Python Flask Docker image

This tutorial provides a steps for building and deploying Python Flask demo project. Code repository - https://github.com/chandradeoarya/docker-flask

Docker image tags

Image name: chandradeoarya/hello-flask

Environment Variables

Variable	Required	Default	Description
`MYSQL_ROOT_PASSWORD`	Yes	Helloflask@1	mysql default password

Project directory structure

The following shows how to organize your project on the host operating system.

Basic structure

The following is the least required directory structure:

<project-dir>/
└── app.py              # Entrypoint file name can be changed via env var

Structure with dependencies

The following directory structure allows for auto-installing Python dependencies during startup into a virtual env.

<project-dir>/
├── app                      # Entrypoint dir name can be changed via env var
│   ├── __init__.py
│   └── main.py              # Entrypoint file name can be changed via env var
└── requirements.txt         # Optional: will pip install in virtual env

After you've started the container with a requirements.txt in place, a new venv/ directory will be added with you Python virtual env.

<project-dir>/
├── app
├── __init__.py
├── main.py
│   └── __pycache__
├── requirements.txt
└── venv
    ├── bin
    ├── include
    └── lib

Step-1 Building and running flask app image

For building the images you need to go inside your project directory hello-flask/ :

# Clone the repository if not done yet
git clone https://github.com/chandradeoarya/docker-flask.git

# Pull step-1 code
git pull origin master

docker build --tag hello-flask .

You can tag image builds based on versions:

docker tag hello-flask:latest hello-flask:v1
# to remove a tag
docker rmi hello-flask:v1

Now you have

docker tag hello-flask:latest hello-flask:v1

Run a container based on this image

docker run -d --name hello-flask-c --publish 5000:5000 hello-flask

Step-2 Adding mysql database in flask

We will use docker official image for MySQL and run it in a container. Before we run MySQL in a container, we’ll create a couple of volumes that Docker can manage to store our persistent data and configuration.

We are going to use volumes instead of bind mounts.

# Pull step-2 code
git pull origin step2

# Create docker volume
docker volume create hello-flask-mysql

# Create docker volume for mysql configurations
docker volume create hello-flask-mysql-config

Now we’ll create a network that our application and database will use to talk to each other. This will be a user-defined bridge network which gives a nice DNS lookup service which we can use when creating our connection string.

docker network create hello-flask-network

Now we can run MySQL in a container and attach to the volumes and network we created above. Docker pulls the image from Hub and runs it for you locally. In the following command, option -v is for starting the container with volumes. For more information, see Docker volumes.

 docker run --rm -d -v hello-flask-mysql:/var/lib/mysql \
  -v hello-flask-mysql-config:/etc/mysql -p 3306:3306 \
  --network hello-flask-network \
  --name helloflasksqldb \
  -e MYSQL_ROOT_PASSWORD=Helloflask@1 \
  mysql

Now, let’s test whether MySQL database is running and we can connect to it. Enter correct password when prompted:

docker exec -ti helloflasksqldb mysql -u root -p

Build docker image with mysql in flask

docker build --tag hello-flask-mysql .

#Run the new flask app with mysql
docker run --rm -d --network hello-flask-network --name hello-flask-mysql-c --publish 5000:5000 hello-flask-mysql

# Db connection test and getting table entries
curl http://localhost:5000
curl http://localhost:5000/initdb
curl http://localhost:5000/widgets

# Insert some data in mysql inventory.widgets table
docker exec -ti helloflasksqldb mysql -u root -p

insert into inventory.widgets (name, description) values ('flask','simple python webapi');
insert into inventory.widgets (name, description) values ('docker','best containerization tool');
insert into inventory.widgets (name, description) values ('mysql','best database service');

Step-3 Using Docker compose

# Pull step-3 code
git pull origin step3

# Docker compose up
docker-compose -f docker-compose.dev.yml up --build

License

MIT License