docker_flask_homework

This assignment aims to provide hands-on experience in Dockerizing Flask applications, first individually and then using Docker Compose for managing multiple applications.

Part One: Dockerizing a Single Flask Application

Setting Up and Dockerizing a Flask App:

I used my previous Flask App for the base.html file and added in new things for the contactus.html file.

I first created a Dockerfile that contains the following:

FROM python:3.7-alpine
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD ["python", "app.py"]

Then I created an app.py file
Lastly, I created a requirements.txt file with flask in it

To Dockerize my FLask Application, I did the following steps:

First build the docker image with docker build -t <name> .
Then do docker images to show the docker images. Make sure your <name> is there.
Then run the command with docker run -d -p 5001:5000 <name>
Type in docker ps to check your docker container information.
When you are done with your Docker image, you can stop the image from running with docker stop <container ID>
If needed, you can delete images with docker system prune -a -f

Importance of each step in the Dockerfile:

FROM specifies which base operating system from the hub.docker.com with python installed in it
WORKDIR folder that houses this code
COPY copies the content of the current directory of the Dockerfile into the app directory within the container
RUN requirements.txt is to just install the python dependencies in requirements.txt (flask)
EXPOSE 5000 is to show that the docker container will be designed to listen on port 5000
CMD is to run the app.py through python when the container starts to run

Part Two: Multi-Container Setup with Docker Compose:

Prepare Two Flask Applications:

I created two folders under the Part2 Folder for the two flask applications: flask1 and flask2

In each folder contains:

Dockerfile that contains:

FROM python:3.10-slim-buster
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
EXPOSE 5000
CMD ["python", "app.py"]

app.py file
requirements.txt file with flask in it
templates folder for HTML

In the Part2 Folder, I have a docker-compose.yml file that contains:

version: '3'
services:
  flask_app_1:
    build: ./flask1
    ports:
      - "7000:5000"
    volumes:
      - ./flask1:/app
  flask_app_2:
    build: ./flask2
    ports:
      - "5020:5000"
    volumes:
      - ./flask2:/app

Explanation of each section of the docker-compose.yml file:

version is the version of the Docker Compose file that is being used (we are using version 3)
services is the section with the different services/containers for this application
flask_app_1 is the first flask app
build: ./flask1 directs the image built to flask1's dockerfile
ports maps port 5000 from the conatiner to port 7000 for the host.
volumes any changes that occur in the local files will be brought to the container here (same concept for flask_app_2 as well)

To run this, I did the following steps:

Start off by building the images: docker-compose up --build
If i need to reconnect to it, I did docker-compose up
If you want to see a list of your containers, use docker-compose ps
If needed, you can stop it with docker-compose down

How is Docker Compose different from Docker?

Docker Compose helps orchestrate multiple containers without running each container separately while Docker will run individually. If you have multiple containers and you only use Docker alone, then you will need to start and command each container separately while Docker Compose contains a docker-compose.yml file that helps you run your entire application at the same time, making it easier for you to run and stop each application.

Challenges:

No challenges encountered.

Helzheng123 / docker_flask_homework