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Exception: Flow\Diff\FlowBoardContentDiffView: could not maintain backwards compatibility. Please use a SlotDiffRenderer.
Closed, ResolvedPublicPRODUCTION ERROR
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Description

Error
normalized_message
[{reqId}] {exception_url}   Exception: Flow\Diff\FlowBoardContentDiffView: could not maintain backwards compatibility. Please use a SlotDiffRenderer.
exception.trace
from /srv/mediawiki/php-1.37.0-wmf.1/includes/diff/DifferenceEngine.php(1442)
#0 /srv/mediawiki/php-1.37.0-wmf.1/includes/diff/DifferenceEngineSlotDiffRenderer.php(57): DifferenceEngine->generateContentDiffBody(Flow\Content\BoardContent, Flow\Content\BoardContent)
#1 /srv/mediawiki/php-1.37.0-wmf.1/includes/diff/DifferenceEngine.php(1255): DifferenceEngineSlotDiffRenderer->getDiff(Flow\Content\BoardContent, Flow\Content\BoardContent)
#2 /srv/mediawiki/php-1.37.0-wmf.1/includes/api/ApiComparePages.php(178): DifferenceEngine->getDiffBody()
#3 /srv/mediawiki/php-1.37.0-wmf.1/includes/api/ApiMain.php(1652): ApiComparePages->execute()
#4 /srv/mediawiki/php-1.37.0-wmf.1/includes/api/ApiMain.php(622): ApiMain->executeAction()
#5 /srv/mediawiki/php-1.37.0-wmf.1/includes/api/ApiMain.php(593): ApiMain->executeActionWithErrorHandling()
#6 /srv/mediawiki/php-1.37.0-wmf.1/api.php(90): ApiMain->execute()
#7 /srv/mediawiki/php-1.37.0-wmf.1/api.php(45): wfApiMain()
#8 /srv/mediawiki/w/api.php(3): require(string)
#9 {main}
Impact

Fallout from the ContentHandler MCR migration several years ago. Only happened once today so probably triggered by some uncommon operation. Causes some kind of diff to fail.

Notes

Details

Request URL
https://fr.wikipedia.org/w/api.php?action=compare&torelative=*&fromrev=*&format=*&origin=*
SubjectRepoBranchLines +/-
Avoid exceptions in action=compare APImediawiki/extensions/Flowmaster+8 -0
Customize query in gerrit

Related Objects

Event Timeline

Tgr created this task.Apr 29 2021, 7:59 PM
Restricted Application added a project: Growth-Team. · View Herald TranscriptApr 29 2021, 7:59 PM
Restricted Application added a subscriber: Aklapper. · View Herald Transcript
kostajh triaged this task as Medium priority.May 4 2021, 1:45 PM
kostajh moved this task from Inbox to Triaged on the Growth-Team board.
Krinkle moved this task from Untriaged to May 2021 on the Wikimedia-production-error board.May 6 2021, 11:11 PM
Krinkle mentioned this in Blog Post: Production Excellence #32: May 2021.Jun 21 2021, 1:31 AM
thcipriani subscribed.Jan 20 2022, 4:49 PM

Noticed a few of these today all from a single wiki. It's reproducible a GET to the URL in logstash.

Error
normalized_message
[{reqId}] {exception_url}   Exception: Flow\Diff\FlowBoardContentDiffView: could not maintain backwards compatibility. Please use a SlotDiffRenderer.
exception.trace
from /srv/mediawiki/php-1.38.0-wmf.17/includes/diff/DifferenceEngine.php(1409)
#0 /srv/mediawiki/php-1.38.0-wmf.17/includes/diff/DifferenceEngineSlotDiffRenderer.php(57): DifferenceEngine->generateContentDiffBody(Flow\Content\BoardContent, Flow\Content\BoardContent)
#1 /srv/mediawiki/php-1.38.0-wmf.17/includes/diff/DifferenceEngine.php(1221): DifferenceEngineSlotDiffRenderer->getDiff(Flow\Content\BoardContent, Flow\Content\BoardContent)
#2 /srv/mediawiki/php-1.38.0-wmf.17/includes/api/ApiComparePages.php(205): DifferenceEngine->getDiffBody()
#3 /srv/mediawiki/php-1.38.0-wmf.17/includes/api/ApiMain.php(1889): ApiComparePages->execute()
#4 /srv/mediawiki/php-1.38.0-wmf.17/includes/api/ApiMain.php(868): ApiMain->executeAction()
#5 /srv/mediawiki/php-1.38.0-wmf.17/includes/api/ApiMain.php(839): ApiMain->executeActionWithErrorHandling()
#6 /srv/mediawiki/php-1.38.0-wmf.17/api.php(90): ApiMain->execute()
#7 /srv/mediawiki/php-1.38.0-wmf.17/api.php(45): wfApiMain()
#8 /srv/mediawiki/w/api.php(3): require(string)
#9 {main}
Tgr added a comment.Jan 25 2022, 3:31 AM

The same GET request also generates a warning: Revision <revid> is the earliest revision of <title>, there is no revision for \"torelative=prev\" to compare to. (And indeed it's a Flow topic with a single revision.) So I'm a bit confused at what's being diffed to what here.

In any case, as the comment above the exception says,

// This will happen when a content model has no custom slot diff renderer, it does have
// a custom difference engine, but that does not override this method.

("this method" being DifferenceEngine::generateContentDiffBody())
Seems easy enough to fix.

gerritbot added a comment.Jan 25 2022, 4:34 AM

Change 756752 had a related patch set uploaded (by Gergő Tisza; author: Gergő Tisza):

[mediawiki/extensions/Flow@master] Avoid exceptions in action=compare API

https://gerrit.wikimedia.org/r/756752

gerritbot added a project: Patch-For-Review.Jan 25 2022, 4:34 AM
Tgr claimed this task.Jan 25 2022, 4:34 AM
Tgr edited projects, added Growth-Team (Sprint 0 (Growth Team)); removed Growth-Team.
Tgr moved this task from Incoming to Code Review on the Growth-Team (Sprint 0 (Growth Team)) board.
Urbanecm_WMF changed the task status from Open to In Progress.Jan 31 2022, 11:34 AM
kostajh moved this task from Code Review to QA on the Growth-Team (Sprint 0 (Growth Team)) board.Jan 31 2022, 12:24 PM
gerritbot added a comment.Jan 31 2022, 12:37 PM

Change 756752 merged by jenkins-bot:

[mediawiki/extensions/Flow@master] Avoid exceptions in action=compare API

https://gerrit.wikimedia.org/r/756752

ReleaseTaggerBot added a project: MW-1.38-notes (1.38.0-wmf.20; 2022-01-31).Jan 31 2022, 1:00 PM
Maintenance_bot removed a project: Patch-For-Review.Jan 31 2022, 1:11 PM
kostajh changed the task status from In Progress to Open.Feb 1 2022, 10:15 AM
Etonkovidova closed this task as Resolved.Feb 4 2022, 1:10 AM
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