[maemo-developers] Autobuilder: building svn tags from garage

[From: Marius Vollmer]

ext Ed Bartosh <bartosh at gmail.com> writes:

> As I already said building in a proper order is already solved task.
> There is no need to upload packages in build order if it can be done
> automatically. It will only create extra job for developers.

Here is something to consider:

Source packages produce binary packages and they have dependies on
binary packages.  If you have a set of source packages, you need to
order them so that any source package that has a dependency on a binary
package is build after the source package that produces that binary.
This is the obvious part.

The interesting bit is this: Binary packages have dependencies on other
binary packages.  If you depend on a binary package that depends on
another binary package, you also indirectly depend on that other
package.  This means that when ordering source packages, we need to look
at all direct _and_indirect_ dependencies it has on binary packages, not
just the direct dependencies.

I think our internal buildbot (who does order source packages by their
dependencies) only looks at the direct dependencies.

Now, there is a slight complication: dependencies between binary
packages are computed at build-time.  That is, they are not known before
actually building the binary package.  The problem is still solveable if
we interleave building with sorting: I.e., we start with an incomplete
graph of dependencies (that contains all source packages and the binary
packages they produce as nodes, the dependencies from source to binary
as arrows, but not the dependencies between binary packages) and start
building those source packages that do not have any dependencies on
other packages in the graph.  Then we look at the packages that have
just been built and update the graph with the new dependencies.

Then there are cycles of dependencies, of course, or more correctly,
stronly connected components in the dependency graph.  Absent any hints
in the source packages themselves, these strongly connected components
need to be broken up by humans, I think.

I think the most advanced buildbot out there is the OpenSUSE one, which
is also by Mer,right?  Can't find a link right now.