Changes/BuildWithDNF5

[DRAFT] Build Fedora with DNF 5

This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

Summary

We are proposing to change the Mock configuration in Mock (mock-core-configs), Koji, and Copr to use DNF 5 as Mock's package manager instead of DNF 4. DNF 5 would be used by Mock to install build dependencies into chroots for package builds. This change is related to the build infrastructure and is distinct from changing the default package manager in Fedora.

Owner

• Name: Evan Goode
• Email: egoode@redhat.com

• Name: Pavel Raiskup
• Email: praiskup@redhat.com

Current status

• Targeted release: Fedora Linux 40
• Last updated: 2023-10-19
• [<will be assigned by the Wrangler> devel thread]
• FESCo issue: <will be assigned by the Wrangler>
• Tracker bug: <will be assigned by the Wrangler>
• Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

DNF 5 is a new package manager intended to replace DNF: https://dnf5.readthedocs.io/en/latest/about.html. It offers significant performance improvements over DNF while achieving lower memory usage and disk footprint. The switch to DNF 5 was originally planned for Fedora 39, but it's been postponed to (likely) Fedora 41: https://pagure.io/fesco/issue/3039.

In the meantime, we would like to start building Fedora with DNF 5. The set of package management features that Mock needs for setting up buildroots is small compared to the full capabilities of DNF, so it's a good place to start deploying DNF 5. We will be able to test the stability of DNF 5 at a large scale and gather data about its performance.

The Mock developers have been working alongside the DNF 5 developers for a while to ensure Mock can use DNF 5, per this tracking issue: https://github.com/rpm-software-management/mock/issues/894. The two remaining items on that issue are "optional" items that are not blocking this proposed change.

Benefit to Fedora

With the switch to DNF 5 as the default package manager on the horizon, the build infrastructure offers an opportunity to subject a crucial subset of DNF 5's features to heavy testing. This change will let us verify that every build dependency in the distribution is installable by DNF 5.

In addition, we expect a substantial performance improvement for package builds that spend a significant portion of their time installing build dependencies. Larger, compilation-heavy packages likely won't see much improvement; the difference will be most apparent when building many smaller packages. Switching the build system over to DNF 5 will let us measure the performance improvement over DNF across a wide variety of install transactions.

Scope

• Proposal owners:

The work to support DNF 5 in Mock is done already. This change should be as simple as setting the Mock option config_opts['package_manager'] = 'dnf5' in Mock, Koji, and Copr for F40+ builds (Koji config option exists from the yum -> dnf4 era). The dnf5 doesn't necessarily have to be installed on building hosts - in such a case, Mock will automatically use /bin/dnf-3 (DNF4) from the host to install DNF5 into the bootstrap chroot, to further use *that* DNF5 for build chroot installation.

• Other developers:

• Release engineering: #Releng issue number

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Community Initiatives:

User Experience

This change will mostly be invisible to users. The builds, namely the buildroot preparation, will be much faster.

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?)

Revert the F40 Mock configuration in Koji and Copr back to using dnf.

• Contingency deadline:

F40 Beta freeze

• Blocks release? Yes