python - Flask App does not start with 0.0.0.0 host locally

Question

So, I created a sample Flask app, which I dockerized for our Kubernetes environment. But when I try to run my app locally, I get an Address already in use error. It's a very simple web server in Flask:

My app.py

if __name__ == "__main__":
    ENV = os.environ.get('env', INT)
    PORT = os.environ.get('flaskPort', PORT)
    logging.info(f" **** ENV={ENV} PORT={PORT} **** ")
    app.run(host="0.0.0.0", port=PORT, debug=True)

and here's the error I see when I run python3 src/app.py:

 * Serving Flask app "MOCK EHR FHIR SERVER" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: on
Traceback (most recent call last):
  File "/Users/x/git/mock-python-server/src/app.py", line 136, in <module>
    app.run(host="0.0.0.0", port=PORT, debug=True)
  File "/Users/x/git/mock-python-server/venv/lib/python3.9/site-packages/flask/app.py", line 990, in run
    run_simple(host, port, self, **options)
  File "/Users/x/git/mock-python-server/venv/lib/python3.9/site-packages/werkzeug/serving.py", line 1030, in run_simple
    s.bind(server_address)
OSError: [Errno 48] Address already in use

I don't have anything running on 5000. But, when I change the host to 127.0.0.1, it starts up just fine. Do I always have to change it to 127.0.0.1 when I run it from the cmd line and 0.0.0.0 when it's in a container?

question from:https://stackoverflow.com/questions/66054244/flask-app-does-not-start-with-0-0-0-0-host-locally

Answer 1

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