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Last updated: 6 Apr 2021

Publish a Ruby gem


In general, the gem name should be the same as the thing you require when using it. This means using _, and not - to separate multi-word gem names. See the name your gem guide for more detailed guidance.

Also see the general policy on naming.


Follow the guidelines on for assigning version numbers.

Versions should only be changed in a commit of their own, in a pull request of their own.

This alerts team members to the new version and allows for last-minute scrutiny before the new version is released. Also, by raising a separate pull request, we avoid version number conflicts between feature branches.

File layout

We should follow the scheme used by Bundler when creating gems (see this railscast).


  • The version is stored in a file by itself in lib/<gem_name>/version.rb.
  • The Gemfile references the gemspec for gem dependencies. All gem dependencies should be specified in the gemspec.
  • The Gemfile.lock is never committed (it should be in the .gitignore file).

Releasing gem versions

The default Jenkins build script will automatically detect the presence of a gemspec file and publish the gem to See the Jenkinsfile for govuk_app_config for an example.

Clearing the gemstash cache

When a new gem version is released, it may not be available immediately on Jenkins. This is due to gemstash, our gem mirror. It caches versions for up to 30 minutes. To force it to clear, restart gemstash on the apt machine in the relevant environment, e.g. for integration:

gds govuk c ssh -e integration apt 'sudo docker restart gemstash'

To clear the cache for the CI Jenkins instance, run this in integration.