Fix: sometimes, changes to subsections are not reflected in the Studio Search Index

[bradenmacdonald]

Description

There is a race condition that causes some changes to not be reflected in the Studio search index.

Technical Details

What's happening is that the XBlock is updated with modulestore.update_item() in the initial request, that function immediately triggers the XBLOCK_UPDATED signal. However, when our handler processes that in a worker, even though there is no active MySQL transaction, the modulestore "bulk operation" may still be active, so the actual modulestore data in mongo/mysql hasn't been updated yet. The data only gets committed when the outermost bulk operation scope is exited.

I couldn't find any existing mechanism to listen for that "actual commit" of draft content, because the code seems to assume that other parts of the system only need to know when new content has been published, not when new draft content has been committed to the DB. So I had to add that as a new capability.

Testing instructions

In cms/envs/devstack.py set CELERY_ALWAYS_EAGER = False.

1. Rename any subsection in a course
2. Open the course search (from the header of the course authoring MFE, while viewing the same course outline)
3. Search for the name of the subsection
4. In some cases (especially if it's not the first time you've made a change since the CMS and CMS worker were restarted), you will see that the name of the subsection in the search index is out of date.

We have focused testing on renaming subsections, but this likely affects other types of edits.

Deadline

TBD

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[bradenmacdonald]

@ormsbee Would you be able to review this PR? We'd also like to backport it to Redwood, as it's a bugfix.

[ChrisChV]

@yusuf-musleh Looks good 👍

• I tested this: I followed the testing instructions with: Sections, Units and components
• I read through the code and considered the security, stability and performance implications of the changes.
• I tested that the UI can be used with a keyboard only (tab order, keyboard controls).
• Includes tests for bugfixes and/or features added.
• Includes documentation

[ormsbee]

Nice! This is honestly a lot cleaner than I thought it would be when you described the problem. 😛

[bradenmacdonald]

Haha yeah @ormsbee I'm happy with how the fix shaped up; we were able to implement it without needing to change too much.

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[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.