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Developing Butane

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Project layout

Internally, Butane has a versioned base component which contains support for a particular Ignition spec version, plus distro-independent sugar. New base functionality is added only to the experimental base package. Eventually the experimental base package is stabilized and a new experimental package created. The base component is versioned independently of any particular distro, and its versions are not exposed to the user. Client code should not need to import anything from base.

Each config variant/version pair corresponds to a config package, which derives either from a base package or from another config package. New functionality is similarly added only to an experimental config version, which is eventually stabilized and a new experimental version created. (This will often happen when the underlying package is stabilized.) A config package can contain sugar or validation logic specific to a distro (for example, additional properties for configuring etcd).

Packages outside the Butane repository can implement additional config versions by deriving from a base or config package and registering their variant/version pair with config.

  • config/ — Top-level TranslateBytes() function that determines which config version to parse and emit. Clients should typically use this to translate configs.

  • config/common/ — Common definitions for all spec versions, including translate options structs and error definitions.

  • config/*/vX_Y/ — User facing definitions of the spec. Each is derived from another config package or from a base package. Each one defines its own translate functions to be registered in the config package. Clients can use these directly if they want to translate a specific spec version.

  • config/util/ — Utility code for implementing config packages, including the (un)marshaling helpers. Clients don't need to import this unless they're implementing an out-of-tree config version.

  • base/ — Distro-agnostic code targeting individual Ignition spec versions. Clients don't need to import this unless they're implementing an out-of-tree config version.

  • internal/ — main, non-exported code.

Creating a release

Create a release checklist and follow those steps.

The build process

Note that the binaries released in this repository are not built using the build script from this repository but using a butane.spec maintained in Fedora rpms/butane. This build process uses the go-rpm-macros to set up the Go build environment and is subject to the Golang Packaging Guidelines.

Consult the Package Maintenance Guide and the Pull Requests Guide if you want to contribute to the build process.

In case you have trouble with the aforementioned standard Pull Request Guide, consult the Pagure documentation on the Remote Git to Pagure pull request workflow.

Bumping spec versions

This checklist describes bumping the Ignition spec version, base version, and distro versions. If your scenario is different, modify to taste.

Stabilize Ignition spec version

  • Bump go.mod for new Ignition release and update vendor.
  • Update imports. Drop -experimental from Ignition spec versions in */translate_test.go.

Bump base version

  • Rename base/vB_exp to base/vB and update package statements. Update imports.
  • Copy base/vB to base/vB+1_exp.
  • Update package statements in base/vB+1_exp.

Bump distro version

  • Rename config/distro/vD_exp to config/distro/vD and update package statements. Update imports.
  • Drop -experimental from init() in config/config.go.
  • Drop -experimental from examples in docs/.
  • Copy config/distro/vD to config/distro/vD+1_exp.
  • Update package statements in config/distro/vD+1_exp. Bump its base dependency to base/vB+1_exp.
  • Import config/vD+1_exp in config/config.go and add distro C+1-experimental to init().

Bump Ignition spec version

  • Bump Ignition types imports and rename ToIgnI and TestToIgnI functions in base/vB+1_exp. Bump Ignition spec versions in base/vB+1_exp/translate_test.go.
  • Bump Ignition types imports in config/distro/vD+1_exp. Update ToIgnI function names, util calls, and header comments to ToIgnI+1.

Update docs

  • Copy the C-exp spec doc to C+1-exp. Update the header and the version numbers in the description of the version field.
  • Rename the C-exp spec doc to C. Update the header, delete the experimental config warning, and update the version numbers in the description of the version field. Update the nav_order to one less than the previous stable release.
  • Update docs/specs.md.
  • Update docs/upgrading-*.md for the new spec version. Copy the relevant section from Ignition's doc/migrating-configs.md, convert the configs to Butane configs, convert field names to snake case, and update wording as needed. Add subsections for any new Butane-specific features.