Practical examples

Python external program using docker MySQL

Create MySQL container

In this example, we'll work with user root.

• https://hub.docker.com/_/mysql

Create container with config

docker create -p3306:3306 --name myese -e MYSQL_ROOT_PASSWORD=toor mysql

Validate container creation

docker ps -a

Docker container created

Start container

docker start myese # or
docker start 0bd6cfe5a5e8

docker ps

Dockerr container started

We have our container running (:

Create a simple Python program to interact with MySQL

Install MySQL package

pip install mysql-connector-python

Connection to MySQL

This is our file, called myappa.py:

import mysql.connector

conn = mysql.connector.connect(user='root', password='toor', host='127.0.0.1')

conn.close()

List databases

import mysql.connector

conn = mysql.connector.connect(user='root', password='toor', host='127.0.0.1')
cursor = conn.cursor()

cursor.execute("SHOW DATABASES")

for database in cursor:
    print(database)

conn.close()

Databases

Create a database

import mysql.connector

conn = mysql.connector.connect(user='root', password='toor', host='127.0.0.1')
cursor = conn.cursor()

cursor.execute("CREATE DATABASE test")
cursor.execute("SHOW DATABASES")

for database in cursor:
    print(database)

conn.close()

Database 'test' created

Dockerize an external program

We'll take as example this code:

import mysql.connector

conn = mysql.connector.connect(user='root', password='toor', host='127.0.0.1')
cursor = conn.cursor()

cursor.execute("CREATE DATABASE test")
cursor.execute("SHOW DATABASES")

for database in cursor:
    print(database)

conn.close()

To dockerize that, we need a Dockerfile file, in this case, we will have this content in it:

FROM python:3.12.2

RUN mkdir -p /home/app

COPY requirements.txt /home/app/requirements.txt
RUN pip3 install -r /home/app/requirements.txt

COPY . /home/app

EXPOSE 5000

CMD ["python3", "/home/app/myappa.py"]

And inside requirements.txt file, the list of our packages:

mysql-connector-python

Now, using the next command, we could create the image related to our program:

# docker build -t [custom_name]:[custom_tag] [route_Dockerfile]
docker build -t miapp:1 .

Finally, if everything is okay, we will see the image created:

❯ docker images
REPOSITORY   TAG       IMAGE ID       CREATED          SIZE
miapp        1         309ed83e6e7e   13 seconds ago   1.12GB

But this is not doing anything, because our image is connecting to host 127.0.0.1 of a MySQL container, but to connect containers we need a little more of knowledge.

Well, to make things work, we need to use networks.

Connection between dockers containers

We need to use networks, with it container can talk between them:

docker network create mired

Now create the MySQL container:

docker pull mysql
docker create -p3306:3306 --name testdbs --network mired -e MYSQL_ROOT_PASSWORD=toor mysql

Now, create container of our app:

To this, change the host in our program:

• Instead of 127.0.0.1, we need to use the name of the container where (in this case) MySQL is running, so, host is now the name of that container.

import mysql.connector

conn = mysql.connector.connect(user='root', password='toor', host='testdbs')
cursor = conn.cursor()

cursor.execute("CREATE DATABASE test")
print("Base de datos test creada")

print("Lista de bases de datos:")
cursor.execute("SHOW DATABASES")

for database in cursor:
    print(database)

conn.close()

And the Dockerfile:

FROM python:3.12.2

RUN mkdir -p /home/app

COPY requirements.txt /home/app/requirements.txt
RUN pip3 install -r /home/app/requirements.txt

COPY . /home/app

EXPOSE 5000

CMD ["python3", "/home/app/myappa.py"]

docker build -t miapp:1 .

docker create -p5000:5000 --name testmipyapp --network mired miapp:1

And these are our containers:

CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS    PORTS     NAMES
a5f4610877d4   miapp:1   "python3 /home/app/m…"   2 seconds ago   Created             testmipyapp
89fea610bee4   mysql     "docker-entrypoint.s…"   6 minutes ago   Created             testdbs

First, start MySQL container:

docker start testdbs

Then, our app:

docker start testmipyapp

If we see the container logs of our program, we'll notice that execution was success:

docker logs testmipyapp

Base de datos test creada
Lista de bases de datos:
('information_schema',)
('mysql',)
('performance_schema',)
('sys',)
('test',)

If you are having an error in the connection to the MySQL container, try start your app after some seconds, or check logs of MySQL container to know when the container is fully running.

Our containers are talking to each other, using networks (: