Dockable

This is a gem that helps us with getting a common setup for our Ruby apps.

Features:

• Load environment variables from S3.
• Execute commands from a Procfile.

At Teachable, this gem is preinstalled on our Docker base images that have Ruby.

Dockable is a prefix to commands just like "bundle exec" or "time".

Say you have the following Procfile:

web: bundle exec puma -c config/puma.rb
worker: bundle exec sidekiq -C config/sidekiq.yml
release: bundle exec rake release

You can run puma like this:

$ dockable web

If you've added DOCKABLE_ENV_SSM_PREFIX as an environment variable, dockable will look for all values in the AWS Parameter store that begin with that prefix and load them as environment variables.

For instance, if I had /production/staff set as my DOCKABLE_ENV_SSM_Prefix and had the parameter /production/staff/follower_database_url set with the value postgres://funtime.com, dockable will load that as FOLLOWER_DATABASE_URL=postgres://funtime.com

Please Note: setting DOCKABLE_ENV_SSM_PREFIX will take precendence over loading environment variables from S3

If you've specified the DOCKABLE_ENV_BUCKET_NAME and DOCKABLE_ENV_KEY_NAME variables, it will try to download an environment file from that location.

That environment file is a yaml file, like this:

RAILS_ENV: production
DATABASE_URL: postgres://...
SECRET_KEY_BASE: deadbeef1234...

The reason we do it this way is so we don't have to configure so many environment variables when booting a Docker image.

The values of DOCKABLE_ENV_BUCKET_NAME would be something like "teachable-secrets" and the value of DOCKABLE_ENV_KEY_NAME would be "name-of-app/production.yml".

Make sure the bucket you store these environment variables in is private, but readable for your docker image, and uses encryption.

You can use dockable as an ENTRYPOINT option in your Dockerfile.

RUN gem install dockable
ENTRYPOINT ["dockable"]

If the command is not available in your Procfile, it will simply be executed.

$ dockable ls -alh

Protip: to check if environments are loaded, try running dockable env.

If DOCKABLE_ROOT_DIR is set, it will change the working directory.

You can change the location of the Procfile with DOCKABLE_PROCFILE_LOCATION

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/iain/dockable.