docker compose

By | September 15, 2020
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Compose is a tool for defining and running multiple containers at once. For example if you want to create a wordpress website with a MySql database you can do this very easily with compose.

Previously we learned that we could use docker files to define containers. With compose you use compose-yaml files to define your multi container environment.

Both Dockerfiles and compose-yaml files work hand in hand to create your containerized environment.

Set up folder to start your compose session

First create a directory to put your compose project in. This directory will contain everything your project requires but nothing more.

For this example we be using just a yaml file but later we will also use Dockerfiles to build our images.

Create a directory called mywordpress using mkdir mywordpress then enter your directory using cd mywordpress.

Next create a yaml file called docker-compose.yaml using touch docker-compose.yaml

YAML YAML YAML

YAML is an acronym that stands for “YAML Ain’t Markup Language”. This is recursive wordplay is weird but we programmers are weird anyway :).

It is a human readable data serialization language where consitent indentation is required. You can use any number of spaces to indent your Yaml as long as it is consistent :).

The Docker compose file below uses four and two space indentation. This file is used for configuring docker-compose.

Edit your yaml file using vim docker-compose.yaml and press i for insert. Copy and paste the text below and press esc and :wq to save.

version: '3.3'

services:
   db:
     image: mysql:5.7
     volumes:
       - db_data:/var/lib/mysql
     restart: always
     environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress

   wordpress:
     depends_on:
       - db
     image: wordpress:latest
     ports:
       - "8000:80"
     restart: always
     environment:
       WORDPRESS_DB_HOST: db:3306
       WORDPRESS_DB_USER: wordpress
       WORDPRESS_DB_PASSWORD: wordpress
       WORDPRESS_DB_NAME: wordpress
volumes:
    db_data: {}

Now, run docker-compose up -d to build the project.

docker-compose up -d
Creating network "mywordpress_default" with the default driver
Creating volume "mywordpress_db_data" with default driver
Pulling db (mysql:5.7)...
5.7: Pulling from library/mysql
d121f8d1c412: Already exists
f3cebc0b4691: Pull complete
1862755a0b37: Pull complete
489b44f3dbb4: Pull complete
690874f836db: Pull complete
baa8be383ffb: Pull complete
55356608b4ac: Pull complete
277d8f888368: Pull complete
21f2da6feb67: Pull complete
2c98f818bcb9: Pull complete
031b0a770162: Pull complete
Digest: sha256:14fd47ec8724954b63d1a236d2299b8da25c9bbb8eacc739bb88038d82da4919
Status: Downloaded newer image for mysql:5.7
Pulling wordpress (wordpress:latest)...
latest: Pulling from library/wordpress
d121f8d1c412: Already exists
58b3577b786a: Already exists
60538287851f: Already exists
c53ff72fe225: Already exists
79b018c8773f: Already exists
fbe3e00ac4b0: Already exists
ff35226e1df8: Already exists
ab3b1d46dd82: Already exists
b29cdd230d9a: Already exists
d466b05cf627: Already exists
771f930f6d23: Already exists
b89a2786f2a3: Already exists
c35594c34f69: Already exists
8e3c480bd8bf: Pull complete
2d3e26ca1157: Pull complete
cc0d53b93bc3: Pull complete
dbcd12305020: Pull complete
90356c70a472: Pull complete
ceb2ac363e49: Pull complete
202d7e2f6c6c: Pull complete
Digest: sha256:7b67b32c076e9463a804182e0356966829d5533184c5064e22a7b97686e2154b
Status: Downloaded newer image for wordpress:latest
Creating mywordpress_db_1 ... done
Creating mywordpress_wordpress_1 ... done

Now navigate to http://localhost:8000

Log in and you are in your wordpress site pretty cool!

More to learn

There is so many things you can do with compose. The following is a list of some of the common commands. To discover more you can find the Docker compose file reference here.

docker-compose up // will run the yaml file
docker-compose up -d // will detach the process
docker-compose logs // will show the logs
docker-compose ps // will list the running containers
docker-compose down //will stop the servers
docker-compose down --volumes //will stop the servers and delete the database and network it creates

Before we go use docker-compose down --volumes to shut everything down. Happy composing!

docker-compose down --volumes
Stopping mywordpress_wordpress_1 ... done
Stopping mywordpress_db_1        ... done
Removing mywordpress_wordpress_1 ... done
Removing mywordpress_db_1        ... done
Removing network mywordpress_default
Removing volume mywordpress_db_data