Web application using Python3 not working when Dockerized

Question

HelloWorld-1.py

app = Flask(__name__)
@app.route('/')
def printHelloWorld():
    print("+++++++++++++++++++++")
    print("+ HELLO WORLD-1 +")
    print("+++++++++++++++++++++")
    return '<h1>Bishwajit</h1>'
    # return '<h1>Hello %s!<h1>' %name

if name == '__main__':
    app.run(debug='true')

Dockerfile

FROM python:3
ADD HelloWorld-1.py /HelloWorld-1.py
RUN pip install flask
EXPOSE 80
CMD [ "python", "/HelloWorld-1.py"]

Building docker using the below command

docker build -t helloworld .

Running docker image using below command

docker run -d --name helloworld -p 80:80 helloworld

when i run the below command

docker ps -a

i get the below output

CONTAINER ID  IMAGE      COMMAND               CREATED             STATUS             PORTS               NAMES

cebfe8a22493 helloworld "python /home/HelloW…" 2 minutes ago Up 2 minutes (unhealthy) 0.0.0.0:80->80/tcp helloworld

If I hit in the browser(127.0.0.1:5000), it does not give response, But when i run the python file individually, it runs properly in the browser.

you are trying to access by using 127.0.0.1:5000 so shouldn't the -p argument be as -p 5000:80? — Krishna Chaurasia
– Krishna Chaurasia, Commented May 30, 2021 at 6:16
i tried changing the port also, it did not work. Is my docker file correct? — Bishwajit Vikram
– Bishwajit Vikram, Commented May 30, 2021 at 6:32
i tried with that too.. In Dockerfile....it is there EXPOSE 80, should it be changed. — Bishwajit Vikram
– Bishwajit Vikram, Commented May 30, 2021 at 7:26
@programandoconro Finally it worked. I changed few things like ``` app.run(debug='true', port='5000', host='0.0.0.0') ``` ``` docker run -p 5000:5000 helloworld ``` — Bishwajit Vikram
– Bishwajit Vikram, Commented May 30, 2021 at 17:46

programandoconro · Accepted Answer · 2021-05-31 03:51:22Z

1

I reproduced your problem and there were four main problems:

Not importing flask.
Using name instead of __name__
Not assigning the correct port.
Not assigning the host.

This is how your HelloWorld-1.py should look like:

from flask import Flask
app = Flask(__name__)
@app.route('/')
def printHelloWorld():
    print("+++++++++++++++++++++")
    print("+ HELLO WORLD-1 +")
    print("+++++++++++++++++++++")
    return '<h1>Bishwajit</h1>'
    # return '<h1>Hello %s!<h1>' %name

if __name__ == '__main__':
    app.run(host='0.0.0.0')

This is how you Dockerfile should look like:

FROM python:3
ADD HelloWorld-1.py .
RUN pip install flask
CMD [ "python", "/HelloWorld-1.py"]

Then simply build and run:

docker build . -t helloflask
docker run -dit -p 5000:5000 helloflask

Now go to localhost:5000 and it should work.

Additionally: You could actually assign any other port, for example 4444, and then go to localhost:4444:

docker run -dit -p 4444:5000 helloflask

edited May 31, 2021 at 3:51

answered May 30, 2021 at 6:16

programandoconro

2,7792 gold badges24 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Bishwajit Vikram Over a year ago

In Dockerfile....it is there EXPOSE 80, should it be changed.

Bishwajit Vikram Over a year ago

Yes. correct .. If at all i want to expose a port, it need to first give the port, and expose it in Dockerfile.

Collectives™ on Stack Overflow

Web application using Python3 not working when Dockerized

HelloWorld-1.py

Dockerfile

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

HelloWorld-1.py

Dockerfile

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related