Many i386 tests at autopkgtest.ubuntu.com failing on unsatisfiable dependencies

[Otto Kekäläinen]

While investigating https://autopkgtest.ubuntu.com/ status for packages I maintain myself I noticed that the i386 autopkgtests seem to be consistently failing on unsatisfiable dependencies. The autopkgtests environment seems to have a mix of amd64 and i386 packages, which leads to apt not being able to install all i386 dependencies.

The identical packages pass on ci.debian.net and elsewhere, so the issue is somehow related to the auto-package-testing setup at autopkgtest.ubuntu.com, but I don't know exactly. Hopefully maintainers here have some ideas what is going on.

Examples:

- https://ci.debian.net/packages/a/ahven/: all pass
- https://autopkgtest.ubuntu.com/packages/ahven: all but i386 pass
- https://autopkgtest.ubuntu.com/results/autopkgtest-mantic/mantic/i386/a/ahven/20230511_222759_6dc20@/log.gz: i386 log shows that a bunch of amd64 packages are installed, and then testbed preparation stops on
  Depends: libahven11-dev:i386 but it is not installable
  Depends: libahven30:i386 but it is not installable
  Depends: gprbuild:i386 but it is not installable

- https://ci.debian.net/packages/m/mariadb/: all pass
- https://autopkgtest.ubuntu.com/packages/mariadb: all but i386 pass
- https://autopkgtest.ubuntu.com/results/autopkgtest-mantic/mantic/i386/m/mariadb/20230528_204922_fb74b@/log.gz: i386 log shows a bunch of amd64 packages being installed/upgraded, and then fails on
  Depends: mariadb-server:i386 but it is not installable
  Depends: diffutils:i386 but it is not going to be installed

[Otto Kekäläinen (otto)]

The i386 tests are still passing on all packages I checked on autopkgtests.ubuntu.com

[Paride Legovini (paride)]

Hi Otto,

In Ubuntu (>= Focal) i386 is a partial architecture: only some packages get compiled for i386 (see [1]), and they need to be installed on a amd64 system with i386 as a foreign architecture.

The packages you mentioned (ahven, mariadb) do not get compiled for i386. You may wonder why autopkgtest runs are still sometimes attempted for those. The system is far from perfect and apparently i386 tests can still be enqueued, but they eventually fail because of missing packages.

I hope this explains.

[1] https://git.launchpad.net/~ubuntu-core-dev/ubuntu-seeds/+git/i386/tree/i386

[Steve Langasek (vorlon)]

On Thu, May 02, 2024 at 12:36:10PM -0000, Paride Legovini wrote:
> The system is far from perfect and apparently i386 tests can still be
> enqueued

If the source package builds Architecture: all binary packages, these are
published in the i386 package index; and britney doesn't know to distinguish
between these packages and Architecture: i386 binaries when deciding whether
to run autopkgtests. It is a bug that we queue tests for Architecture: all
packages on i386, *because*, as a partial arch, these package's dependencies
will always be satisfied using the native arch instead (amd64).

(It is correct to run tests for Architecture: all packages on all the other
archs.)