Styjun

I have a problem running a little Flask app with Docker. Everything works fine with debug off, but when I try to run it with debug on it fails at the reloader stage. It works fine on Windows, the problem only comes up with Docker.

In my docker repo I install caffe and all the dependencies I need (flask and wekrzeug). I thought the problem could be with the reloader so I also installed watchdog but it still shows up. Doesn't matter whether I run app.py itself or call python -m flask run.

docker run --volume=%cd%:/workspace -p 5001:5000 caffe:cpu
 * Serving Flask app "app" (lazy loading)
 * Environment: production
 WARNING: Do not use the development server in a production environment.
 Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with inotify reloader
Traceback (most recent call last):
 File "app.py", line 53, in <module>
 app.run(debug = True, host='0.0.0.0')
 File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 943, in run
 run_simple(host, port, self, **options)
 File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 988, in run_simple
 run_with_reloader(inner, extra_files, reloader_interval, reloader_type)
 File "/usr/local/lib/python2.7/dist-packages/werkzeug/_reloader.py", line 332, in run_with_reloader
 sys.exit(reloader.restart_with_reloader())
 File "/usr/local/lib/python2.7/dist-packages/werkzeug/_reloader.py", line 176, in restart_with_reloader
 exit_code = subprocess.call(args, env=new_environ, close_fds=False)
 File "/usr/lib/python2.7/subprocess.py", line 523, in call
 return Popen(*popenargs, **kwargs).wait()
 File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
 errread, errwrite)
 File "/usr/lib/python2.7/subprocess.py", line 1343, in _execute_child
 raise child_exception
OSError: [Errno 2] No such file or directory

I've encountered the same problem here and the solution for me was to remove the executable flag from the "run.py" file.

$ chmod -x run.py

The error was very similar, but in my case I'm using an Ubuntu 18.04 WSL on a Windows 10 machine.

Try to run the app as a module:

python -m flask run

See https://github.com/pallets/flask/issues/1829 for more information.