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Module Context Upgrade Paths
Summary
Modularity doesn't define any upgrade paths among module Contexts. Fix that by introducing following changes:
- Change NSVCA module identifier to NSCVA; NSC will define a group of packages that belong together (a "repository")
- Enabling a Stream will resolve a module transaction and store information about
- Change stream expansion so related module builds always end up with the same Context
- Use only the latest Version of a module to compute module Stream dependencies
- Allow Context to be human-readable rather than the current hash (Context is close to the %{?dist} macro)
- Drop explicit runtime dependency on platform ($releasever should be good enough)
Owner
- Name: Daniel Mach
- Email: dmach@redhat.com
Current status
- Targeted release: Fedora 34
- Last updated: 2020-06-25
- 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
Modules are identified with N:S:V:C:A identifier. This ID doesn't explicitly determine how the related modules should be grouped together and ordered to enable upgrade paths among them.
This has several consequences:
- Modules are difficult to work with, the relations are not obvious at the first sight.
- DNF literally guesses the upgrade paths by resolving a transaction for each module version and it frequently fails to find a solution.
Feedback
Benefit to Fedora
- Allow stream dependency changes (remember libgit2 problem?).
- Make modularity less complex and easier to understand for end-users, sysadmins, and also packagers.
- DNF will not error out on module dependency problems that frequently.
Scope
- Proposal owners:
- Create modulemd v3 document that supports the new stream expansion.
- Work with libmodulemd upstream to implement modulemd v3.
- Work with MBS developers to implement the new stream expansion.
- Other developers:
- Change modulemd sources to explicitly list contexts to be expanded by MBS
- Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)
- Policies and guidelines: N/A (not a System Wide Change)
- Trademark approval: N/A (not needed for this Change)
Upgrade/compatibility impact
N/A (not a System Wide Change)
How To Test
- A module dependency change in a Stream must work.
- example:
- n:s:c:1:x86_64 requires nodejs:10
- n:s:c:2:x86_64 requires nodejs:12
- example:
- Context gaps no longer cause module dependency problems.
- example:
- n:s:pl528:1:x86_64 requires perl:5.28
- there's no context for perl:5.30 in version 1
- n:s:pl528:2:x86_64 requires perl:5.28
- n:s:pl530:2:x86_64 requires perl:5.30
- there's no context for perl:5.28 in version 3
- n:s:pl530:3:x86_64 requires perl:5.30
- example:
User Experience
Users will not experience modularity issues in DNF that frequently.
Dependencies
N/A (not a System Wide Change)
Contingency Plan
- Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
- Contingency deadline: N/A (not a System Wide Change)
- Blocks release? N/A (not a System Wide Change), Yes/No
- Blocks product? product
Documentation
Changes to modularity documentation will be made during implementing this Change.