Docker Compose Demo

This project provides a simplified demonstration of some basic docker compose functionality.

• Images
• Volumes
• Internal and external ports
• Automatic networking between containers
• Extending Docker Compose files for service reuse

The services consist of app2, a NodeJS application which can be run separately from its own compose file, and app1, a PHP application which calls app2 and runs under PHP-FPM. Both applications are proxied by nginx which runs in separate containers using the same image.

Getting started

Install Docker Compose.

Running app2

$ docker-compose -f docker-compose-app2.yml up -d

List the running containers; 8889 is the public port, denoted by 0.0.0.0:8889:

$ docker-compose -f docker-compose-app2.yml ps
          Name                    Command          State               Ports
----------------------------------------------------------------------------------------
dockercomposedemo_app2_1    node /app/app.js       Up      9001/tcp
dockercomposedemo_nginx_1   nginx -g daemon off;   Up      443/tcp, 0.0.0.0:8889->80/tcp

Follow the log output:

$ docker-compose -f docker-compose-app2.yml logs -f

Visit http://localhost:8889/app2/ in your browser; you should see the output of app2. In the terminal, you should see log output from nginx and NodeJs.

Make a change to the "hello world" output of ./app2/app.js and restart the app2 container:

$ docker-compose -f docker-compose-app2.yml restart app2

When you refresh your browser, the your change should appear. This is because the source of app2 is linked into the container as a volume. The restart is necessary to pick up the change because NodeJS only interprets your code on initial startup.

Stop and destroy app2:

$ docker-compose -f docker-compose-app2.yml down

Running app1

The default file name is docker-compose.yml, so we don't need to supply the -f parameter:

$ docker-compose up -d

List the running containers; 8888 is the public port for app1. Also note that app2's nginx is running on 8890, as redefined in ./docker-compose.yml, as opposed to its original 8889. Either way, each public port within a set of running containers must be unique or Docker will not allow them to start.

$ docker-compose -f ps
             Name                      Command          State               Ports
---------------------------------------------------------------------------------------------
dockercomposedemo_app1_1         php-fpm                Up      9000/tcp
dockercomposedemo_app2_1         node /app/app.js       Up      9001/tcp
dockercomposedemo_app2_nginx_1   nginx -g daemon off;   Up      443/tcp, 0.0.0.0:8890->80/tcp
dockercomposedemo_nginx_1        nginx -g daemon off;   Up      443/tcp, 0.0.0.0:8888->80/tcp

Note that there are two nginx containers running, both of which are instances of the same image which you can verify with docker ps.

Follow the log output:

$ docker-compose logs -f

In your browser, visit http://localhost:8888/app1/. You should see the output of app2 included below the output of app1. In your terminal, you should see log output from all four containers tracing the request through each.

Now, make a change to app1's output by editing ./app1/index.php. Refresh the browser and your changes will appear automatically since the source code is shared with the app1 container as a volume and PHP is interpreted per request.

Useful commands

Note that commands that reference a specific container (exec, for example) use the service names from the compose file. These are considerably easier to deal with than the actual docker container name, which will be something like "dockercomposedemo_nginx_1".

config

Config will show the "merged" version of your Docker Compose configuration, which is useful when dealing with compose files which extend each other.

$ docker-compose config

exec

Execute commands interactively in a running container; the following logs you into a shell on the nginx container.

$ docker-compose exec nginx sh

logs

Follow output for a specific container, if provided, or the whole group.

$ docker-compose logs -f nginx

Starting and stopping containers

Docker Compose supports various options for starting, stopping, and destroying containers which are wrappers around Docker's functionality. For simplicity during development, it's easiest to use docker-compose up and docker-compose down. The latter completely destroys the container, making it easy to return to a known good state.