="X-User"),flags: list[str] = Body(...),of_client=Depends(get_of_client),
):flag_res = {}ec = EvaluationContext(attributes={"tenant_id": tenant_id, "user_id": user_id})for flag in flags:detail: FlagEvaluationDetails[bool] = await of_client.get_boolean_details_async(flag, default_value=False, evaluation_context=ec)flag_res[flag] = asdict(detail)return {"ok": True, "msg": "成功", "res": flag_res}if __name__ == '__main__':uvicorn.run(app, host="0.0.0.0", port=8000, log_level="debug", use_colors=True)POST 127.0.0.1:8000/cross_domain_transfer
X-Tenant 1
X-User 2
{"tx_id": "1234567890","transfers": [{"demain": "A","account_id": "1246","amount": "6666","operation": "out"},{"demain": "B","account_id": "345345","amount": "6600","operation": "in"},{"demain": "D","account_id": "23423","amount": "66","operation": "in"}]
}
POST 127.0.0.1:8000/feature_flags
X-Tenant 1
X-User 2
["sdf"]