[SOLVED] Docker for Flask application is not running -connection error

Issue

I am running a Flask application in docker and I cannot get it started. I am working on Ubuntu 18.04.

What happens is that I build the image, I run and then I do in my browser at 127.0.0.1:5000 and get a connection error.

I build the image :

sudo docker build -t flask-image:latest .

Then I run:

sudo docker run -d -p 5000:5000 --name flask_try flask-image:latest

Now, when I go in a browser to 127.0.0.1:5000, the connection fails.

Then I do sudo docker ps and I get :

CONTAINER ID   IMAGE                COMMAND           CREATED         STATUS         PORTS                    NAMES
c161375d3a7a   flask-image:latest   "python app.py"   5 seconds ago   Up 4 seconds   0.0.0.0:5000->5000/tcp   flask_try

I did also :

sudo docker logs flask_try

Here I get some warnings related to a library I import, that is all. It seems to me that some warnings are not a problem. Does someone think otherwise ?

I did also :

sudo docker exec -it flask_try  /bin/bash

And I get the error "container is not running" :

Error response from daemon: Container b20b12ac58d461e5e60c5da1873585f03ba2c8c7a2c3d3408e4e46882e2f69d3 is not running

Here is what my Dockerfile looks like :

FROM python:3.7 as alias_one

RUN apt-get clean && apt-get update
RUN apt-get install -y \
    software-properties-common \
    python3.7 \
    python3-pip \
    wget \
    apt-transport-https \
    build-essential \
    ca-certificates \
    bash \
    perl \
    publicsuffix 

RUN mkdir /local/
WORKDIR /local/

(... install libs with wget, run installation shells etc. ...)

# second image:
FROM python:3.7

# new workdir
WORKDIR /flask_app_dir
ADD . /flask_app_dir

ARG SPACY_VERSION=2.3.4

COPY ./dir1 /flask_app_dir/dir1
COPY ./__init__.py /flask_app_dir/__init__.py
COPY ./config.py /flask_app_dir/config.py
COPY ./app.py /flask_app_dir/app.py


COPY ./requirements.txt /pynlg_root/requirements.txt

COPY --from=alias_one /local/ /local/

# I declare here a path I need
ENV PATH /local/bin:/local/cmd:$PATH

RUN pip install -r requirements.txt
RUN pip install spacy==${SPACY_VERSION}
RUN python -m spacy download fr_core_news_lg
RUN pip install six

ENTRYPOINT ["python"]
CMD ["app.py"]

The file requirements.txt contains one line :

flask==1.1.2

My application (file app.py) is this. Note: this Flask application works well without Docker.

# encoding: utf-8
from flask import Flask
app = Flask(__name__)

( ... imports ...)

@app.route('/', methods=['GET', 'POST'])
def parse_request():
    ( ... run some code that does something ...)
    return_dict = {
        "key1":"value1"
        "key2":"value2"
    }
    return return_dict

if __name__ == '__main_':
    app.run(debug=True, host='0.0.0.0', port=5000)   

Any help is welcome !

Solution

I solved my problem. In fact I had to delete from my Dockerfile:

ENTRYPOINT ["python"]
CMD ["app.py"]

And replace it just with :

CMD ["flask", "run", "--host", "0.0.0.0"]

This allowed to see the result in the browser.

Answered By - Catalina Chircu