KubernetesTemplateRendering

The invoca-kubernetes_template gem is a thin wrapper around jsonnet and erb to allow for the generation of Kubernetes manifests from a set of templates combined with a definitions.yaml file which stores environmental configuration for various deployment environments.

Install the gem and add to the application's Gemfile by executing:

bundle add kubernetes_template_rendering

If bundler is not being used to manage dependencies, install the gem by executing:

gem install kubernetes_template_rendering

This gem is meant to be used as a command line tool for rendering templates that are either written in jsonnet or erb. To use this gem you can either install it, and use the render_kubernetes_template executable directly, or you can use gem exec to execute the command without first installing the gem.

gem exec -g kubernetes_template_rendering render_templates \
    --jsonnet-library-path deployment/vendor \
    --rendered-directory path/to/resources \
    deployment/templates

To see a full list of options and how to use them, run the following command:

gem exec -g kubernetes_template_rendering render_templates --help

Pass --only NAME (repeatable) to render only the definitions.yaml entries whose top-level key exactly matches NAME. Composes with --cluster_type/--region/--color/--spp — all filters are AND'd.

gem exec -g kubernetes_template_rendering render_templates \
    --rendered-directory path/to/resources \
    --cluster_type staging \
    --only staging.test \
    deployment/templates

Useful when one --cluster_type matches multiple sibling entries (e.g. staging and staging.test both match --cluster_type staging after the suffix-strip rule) and you want to render only one of them. Repeated --only values are deduped.

If an --only value matches no entry across any template directory, the gem raises with the list of valid keys so the caller can self-correct.

Pass --spp NAME (repeatable) to expand any entry whose definitions.yaml name contains SPP-PLACEHOLDER into a per-SPP sibling output. Substitutes SPP-PLACEHOLDER with NAME and the PLACEHOLDER suffix with the suffix of NAME (everything after the last -), in both file paths and contents. Source mtimes are preserved.

gem exec -g kubernetes_template_rendering render_templates \
    --rendered-directory path/to/resources \
    --spp staging-qa02a \
    --spp staging-qa08a \
    deployment/templates

This is purely additive — the placeholder-bearing output tree is still produced, and per-SPP trees are written alongside it. Repeated --spp values are deduped.

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 the created tag, and push the .gem file to rubygems.org.

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