Multi-Component Repository Publishing

aptly is based on a concept of package lists. Snapshots, mirrors and local repositories are lists of packages (more precisely, lists of references to packages). When merging, pulling, copying or moving packages might move from one list to another. Component is a way to break down packages into groups, usually these groups make sense only in published repository. At the same time mapping from package to component is not universal, there’s Debian way to group packages into main, contrib and non-free components, Ubuntu uses different component schema, some 3rd party repositories use components in place of distribution name (like squeeze, wheezy etc.), other use them to separate stable and testing versions of software.

In order to keep aptly simple, I’ve decided that there should be no mapping from package to component and package lists internally aren’t split by component. Each list (snapshot, mirror and local repository) is mono-component (actually there’s no component at all). When publishing repository, several lists could be published as separate components in one published repository.

By default, aptly mirrors all components from remote repository and merges them into one “single component”. If we’d like to preserve package split by components, individual mirrors should be created for each component:

$ aptly mirror create wheezy-main wheezy main
$ aptly mirror create wheezy-contrib wheezy contrib
$ aptly mirror create wheezy-non-free wheezy non-free

# update all mirrors
$ aptly mirror list -raw | xargs -n 1 aptly mirror update

We can create snapshots from each of the mirrors:

$ aptly snapshot create wheezy-main-7.5 from mirror wheezy-main
$ aptly snapshot create wheezy-contrib-7.5 from mirror wheezy-contrib
$ aptly snapshot create wheezy-non-free-7.5 from mirror wheezy-non-free

And publish all snapshots as single repository preserving component structure (publishing distribution wheezy under prefix upstream):

$ aptly publish snapshot -component=main,contrib,non-free -distribution=wheezy wheezy-main-7.5 wheezy-contrib-7.5 wheezy-non-free-7.5 upstream

aptly is smart enough to figure out component names and distribution from the mirrors, so I can omit them (commas left to identify number of components):

$ aptly publish snapshot -component=,, wheezy-main-7.5 wheezy-contrib-7.5 wheezy-non-free-7.5 upstream

Of course we could do all regular aptly operations: merging snapshots, pulling packages, etc.

The same applies to local repositories: if packages should be published as different components, several local repositories (one per component) should be created:

$ aptly repo create -distribution=wheezy -component=main my-soft-main
$ aptly repo create -distribution=wheezy -component=contrib my-soft-contrib

Local repositories could be published either directly:

$ aptly publish repo -component=, my-soft-main my-soft-contrib

Or via snapshot:

$ aptly snapshot create my-soft-main-1.0 from repo my-soft-main
$ aptly snapshot create my-soft-contrib-1.0 from repo my-soft-contrib

$ aptly publish snapshot -component=, my-soft-main-1.0 my-soft-contrib-1.0

When updating published repository, all component parts are updated at the same time. When switching published snapshots, only specified components are updated.