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Continuous Integration and Deployment Pipelines with Flask, Docker and Github Actions

January 4, 2022

DevOps is the practices or stages that every application will go through before and after deployment in the industry. It ensures both continuous integration and deployment of the application by allowing a series of updates to the code repository.

The CI and CD pipelines are the set of practices used in the industry to develop and maintain every deployed application. Developing applications from the ground up requires so many practices and keeping track of every change to not break the already deployed application in the production.

GitHub Actions is an automation tool provided by Github that makes continuous integration very smooth and effortless.

In this article, we will experience building an interactive application.

Docker packages applications into images and stores them as containers with their configurations defined in the DockerFile.

Table of Contents

Prerequisites

To follow along with this tutorial, you should meet the following requirements.

  • An understanding of a GitHub repository and the Python programming language.
  • Python installed.
  • A pre-installed IDE, preferably Visual Studio Code.
  • An understanding of Docker.
  • A Docker Hub Account Docker Hub
  • An understanding of Flask.

Objectives

In this tutorial, we will be learning the continuous integration and deployment with Docker, Selenium, and GitHub actions. In addition, you will learn the following and apply them to the project:

  • Development and operations overview.
  • Creating a simple Flask application.
  • CI and CD Pipelines architecture.
  • Continuous Integration and deployment with Github Actions.
  • Docker images and container basics.

Development and operations overview

There are different stages involved in building pipelines, from development to production. These are the defined development and operations pipelines in the industry.

The picture below describes all the pre-defined stages.

DevOps Stages

Every industry begins the development of applications with the following set of practices:

Plan

Without a proper plan, no one can successfully develop an application. Therefore, we must put an adequate plan before embarking on the development journey. This is when we justify the tech stack and other required things.

Code

Developers embark on the coding part after the requirements have been set in the planning stage. Then, they will work on the application by collaborating through a single repository source.

Build

In this stage, the application developed shall be packaged and built into images using a package manager like Docker. We also ship the application into containers with the configurations file required for its start-up.

Test

A series of tests will run through the application for better performance. Tests like unit, integrating, etc., will be conducted during development.

The testers and quality assurance engineers can accomplish other tests. Several tools can do this, but the most popular is Selenium. The operation team does other stages, and they are as follows:

Release

This is where the stage of continuous integration begins. This stage will be repeated countless times whenever there is any update to the application. The popular tools used for this industry are Jenkins, GitHub Actions, Team City, and more.

Deploy

An application that passes the continuous integration stage will proceed to the deployment stage. Staging will be the first thing here before deployment using Ansible, Puppet or Chef.

Operate

The deployment will begin fully using tools like Terraform. The refined application will then be deployed and its operations monitored.

Monitor

The deployed application will be monitored in terms of performance. Logs will be generated while it’s been monitored. The most popular tools used in this regard and Selenium, Nagios, ELK etc.

An application undergoes all the above practices in the industry. A person skilled in all these is a DevOps Engineer.

Creating simple Flask application

Open your favorite code editor and navigate to the terminal. Run the following commands to set up your project workflow.

cd ~/Desktop
mkdir flaskdrinks
cd flaskdrinks
python3 -m venv env
source env/Scripts/activate
pip install flask
pip freeze > requirements.txt

You changed the directory to Desktop and then made a new directory called flaskdrinks. Every Python application requires a virtual environment with env being the file for this project.

Furthermore, you installed flask dependency with the python package manager called pip. You also tracked the dependencies with a file called requirements.txt.

Create a file called app.py and add the code snippet below;

from flask import Flask
from datetime import datetime
app = Flask(__name__)

data = {
    "drinks": [
        {
            "name": "Grape", 
            "description": "Delicious grape fruit drink",
            "date": datetime.now()
            },
            {
            "name": "Lemon", 
            "description": "Undiluted lemon fruit drink",
            "date": datetime.now()
            },
            {
            "name": "Mango", 
            "description": "This is a mango fruit",
            "date": datetime.now()
            }
        }
    ]
} 

@app.route("/")
def index():
        return "Welcome To My Drinks API"

@app.route('/drinks')
def get_drinks():
    return data


if __name__ == "__main__":
    app.debug = True
    app.run()

Now start the server with the command python app.py in the terminal. Open your browser to the root domain and confirm the welcome page. You can also route to /drinks and get the API data.

CI and CD Pipelines architecture

A continuous integration server is going to trigger the automated build test job. This is to check whether the pushed code is reliable or not. If the code is reliable, it will be integrated, built, and sent to the deployment server. Successful notifications will be sent, too, referred to as automation.

If not, the pushed codes would fail to build, and another notification would be sent. So that the developer can fix the bugs and then re-commit the code. The continuous integration tool will then start building the code again. This is why the continuous integration and deployment stages are still considered a waterfall model.

