FastAPI优雅处理CORS跨域与日志记录的实战指南

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

app = FastAPI()

# 1. 定义允许的源列表
# 在生产环境中，请务必替换为具体的域名，而不是使用 "*" 通配符
# 例如: origins = ["https://your-frontend-domain.com"]
origins = [
    "http://localhost",
    "http://localhost:3000",
    "http://127.0.0.1",
    "http://127.0.0.1:3000",
]

# 2. 添加中间件
app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,           # 允许访问的源
    allow_credentials=True,          # 允许携带 Cookie
    allow_methods=["*"],             # 允许的方法 (GET, POST, PUT, DELETE, OPTIONS 等)
    allow_headers=["*"],             # 允许的请求头
)

@app.get("/")
async def root():
    return {"message": "Hello World with CORS enabled!"}

import logging
import sys

# 配置日志格式
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
    handlers=[
        logging.StreamHandler(sys.stdout)  # 输出到控制台
    ]
)

logger = logging.getLogger(__name__)

# 测试日志
logger.info("系统启动，日志配置已加载")

import time
from fastapi import Request
from starlette.middleware.base import BaseHTTPMiddleware

class LoggingMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        start_time = time.time()
        
        # 处理请求
        response = await call_next(request)
        
        # 计算耗时并记录
        process_time = (time.time() - start_time) * 1000  # 转换为毫秒
        formatted_time = f"{process_time:.2f}ms"
        
        logger.info(
            f"{request.method} {request.url.path} - "
            f"Status: {response.status_code} - "
            f"Duration: {formatted_time}"
        )
        
        return response

from fastapi import HTTPException, Request
from fastapi.responses import JSONResponse

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException):
    logger.error(f"HTTPException occurred: {exc.status_code} - {exc.detail} at {request.url.path}")
    return JSONResponse(
        status_code=exc.status_code,
        content={"detail": exc.detail},
    )

app = FastAPI()

# 添加 CORS (来自第二章)
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"], 
    allow_methods=["*"], 
    allow_headers=["*"]
)

# 添加日志中间件
app.add_middleware(LoggingMiddleware)

# ... 路由定义 ...

from logging.handlers import RotatingFileHandler

file_handler = RotatingFileHandler(
    "app.log", 
    maxBytes=10*1024*1024,  # 10MB
    backupCount=5,          # 保留5个旧文件
    encoding="utf-8"
)
file_handler.setFormatter(logging.Formatter("%(asctime)s - %(levelname)s - %(message)s"))
logger.addHandler(file_handler)

import logging
import time
import sys
from fastapi import FastAPI, Request, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse
from starlette.middleware.base import BaseHTTPMiddleware

# --- 配置区域 ---

# 1. 日志配置
logger = logging.getLogger("FastAPI_Prod")
logger.setLevel(logging.INFO)

# 控制台输出
console_handler = logging.StreamHandler(sys.stdout)
console_handler.setFormatter(logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s'))
logger.addHandler(console_handler)

# 文件输出 (可选，需确保目录存在)
# file_handler = RotatingFileHandler("logs/app.log", maxBytes=10000000, backupCount=5)
# file_handler.setFormatter(logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s'))
# logger.addHandler(file_handler)

# 2. CORS 配置
origins = [
    "http://localhost:3000",
    # 生产环境域名
    # "https://www.yourdomain.com"
]

# --- 中间件类 ---

class LoggingMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        start_time = time.time()
        response = await call_next(request)
        process_time = (time.time() - start_time) * 1000
        logger.info(f"{request.method} {request.url.path} - {response.status_code} - {process_time:.2f}ms")
        return response

# --- 应用初始化 ---

app = FastAPI(title="Production Ready API", version="1.0.0")

# 注册中间件（注意顺序：CORS 通常建议在较前的位置，但 Logging 可以包裹它）
app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)
app.add_middleware(LoggingMiddleware)

# --- 异常处理 ---

@app.exception_handler(Exception)
async def global_exception_handler(request: Request, exc: Exception):
    logger.error(f"Unhandled Exception: {exc}", exc_info=True)
    return JSONResponse(
        status_code=500,
        content={"detail": "Internal Server Error"},
    )

# --- 路由 ---

@app.get("/")
async def root():
    return {"message": "API is running with advanced logging and CORS"}

@app.get("/error")
async def trigger_error():
    # 触发一个异常来测试日志捕获
    raise HTTPException(status_code=400, detail="Bad Request Test")

# --- 启动命令 ---
# uvicorn main:app --reload