How to "dockerize" Flask application? - python-2.7

Question

I have Flask application named as rest.py and I have dockerize but it is not running.
#!flask/bin/python
from flask import Flask, jsonify
app = Flask(__name__)
tasks = [
{
'id': 1,
'title': u'Buy groceries',
'description': u'Milk, Cheese, Pizza, Fruit, Tylenol',
'done': False
}
]
#app.route('/tasks', methods=['GET'])
def get_tasks():
return jsonify({'tasks': tasks})
if __name__ == '__main__':
app.run(debug=True)
Dockerfile is as follows
FROM ubuntu
RUN apt-get update -y
RUN apt-get install -y python-dev python-pip
COPY . /rest
WORKDIR /rest
RUN pip install -r Req.txt
ENTRYPOINT ["python"]
CMD ["rest.py"]
I have build it using this command...
$ docker build -t flask-sample-one:latest
...and when I run container...
$ docker run -d -p 5000:5000 flask-sample-one
returning the following output:
7d1ccd4a4471284127a5f4579427dd106df499e15b868f39fa0ebce84c494a42
What am I doing wrong?

Answer 1

The output you get is the container ID. Check with docker ps whether it keeps running.
Use docker logs [container-id] to figure out what's going on inside.
Some problems I can find in your question:
Change the app.run line to app.run(host='0.0.0.0', debug=True). From the point of view of the container, its services need to be externally available. So they need to run on the loopback interface, like you would run it if you'd set up a publicly available server on a host directly.
Make sure that Flask gets installed. Your docker image file requires all the commands to make it work from a blank Ubuntu installation.
Please do not forget to deactivate debug if you'd ever expose this service on your host. Debug mode in Flask makes it possible for visitors to run arbitrary code if they can trigger an exception (it's a feature, not a bug).
After that (and building the container again [1]), try curl http://127.0.0.1:5000/tasks on the host. Let me know if it works, if not there are other problems in your setup.
[1] You can improve the prototyping workflow with Flask's built-in reloader (which is enabled by default) if you use a volume mount in your docker container for the directory that contains your python files - this would allow you to change your script on the host, reload in the browser and directly see the result.

Answer 2

I believe that you need to reinforce your concepts about Docker, in order to understand how it works, and then you will achieve your objectives regarding "dockerizing" whatever application.
Here is an article which can give your some first steps.
An official HOWTO will also help you.
Some observations that might help you:
check if your Req.txt contains flask for installation
before dockerizing, check if your application is working
check your running containers with docker ps and see if your container is running
if it is running, test your application: curl http://127.0.0.1:5000/tasks
*
One more thing:
your JSON has an OBJECT with an ARRAY with just one ELEMENT
Is that what you want for your prototype?
Take a look on this doc, about the JSON standard.