Running a Flask app within a Docker container results in “./boot.sh: 2: exec: gunicorn: not found”

Question

I am trying to create a Flask app running within a Docker container but I have some complex dependencies so I am building from this image https://hub.docker.com/r/continuumio/anaconda/ .

I build the image (goes fine... environment works...) :

docker build -t my_image:latest .

Then try to run it

docker run --name my_image -p 80:5000 --rm my_image:latest

I get this error:

./boot.sh: 2: exec: gunicorn: not found

Here is my directory I am building from:

my_template
--api.py
--boot.sh
--environment.yml
--Dockerfile

I have a very simple flask app. api.py

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/', methods=['GET'])
def hello_world():
    return jsonify({'message': 'Hello World'})

@app.route('/test', methods=['GET'])
def test():
    return jsonify({'test': 'test'})

if __name__ == "__main__":
    app.run(debug=True) # remember to set debug to False

environment.yml is as follows:

name: ox
channels:
  - conda-forge
  - defaults
dependencies:
  {---OMITTED FOR BREVITY---}
prefix: /home/me/anaconda3/envs/ox

Dockerfile is as follows:

FROM continuumio/miniconda:latest

WORKDIR /home/conda_flask_docker

COPY environment.yml ./
COPY api.py ./
COPY boot.sh ./

RUN chmod +x boot.sh

RUN conda env create -f environment.yml

RUN echo "source activate ox" > ~/.bashrc
ENV PATH /opt/conda/envs/ox/bin:$PATH

EXPOSE 5000

ENTRYPOINT ["./boot.sh"]

And... boot.sh

#!/bin/sh
exec gunicorn -b :5000 --access-logfile - --error-logfile - api:app

Answer 1

Solved this on my own...

I needed to add

 - flask=1.1.2=pyh9f0ad1d_0 
 - gunicorn=20.0.4=py38h32f6830_1 

to the dependencies section of environment.yml. I had used conda env export > environment.yml to build my environment.yml BEFORE I had added Flask and gunicorn.

If that doesn't do it, adding gunicorn via RUN command in the Dockerfile should do.