Docker Compose¶
Linux containers and Docker are radically changing the way that applications are developed, built, distributed and deployed. The AtoM team is experimenting with new workflows that make use of containers. This document introduces our new development workflow based on Docker and Docker Compose. The latter is a tool that help us to run multi-container applications like AtoM and it is suitable for both development and production environments.
If this is the first time that you have heard about containers you may find The New Stack eBook Series a useful resource to get up to speed quickly.
Install Docker and Docker Compose¶
Docker works the same whether you are using Docker for Windows, Docker for Mac or Docker on Linux. For the latter, make sure that both Docker Engine and Docker Compose are installed following the instructions in the links.
Spin it up¶
Let’s make sure that the Docker client can reach the engine. The following command will list the currently running containers:
docker ps
You should see an empty list. Now using git, check out the sources of AtoM and change your current directory.
git clone -b stable/2.3.x https://github.com/artefactual/atom.git atom
cd atom
Now set the environment variable COMPOSE_FILE to tell Compose what is the
location of our YAML file. You could do the same using the -f flag but we
don’t want to do so each time we invoke the docker-compose command.
# For bash users (most of you)
export COMPOSE_FILE="$PWD/docker/docker-compose.dev.yml"
# For fish users
set -lx COMPOSE_FILE (pwd)/docker/docker-compose.dev.yml
It’s time to use Docker Compose in order to provision our containers:
# Create and start containers. This may take a while the first time you run
# it because all the images have to be downloaded (e.g. percona, memcached)
# and the AtoM image has to be built.
docker-compose up -d
# Execute a command in the running container atom: purge database
docker-compose exec atom php symfony tools:purge --demo
# Execute another command: build stylesheets
docker-compose exec atom make -C plugins/arDominionPlugin
Tip
While you wait, take the opportunity to check out our Dockerfile, which describes the steps that are taken to build the AtoM image. It is based on Alpine Linux (only 2 MB) + PHP7 and the rest of dependencies. In addition, our docker-compose.dev.yml file shows how AtoM is orchestrated together with its service dependencies. It is an environment meant to be used by developers.
That’s it! You have started the containers and put them in the background, populated the database and compile the CSS stylesheet of the Dominion plugin. You can start developing right away. Changes made in the source code will take effect immediately.
Due to a bug that has not been solved yet, the AtoM worker needs to be restarted after the database is populated for the first time:
docker-compose restart atom_worker
Docker Compose lets you perform many different actions. Please refer to the documentation for more help. For example, you can monitor the output of some of your containers as follows:
docker-compose logs -f atom atom_worker nginx
You can also scale the cluster as needed. In the following example we are going to add extra AtoM workers and Elasticsearch nodes.
docker-compose scale atom_worker=2 elasticsearch=3
Let’s verify that the Elasticsearch cluster has indeed three nodes in place:
docker-compose exec atom curl elasticsearch:9200/_cat/nodes
cdec404af617 172.18.0.7 6 65 0.26 d m Huntara
366a7817864f 172.18.0.3 5 65 0.26 d * Vance Astro
0e52024208fe 172.18.0.6 4 65 0.26 d m Bloodstorm
You can also verify that two workers have subscribed to Gearman:
# Establish a TCP connection to gearmand, port 4730
docker-compose exec atom bash -c "nc gearmand 4730"
# Send STATUS command
STATUS
fdd4764376d2f763-arGenerateFindingAidJob 0 0 2
fdd4764376d2f763-arUpdatePublicationStatusJob 0 0 2
fdd4764376d2f763-arInformationObjectCsvExportJob 0 0 2
fdd4764376d2f763-arInheritRightsJob 0 0 2
You could temporarily stop all the services with docker-compose stop (which
will need docker-compose up -d later to start the services again) or both
stop and remove related containers, networks, images and volumes by running:
docker-compose down --volumes
Connect to AtoM¶
AtoM should be now accessible from your browser. If you want to find the address run the following:
$ docker-compose ps
Name Command State Ports
-------------------------------------------------------------------------------------------
docker_atom_1 /atom/src/docker/entrypoin ... Up
docker_atom_worker_1 /atom/src/docker/entrypoin ... Up
docker_elasticsearch_1 /docker-entrypoint.sh bash ... Up
docker_gearmand_1 gearmand --queue-type=libm ... Up
docker_memcached_1 /entrypoint.sh -p 11211 -m ... Up
docker_nginx_1 nginx -g daemon off; Up 192.168.64.2:8000->80/tcp
docker_percona_1 /docker-entrypoint.sh mysqld Up
As you can see in the right column, Nginx has published a TCP port. It may be different in your environment. In this example, we will put the following address in our browser: http://192.168.64.2:8000.
The default login details are:
- Username:
demo@example.com - Password:
demo
Please be aware that this process is new and it may have some unknown issues. Let us know if you have some feedback!
In case you have any doubts, we’ve prepared a recording of the terminal session: