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Capistrano - Docker strategy deployment

This gem allows you to easily deploy applications based on Docker images. It allows you to deploy apps two ways:

1. Using default docker strategy (build, run etc)
2. Using docker-compose strategy


To get started you need to have:

1. A project with existing Dockerfile
2. A capistrano >= 3.3 version already hooked to your project

First - add following file to your gemfile:

gem 'capistrano-docker', github: 'netguru/capistrano-docker'

Next, add following to your Capfile:

require 'capistrano/docker'

If you want to deploy via docker strategy only on a specific stage, you can include these tasks only to a specific stage, like:

task :docker do
  require 'capistrano/docker'

task 'staging' => [:docker]

This will loadup docker tasks only in staging stage.

There are additional tasks available, which are run once in a seperate container, using configured links / volumes. Add them to Capfile as well if you want to use them. The tasks are:

require 'capistrano/docker/assets' - precompile assets
require 'capistrano/docker/migration' - run db:migrate
require 'capistrano/docker/npm' - run npm install
require 'capistrano/docker/bower' - run bower install

Next, optionally, specify the options in your config/stage/deploy.rb file, however the defaults provided should work out-of-the-box.

set :docker_current_container - the name of used container, defaults to: APPNAME_REVISION
set :docker_role - the name of the role which is used for Docker host, defaults to ':web'
set :docker_pull - related to building an image, should we always pull the baseimage, defaults to false
set :docker_dockerfile - specify the path to the Dockerfile (relative from project root directory), defaults to project root directory
set :docker_buildpath - the buildpath of the image, defaults to project root directory ( . )
set :docker_detach - should we detach when running the container (the '-d' option in docker run), defaults to true
set :docker_volumes - an array of volumes we want to hook up, defaults to empty
set :docker_restart_policy - specify the restart policy of the container, defaults to 'always', if nil given, no policy will be applied
set :docker_links - specify an array of links to other containers
set :docker_labels - specify an array of labels that can be added to a container at runtime, defaults to empty, however the label that is always added is:
set :docker_image - the name of the image that will be used, defaults to: APPNAME_STAGE
set :docker_image_full - name of the image with a tag, defaults to APPNAME_STAGE:REVISION
set :docker_additional_options - additional options that will be passed to the 'docker run' command, defaults to none
set :docker_copy_data - docker does not allow us to use symlinks so this is just a substitute for linked_files (and linked_dirs), however instead of linking it simply copy the contents, so these will be visible inside image
set :docker_cpu_quota - specify the value for --cpu-quota option when running containers (does not work with docker-compose)
set :docker_apparmor_profile - run docker containers with specified apparmor profile
set :docker_clean_before_run - stops and removes existing containers before running a new one (useful when running containers with -p option), defaults to false

set :docker_compose - should we use docker-compose strategy instead (note - all above options are obsolete using this option), using docker-compose requires you to have docker-compose.yml file in your root directory, defaults to false
set :docker_compose_path -> allow specify the path to the docker-compose.yml (see pull #5), defaults to nil
set :docker_compose_project_name - prefix for the container names, defaults to nil, so it defaults to the directory name the project is at
set :docker_compose_remove_after_stop - should we remove the containers after stopping them, defaults to true
set :docker_compose_remove_volumes - should we remove associated volumes with containers during their removal (rm -v option), default: true
set :docker_compose_build_services - specify services which should be built / ran with docker-compose (ex. docker-compose build web), default: none
set :docker_pass_env - the list of the environment variables that should be passed over to the docker-compose commands from command line (they are validated wether they exists before they are used) (ex: PULL_REQUEST_ID=10 cap staging docker:compose:start )
set :docker_assets_precompile_command - command to be executed as assets precompile task (when capistrano/docker/assets is used, defaults to 'rake assets:precompile')
set :docker_migrate_command - command to be executed as migration task (when capistrano/docker/migration is used, defaults to 'rake db:migrate')
set :docker_db_create_command - command to be executed as database creation task (use for first run deployments, defaults to 'rake db:create')
set :docker_npm_install_command - command to be executed for installing npm packages, defaults to 'npm install --production --no-spin'
set :docker_bower_install_command - command to be executed for intalling bower packages, defaults to 'bower install --production'

The docker tasks will attach themselves just after default deploy:updated task from capistrano.

Docker default strategy overview

Step-by-step what default strategy does:

1. prepares the build, copying over files and folders described in "docker_copy_data" option
2. builds the image based on the given Dockerfile, tagging it with "docker_full_image"
3. runs the containers based on built image, attaching volumes, links, labels etc
4. cleans previous containers - it finds previously running containers, stopping and removing them (images of those containers are not removed)
5. tags the new running container with :latest tag

Docker compose strategy overview

Using docker-compose strategy is a bit smaller and easier, however I would not recommend using this strategy on production, as docker-compose itself isn't production-ready

1. validate wether we passed over the environment variables described in "docker_pass_env"
2. it runs docker-compose up with project_name and detached options

Docker-compose strategy is not stopping the containers automatically. You can use the "docker:compose:stop" task to do that (just remember that this will remove any compose-created containers unless you change the "docker_compose_remove_after_stop" option)



  • Fix issue with default docker_compose_path value (#6)


  • New task available: docker:deploy:compose:down - it calls docker-compose down, not automated, but you can insert it manually, thanks @tcoenraad, see #4
  • New variable: docker_compose_path - allows you to specify the path to the docker-compose file (thx @Mossie93) see #5


Thanks to @JamesCarscadden you can specify you want to stop container before running new one (docker_clean_before_run option) and there is a new task docker:migration:create which will run rake db:create command (you can change it by changing docker_db_create_command)


#docker-compose Added option to specify service name to be built / ran if docker-compose file contains multiple environments. For example if you have services like:

    build: .

    build: .
    dockerfile: Dockerfile.staging

and you want to "run" only staging service, then add to deploy option: set :docker_compose_build_services, -> { "staging" }


#docker-compose Added option to specify wether we want to remove associated volumes when stopping / removing docker-compose containers, defaults to true


Added option to set cpu quota for containers (:docker_cpu_quota) - does not work with docker-compose


Added two additional tasks which can be ran just before container. Add to Capfile:

require 'capistrano/docker/npm' - for running npm install
require 'capistrano/docker/bower' - for running bower install


Two new tasks added that can be ran just before running a container: assets:precompile and db:migrate Add to Capfile:

require 'capistrano/docker/assets' - for asset task
require 'capistrano/docker/migration' - for migration task

See installation section for more info


You can add a custom apparmor profile that will apply to running new containers by setting docker_apparmor_profile variable


Docker compose now copies over docker_copy_data files to the release path before build


Docker compose now always rebuilds images before running them


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