Error Installing Python 3 in Docker Container along with Mongo DB

I am trying to make a container where I install Mongo DB server as well as python 3.8 with pymongo module but it does not work. In the dumps folder I am trying to create a backup of tar.gz file of which will have volumes with the host machine using the code mongodump --archive=backup.tar.gz --gzip . How would I be able to change the code so that the container could be created and wont be faulty. How would I also be able to test if the backup is properly working?

Error when run docker-compose up --build:

#0 3.837 Reading state information...
#0 3.895 E: Unable to locate package python3.8
#0 3.895 E: Couldn't find any package by glob 'python3.8'
#0 3.895 E: Unable to locate package python3.8-dev
#0 3.895 E: Couldn't find any package by glob 'python3.8-dev'
#0 3.895 E: Couldn't find any package by regex 'python3.8-dev'

Dockerfile

FROM mongo:4.0.4

# Install Python 3.8
RUN apt-get update && \
    apt-get install -y python3.8 python3.8-dev python3-pip && \
    ln -s /usr/bin/python3.8 /usr/local/bin/python3

# Install pymongo
RUN pip3 install pymongo

EXPOSE 27017

# Create src and dump directories
RUN mkdir /app
VOLUME ["/app/src", "/app/dump", "/data/db", "/var/www/html"]

CMD ["/bin/bash"]

docker-compose.yml file:

version: '3.2'

services:
  py-mongo:
    build:
      context: .
      dockerfile: Dockerfile
    volumes:
      - ./src:/app/src
      - ./dump:/app/dump
      - ./mongo-data:/data/db
      - ./mongo-app:/var/www/html
    command: tail -f /dev/null
    environment:
      - MONGO_INITDB_ROOT_USERNAME=root
      - MONGO_INITDB_ROOT_PASSWORD=1234
    ports:
      - "27017:27017"

Tree Structure

.
├── Dockerfile
├── README.md
├── docker-compose.yaml
├── dump
├── mongo-app
├── mongo-data
└── src

The Docker images aim to be as small as possible. That's why they often do not include software we have in our workstations.

In the Mongo image there's no repository with python3.8 package for apt-get.

You have 2 options:

• Add a repository for apt-get
• Install Python from tgz file

Choose which is better for your purpose.

Adding the repository:

$ apt-get install software-properties-common
$ add-apt-repository ppa:deadsnakes/ppa

The Python installation:

$ apt-get update
$ apt-get install python3.8

will work then.

A Docker container is a wrapper around a single process. This backup task is running as a separate process and so it probably needs to run in a separate container. Conversely, this means you can just use the standard Docker Hub python image for your script, and the unmodified mongo image for the database.

FROM python:3.8
WORKDIR /app

# COPY requirements.txt ./
# RUN pip install -r requirements.txt
RUN pip install pymongo

COPY ./ ./
CMD ["./myscript.py"]

In the Compose file, you'd have separate containers for the database and script. You will need to pass along some connection information to both containers. I've specified these settings as environment variables; your code will need to get these settings back from os.environ.

version: '3.8'
services:
  db:
    image: mongo:4.0
    volumes:
      - ./mongo-data:/data/db
    environment:
      - MONGO_INITDB_ROOT_USERNAME=root
      - MONGO_INITDB_ROOT_PASSWORD=1234
    ports:
      - "27017:27017"
  script:
    build: .
    volumes:
      - ./dump:/app/dump
    environment:
      - MONGO_HOST=db
      - MONGO_USERNAME=root
      - MONGO_PASSWORD=1234

Now just running docker-compose up -d will start the whole thing. Notice that we've never specified an interactive shell as the main container command or used tail to "keep a container alive", and conversely, we don't need docker exec or to manually start processes inside running containers.

Your question has a very brief mention of an HTML directory. Whatever's serving this would go into a third container, again possibly built FROM python and including a server framework like Django or Flask in its requirements.txt file.