Can't reach Flask server running in Docker container - docker

Question

I'm building a Flask + React webapp that runs correctly on my machine. I try to dockerize it. I can build image (stiko:demo), docker runs, server starts:
But when I try to open https://0.0.0.0:5000/ on my browser, connection fails:
I've searched for a while now, trying to start from various images, trying to use ENDPOINT + CMD command, use flask run --host=0.0.0.0 but still the same issue.
Here is Dockerfile:
FROM ubuntu:20.04
RUN useradd -ms /bin/bash ubuntu
RUN apt update
RUN apt install software-properties-common -y
RUN apt-get install libpq-dev -y
RUN add-apt-repository ppa:deadsnakes/ppa
RUN apt install python3.9 -y
RUN apt install python3-pip -y
RUN pip3 install --upgrade pip
WORKDIR /app/build
COPY ./build ./
WORKDIR /app/server
COPY ./server ./
RUN pip3 install -r requirements.txt --no-cache-dir
RUN pip3 install python-dotenv
ENV APP_SETTINGS="config.DevelopmentConfig"
EXPOSE 5000
app.py:
import sys
import os
from flask import Flask, request, render_template
from flask_sqlalchemy import SQLAlchemy
from flask_cors import CORS, cross_origin
from models import User, Project, Image, db
from api import blueprints
app = Flask(__name__,
static_folder='../build/static',
template_folder="../build"
)
app.config.from_object(os.environ['APP_SETTINGS'])
db.init_app(app)
cors = CORS(app)
# Register the blueprints
for b in blueprints:
app.register_blueprint(b)
#cross_origin
#app.route('/', defaults={'u_path': ''})
#app.route('/<path:u_path>')
def index(u_path=None):
return render_template("index.html")
if __name__ == "__main__":
app.run(host=('0.0.0.0'), port=5000, ssl_context='adhoc')
project structure:
build
|__static
|__index.html
|__ ...
server
|__app.py
|__requirements.txt
|__ ...
Dockerfile
Any help would be appreciated, thanks!

Answer 1

Your Dockerfile doesn't appear to be starting your flask api. Try adding a CMD to the end.
FROM ubuntu:20.04
RUN useradd -ms /bin/bash ubuntu
RUN apt update
RUN apt install software-properties-common -y
RUN apt-get install libpq-dev -y
RUN add-apt-repository ppa:deadsnakes/ppa
RUN apt install python3.9 -y
RUN apt install python3-pip -y
RUN pip3 install --upgrade pip
WORKDIR /app/build
COPY ./build ./
WORKDIR /app/server
COPY ./server ./
RUN pip3 install -r requirements.txt --no-cache-dir
RUN pip3 install python-dotenv
ENV APP_SETTINGS="config.DevelopmentConfig"
EXPOSE 5000
CMD [ "python", "app.py" ]

Answer 2

Well, just in case someone would be stuck like me, with probably zero network skill:
The Dockerfile and app.py are just fine. But instead of trying to access https://0.0.0.0:5000/ in browser I should have tried https://127.0.0.1:5000/ which works perfectly fine!