Bug 1757460

Summary:	dnf does not consider newer module versions when a new context is added
Product:	Red Hat Enterprise Linux 8	Reporter:	Petr Pisar <ppisar>
Component:	dnf	Assignee:	Jaroslav Mracek <jmracek>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Eva Mrakova <emrakova>
Severity:	unspecified	Docs Contact:
Priority:	high
Version:	8.2	CC:	astepano, james.antill, jblazek, jorton, jplesnik, lberton, mdomonko, psabata, sct
Target Milestone:	rc	Keywords:	Triaged
Target Release:	8.3
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:
Clones:	1763593 1837369 (view as bug list)		Environment:
Last Closed:	2020-07-08 12:45:43 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1763593
Bug Blocks:	1666770, 1713592, 1825061, 1837369

Description Petr Pisar 2019-10-01 15:01:38 UTC

We have two streams of perl in RHEL-8.1.0:

perl:5.24
perl:5.26

We have a stream of perl-DBI built for both perl streams, that means two contexts:

perl-DBI:1.641:8010020190322130042:16b3ab4d for perl:5.26
perl-DBI:1.641:8010020190322130042:e1f37755 for perl:5.24

Now I added a new perl:5.30 stream (bug #1713592) into RHEL-8.2.0:

perl:5.30

I can enable perl:5.30 stream:

# dnf --quiet --allowerasing module enable perl:5.30 
Problems in request:
Modular dependency problems with Defaults:

 Problem: conflicting requests
  - module perl-DBI:1.641:8010020190322130042:16b3ab4d-0.x86_64 requires module(perl:5.26), but none of the providers can be installed
  - module perl-DBI:1.641:8010020190322130042:e1f37755-0.x86_64 requires module(perl:5.24), but none of the providers can be installed
  - module perl:5.26:820181219174508:9edba152-0.x86_64 conflicts with module(perl:5.30) provided by perl:5.30:8020020190927112308:1b153fc7-0.x86_64
  - module perl:5.30:8020020190927112308:1b153fc7-0.x86_64 conflicts with module(perl:5.26) provided by perl:5.26:820181219174508:9edba152-0.x86_64
  - module perl:5.24:8010020190529084201:3af8e029-0.x86_64 conflicts with module(perl:5.30) provided by perl:5.30:8020020190927112308:1b153fc7-0.x86_64
  - module perl:5.30:8020020190927112308:1b153fc7-0.x86_64 conflicts with module(perl:5.24) provided by perl:5.24:8010020190529084201:3af8e029-0.x86_64
Is this ok [y/N]: Y

# dnf --quiet --allowerasing module list perl | grep 5.30
perl 5.30 [e] common [d], minimal Practical Extraction and Report Language

Then I rebuilt perl-DBI:1.641 in a new version to provide perl-DBI builds for all three contexts:

perl-DBI-1.641-8020020190923125347.80dfbdb3 for perl:5.30
perl-DBI-1.641-8020020190923125347.31e953cd for perl:5.26
perl-DBI-1.641-8020020190923125347.a7d630c8 for perl:5.24

Now I want to enable perl-DBI:1.641 stream. I expect perl-DBI-1.641-8020020190923125347.80dfbdb3 will satisfy the modular dependencies:

# dnf --quiet --allowerasing module enable perl-DBI:1.641
Error: Problems in request:
Modular dependency problems:

 Problem: conflicting requests
  - module perl-DBI:1.641:8010020190322130042:16b3ab4d-0.x86_64 requires module(perl:5.26), but none of the providers can be installed
  - module perl-DBI:1.641:8010020190322130042:e1f37755-0.x86_64 requires module(perl:5.24), but none of the providers can be installed
  - module perl:5.26:820181219174508:9edba152-0.x86_64 conflicts with module(perl:5.30) provided by perl:5.30:8020020190927112308:1b153fc7-0.x86_64
  - module perl:5.30:8020020190927112308:1b153fc7-0.x86_64 conflicts with module(perl:5.26) provided by perl:5.26:820181219174508:9edba152-0.x86_64
  - module perl:5.24:8010020190529084201:3af8e029-0.x86_64 conflicts with module(perl:5.30) provided by perl:5.30:8020020190927112308:1b153fc7-0.x86_64
  - module perl:5.30:8020020190927112308:1b153fc7-0.x86_64 conflicts with module(perl:5.24) provided by perl:5.24:8010020190529084201:3af8e029-0.x86_64

But DNF rejects it. Reading the error message suggests that DNF ignores 8020020190923125347 perl-DBI version completely and for some reason it insists on using the old 8010020190322130042 version.

I consider this a bug it prevents me from adding perl:5.30 into RHEL-8.2.0.


Tested with:

dnf-4.2.7-6.el8.noarch
libmodulemd-2.5.0-2.el8.x86_64

If you observe more error messages, just disable the offending modules.

Comment 2 Jaroslav Mracek 2019-10-03 07:00:48 UTC

For the further development of modularity including resolving this issue, DNF team needs specifications (distribution restrictions) what is allowed during the life cycle of stream/module. Like changes in rpm artifacts (adding, removal, replacing), profiles, or module dependencies. The current situation with no restrictions limits changes in modular solving. The restrictions must be announced as a restriction and not as a example of a usage. Additional step would be that the release process must reject any update that do not fulfill the requirements.

From the DNF side the most critical part in modular dependency solving is related to missing upgrade path between contexts. The upgrade path is synthetically calculated but we cannot ensure that the new version of the module is child of any previous version. The situation result in:
1. Errors that are not errors (Current behavior)
2. Ignoring critical problems

The specific part in modular dependencies is represented by platform_id. Platform ID cannot be distinguished from real dependencies but it is strictly artificial object nearly identical to releasever. From our experience we discovered that auto-detection from metadata brakes some user-case where standard distribution based on releasever works.

My question is what the plan?

Comment 6 Jaroslav Mracek 2020-02-26 12:48:58 UTC

I create a github repository with modify repodata that will resolve adding new context or EOL. See: https://github.com/j-mracek/module_repos. The solution is based on filling metadata gaps by duplication of existing data with modified version. It does not requires any additional rpm or module builds.