Continuous integration and deployment with Github Actions

Github Actions automates the build process whenever there is a push to the code repository. This helps to reduce the problem of a manual building of the jobs and always notify if the build is not complete.

This follows a workflow using a different language package file. Earlier, we cloned a Python application built with the Flask framework. Therefore, the workflow that we will define will be for the Python package.

Navigate to the repository and click on the action link. Then you should receive something similar to the image below.

Python Package

Now select the Publish Python Package and click on the Set up this workflow. You will then be redirected to the python-publish.yml editing page. Paste the workflow below and tap on start commit inside the editor.

name: Python Package

on:
    push:
      branches: [ master ]

jobs:
    deploy:
       runs-on: ubuntu-latest
       strategy:
         fail-fast: false
         matrix:
            python-version: [3.8]
       steps:
        - uses: actions/checkout@master
        - name: Initialize Python 3.7
          uses: actions/setup-python@v1
          with:
            python-version: ${{matrix.python-version}}
        - name: Install dependencies
          run: |
            python -m pip install --upgrade pip
            pip install -r requirements.txt

Every workflow package defined for the Github action has three major properties globally. They are the name, on and jobs. The name defines the tag given to the whole process, and this can be anything as far as it is meaningful.

The on property describes when the automation is going to start. According to the above workflow, at every code push into the repository, the actions will start building the code and then move on to the next step.

Now the jobs are what to be done at every step. We want to deploy on the ubuntu-latest machine in this workflow. Deploying the code requires the steps as defined. This step will start by installing some dependencies as described, and on successful build, you will have all the steps marked. Something like the image below;

Successful Build

Docker images and containers basics

The default way to deploy applications was to spin up a virtual machine in the past. This copies the necessary binaries’ artifact and the execution in the background.

In essence, a virtual machine is composed of a host operating system with the sets of default packages installed. The application will use the operating system files and resources to run successfully.

Additionally, the virtual machine provides the benefits of infrastructure through the hypervisor. This hypervisor allows many virtual machines to run and is also used to create them on the operating system.

However, the trade-off is the replication of the operating system. The more virtual machines run, the higher the space consumed in the host operating system. To optimize the backlog of this concept, the industry introduced the containerization of applications.

Containers are a lightweight and reliable technique to deliver a product to consumers while using available resources better.

Instead of having multiple virtual machines, we can have one hosting system that runs multiple containers. The processes in the containers are isolated, and they have access to the file system with packages on the host operating system.

The creation and execution of the containers are delegated to a container management tool such as Docker. This OS-level virtualization unlocks the benefits of running multiple applications by using the containers.

The following section will look at containerising applications using Docker and the Dockerfile dependency.

Create a Dockerfile inside the project folder and add the Docker commands below.

FROM python:3.8
WORKDIR /app
COPY . .
RUN pip install -r requirements.txt
ENV PORT=80

Furthermore, we have to build the Docker image and push it to the Docker hub for storage. But before that, create a new repository in the Docker hub that will store your Docker image from the build actions.

You will add your Docker hub account details to the GitHub secrets. You can do that by going to your GitHub account, clicking on the settings button, and tapping the secrets.

Add the following to the name and values:

DOCKER_USERNAME: <your-username>
DOCKER_PASSWORD: <your-password>
DOCKERHUB_REPO: <your-username>/<your-repository>

Having done all the steps above, navigate to the Github repository for the application, edit the workflow with the code below. This will build the Docker image and send it to your Docker hub repository.

name: Python Package

on:
    push:
      branches: [ master ]

jobs:
    deploy:
       runs-on: ubuntu-latest
       strategy:
         fail-fast: false
         matrix:
            python-version: [3.8]
       steps:
        - uses: actions/checkout@master
        - name: Initialize Python 3.8
          uses: actions/setup-python@v1
          with:
            python-version: ${{matrix.python-version}}
        - name: Install dependencies
          run: |
            python -m pip install --upgrade pip
            pip install -r requirements.txt
        - name: Check docker installed or not
          run: docker run hello-world
        - name: Push to docker hub
          uses: docker/build-push-action/@v1
          with:
            username: ${{secrets.DOCKER_USERNAME}}
            password: ${{secrets.DOCKER_PASSWORD}}
            repository: ${{secrets.DOCKERHUB_REPO}}
            tag_with_ref: true

Upon successful building of the Docker image, the following will be displayed on your screen;

Successful Docker image Build

Conclusion

In this tutorial, we saw the overview of DevOps and built an automated pipeline. Then, developed a simple Flask application and continuously integrated it with Github actions.

We went ahead to build its Docker image through these Github actions and then pushed it to the Docker hub for proper storage.

Happy coding!


Peer Review Contributions by: Geoffrey Mungai