Flask doesn't render html page from docker [duplicate]-CodePudding

I have a simple flask app that works without docker but doesn't reply when being wrapped in docker container. I suspect I have some addresses messed up

from flask import Flask, render_template, request
import pandas as pd

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def uploadfile():
    if request.method == 'POST':  # check if the method is post
        df = pd.read_json(request.files.get('file'))
        return render_template('upload.html',  tables=[df.head().to_html(classes='data', header="true")])
    return render_template('upload.html')


if __name__ == '__main__':
    app.run(debug=True, port=5000)  # running the flask app

upload.html

<!doctype html>
<html>
  <head>
    <title>File Upload</title>
  </head>
  <body>
    <h1>File Upload</h1>
    <form 
      method="POST" 
      action="/" 
      enctype="multipart/form-data"
    >
      <p><input type="file" name="file"></p>
      <p><input type="submit" value="Submit"></p>
    </form>
    {% for table in tables %}
            {{ table|safe }}
    {% endfor %}
  </body>
</html>

The project tree:

├── script.py
├── templates
    └── upload.html

Dockerfile:

FROM python:3.7-slim-buster

WORKDIR /app

COPY requirements.txt ./


RUN apt-get update 
RUN pip install --no-cache-dir -r requirements.txt


RUN mkdir /templates

COPY script.py /app/
COPY ./templates/ /app/templates/

RUN dir

CMD [ "python", "script.py" ]

and I launch the docker image as

docker run -it --rm -p 5000:5000 online-app

The the logs are as follows:

* Serving Flask app "script" (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
 * Running on http://127.0.0.1:5000/ (Press CTRL C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 416-968-407

I go to the http://127.0.0.1:5000/ and the page is loading forever. What did I miss?

UPD: Using app.run(debug=True, host=0.0.0.0, port=5000) # running the flask app has logs like:

 * Running on http://172.17.0.2:5000/ (Press CTRL C to quit)

But the link is dead as well

CodePudding user response：

change listening host IP to 0.0.0.0

app.run(debug=True, host='0.0.0.0', port=5000)  # running the flask app

When you trying to connect to http://127.0.0.1:5000 - you trying to connect to localhost interface of your physical server (docker host) But flask application listening only inside-container's localhost, what is not accessible outside container

CodePudding user response：

I'm no expert with Flask especially, but according to your logs, it does not seem to listen on the correct address. Indeed, inside a container, 127.0.0.1 will not match with requests coming from outside the container (it would work with a Curl from inside the container for instance). In order to make it listen to "non-local" (as in "not originating from the container itself") requests, it has to listen on 0.0.0.0