Date	May 10, 2022
Team(s)	Arch-BOM, Cosmonauts, Support
Summary	Due to a change in the CourseWaffleFlag signature, timed with a very recent CourseWaffleFlag addition in another repo, the new LTI related flag broke.
Impact	LTI xblocks were not editable for about 27 hours starting 2022-05-02 5:00PM ET. Two reports from partners.
Lesson Learned	Handled exceptions in xblocks are hard/impossible to find via monitoring, as is LTI generally.

Technical Cause

On May 9th, 2022, we merged [BB-5559] Adds support for external LTI configurations using openedx-filters by tecoholic · Pull Request #239 · openedx/xblock-lti-consumer OSPR which updated lti-consumer-xblock with a new CourseWaffleFlag. This is a pretty big PR and a major version bump.
Later that day, we merged fix: update lti-consumer-xblock library to v4.0.1 by schenedx · Pull Request #30359 · openedx/edx-platform which upgraded lti-consumer-xblock in edx-platform. This is an extension of the above to get the new version into platform.
On May 10, 2022, as part of Legacy Toggle deprecation work (https://2u-internal.atlassian.net/browse/OSPR-6637), we merged FC-0001: upgrade original CourseWaffleFlag by dyudyunov · Pull Request #30351 · openedx/edx-platform with backward incompatible change to signature of CourseWaffleFlag. All known uses were updated beforehand but the above PRs added a new one. Also a large PR, part of a big multi-step process to remove deprecated code and adjust the signature.
When this was deployed, LTI editing in Studio became broken.

Architecture and Engineering