Metadata Env Buildkite Plugin

A Buildkite plugin for retrieving build metadata values and setting them as environment variables. This provides a nice way to pass environment variables between steps in a build, even when their values are dynamically calculated.

Notably, this plugin is just syntactic sugar for export FOO=$(buildkite-agent meta-data get env-FOO), but can be used with other plugins where the command isn't executed directly on the agent (e.g. the docker-compose plugin)

Usage

This plugin uses the prefix env- in build metadata to denote a piece of metadata that can be exported as an environment variable. Set the value you're interested in earlier in the build, using the buildkite-agent meta-data set command:

steps:
  - label: "Set and store an env var"
    command:
      - export FOO=$(something-dynamic)
      - buildkite-agent meta-data set env-FOO ${FOO}

Later, in a different build step, use the plugin to retrieve the value you set and recreate the environment variable:

steps:
  - label:   "Retrieve and use an env var"
    command: echo "The value was $FOO"
    plugins:
      - vital-software/metadata-env#0.0.1:
          get: [FOO]

Configuration

get

A list of environment variable names. Their values will be retrieved from the build metadata, if set, and used for the current command.

TODO

• This plugin initially came with logic to support a corresponding set configuration, where it would store env var variables back to the metadata, post-command. However, if the value was calculated within a build step, the post-command hook won't have access to it. Suggestions for working around that are welcome.

Developing

To run the tests:

docker-compose run --rm tests

License

MIT (see LICENSE)