IIS部署Flask服务导入IPython遇underlying buffer has been detached错误求助

问题场景 #

在IIS上部署Flask服务后，只要代码中包含import IPython语句就会报错，换用IPython 5.0、6.0、7.16.3版本均无法解决。但通过CMD直接运行代码可以正常启动本地服务器。

环境配置 #

python 3.6

Flask==1.1.2
Keras==2.1.3
scikit-learn==0.23.2
scipy==1.4.1
tensorflow==1.14.0
wfastcgi==3.0.0

示例代码 #

from flask import Flask
import IPython

app = Flask(__name__)

@app.route("/flaskapi2/")
def hello():
    return "Hello from FastCGI via IIS!"
if __name__ == "__main__":
    app.run()

错误信息 #

Error occurred while reading WSGI handler:

Traceback (most recent call last):
  File "E:\deploy_car_damage\wfastcgi.py", line 791, in main
    env, handler = read_wsgi_handler(response.physical_path)
  File "E:\deploy_car_damage\wfastcgi.py", line 633, in read_wsgi_handler
    handler = get_wsgi_handler(os.getenv("WSGI_HANDLER"))
  File "E:\deploy_car_damage\wfastcgi.py", line 600, in get_wsgi_handler
    handler = __import__(module_name, fromlist=[name_list[0][0]])
  File ".\main.py", line 2, in <module>
    import IPython
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\__init__.py", line 56, in <module>
    from .terminal.embed import embed
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\terminal\embed.py", line 15, in <module>
    from IPython.core.interactiveshell import DummyMod, InteractiveShell
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\core\interactiveshell.py", line 63, in <module>
    from IPython.utils import io
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\utils\io.py", line 94, in <module>
    stdin = IOStream(sys.stdin, fallback=devnull)
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\utils\io.py", line 38, in __init__
    for meth in filter(clone, dir(stream)):
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\utils\io.py", line 37, in clone
    return not hasattr(self, meth) and not meth.startswith('_')
  File "E:\deploy_car_damage\venv36\lib\site-packages\IPython\utils\io.py", line 81, in closed
    return self.stream.closed
ValueError: underlying buffer has been detached

StdOut: 

StdErr: 

错误含义解释 #

underlying buffer has been detached表示IPython初始化过程中尝试访问sys.stdin（标准输入流）的缓冲区，但在IIS通过wfastcgi托管的服务环境中，标准输入流的缓冲区已经被分离。IPython是为交互式终端设计的，依赖可交互的标准输入，但CGI模式下的服务环境没有交互式输入流，导致IPython无法正常初始化。

解决方法 #

方法一：直接移除IPython导入 #

IPython仅用于交互式调试，在IIS托管的生产服务环境中完全不需要。直接删掉代码中的import IPython语句即可解决问题。

方法二：条件导入IPython（保留本地调试功能） #

如果需要在本地运行时保留IPython的调试功能，同时避免IIS环境报错，可以通过条件判断只在本地启动时导入IPython：

from flask import Flask

app = Flask(__name__)

@app.route("/flaskapi2/")
def hello():
    return "Hello from FastCGI via IIS!"

if __name__ == "__main__":
    # 仅本地启动时导入并使用IPython
    import IPython
    # 这里可以添加IPython相关的调试代码
    app.run()

内容的提问来源于stack exchange，提问作者Mogli141