问题出现：

在使用Vue3和Fastapi做前后端分离项目时，前端页面调用apisix网关再路由到后台fastapi的restfull接口 console报错：
Access to XMLHttpRequest at 'http://192.168.110.45:9080/retrieval_test_data_1030' from origin 'http://192.168.140.2:5100' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present  on the requested resource.​​​​​​

解决方法：

1）apisix的路由HTTP的方法需要添加支持OPTION选项

2）FastApi后台的服务需要添加CORSMiddleware

app = FastAPI()

#设置允许跨域
origins = [
    "http://192.168.110.45",
    "http://192.168.140.2",
    "http://192.168.110.45:9080",
    "http://192.168.140.2:5100",
    "http://192.168.110.45:5100",
]
# 后台api允许跨域
app.add_middleware(
    CORSMiddleware,
    allow_origins=origins , #这里可以填写["*"]，表示允许任意ip
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

@app.get('/')
async def index(request: Request):
    return templates.TemplateResponse("index.html", {"request": request})

if __name__ == '__main__':
    import uvicorn
    uvicorn.run(app="gui:app", port=5100, host="0.0.0.0", workers=3)

3）再次访问后正常。

更多解析请参考：https://www.cnblogs.com/AlvinLiang/p/15910902.html