Builtin public data

Elements can provide public data which can be read by other elements later in the pipeline, the format for exposing public data on a given element is described here.

Any element may use public data for whatever purpose it wants, but BuildStream has some built-in expectations of public data, which resides completely in the bst domain.

In this section we will describe the public data in the bst domain.

Integration commands

# Specify some integration commands
public:
  bst:
    integration-commands:
    - /usr/bin/update-fancy-feature-cache

The built-in integration-commands list indicates that depending elements should run this set of commands before expecting the staged runtime environment to be functional.

Typical cases for this include running ldconfig at the base of a pipeline, or running commands to update various system caches.

Integration commands of a given element are automatically run by the Element.integrate() method and are used by various plugins.

Notably the BuildElement derived classes will always integrate the build dependencies after staging and before running any build commands.

Split rules

# Specify some split rules
public:
  bst:
    split-rules:
      runtime:
      - |
        %{bindir}/*
      - |
        %{sbindir}/*
      - |
        %{libexecdir}/*
      - |
        %{libdir}/lib*.so*

Split rules indicate how the output of an element can be categorized into domains.

The split-rules domains are used by the Element.stage_artifact() method when deciding what domains of an artifact should be staged.

The strings listed in each domain are first substituted with the variables in context of the given element, and then applied as a glob style match, as understood by utils.glob()

This is used for creating compositions with the compose element and can be used by other deployment related elements for the purpose of splitting element artifacts into separate packages.

Overlap whitelist

The overlap whitelist indicates which files this element is allowed to overlap over other elements when staged together with other elements.

Each item in the overlap whitelist has substitutions applied from variables, and is then applied as a glob-style match (i.e. utils.glob()).

public:
  bst:
    overlap-whitelist:
    - |
      %{sysconfdir}/*
    - |
      /etc/fontcache