Rubric as requested by [[ https://www.mediawiki.org/wiki/Code_stewardship_reviews#Rubric | documentation ]]:
**A succinct problem statement to give context for why the review was initiated.**
UserMerge is an extension that allows merging two accounts. While very useful it doesn't work on Wikimedia, or better said, we are adviced not to use it. In order to merge two user accounts, all edits and log data gets merged. Wikimedia's active development of new extensions, API and other features, merging an user account is no longer just merging edits and logs. UserMerge has not been kept up with the whole updates and usage of this extension is likely to cause incomplete or broken user account merges that will need to be manually fixed. UserMerge does also perform heavy DB queries/full table scans that have caused huge replag in the past when usage was attempted at dewiki and commonswiki (see data below). No local or global group is currently granted the `'usermerge'` permission, making the extension also unused.
**Entry in Developers/Maintainers with:**
@Legoktm is listed as maintainer.
**Code Steward**
None.
**Maintainer (non-WMF team)**
No team.
**In-training**
None.
**Number, severity, and age of known and confirmed security issues**
None.
**Was it a cause of production outages or incidents? List them.**
- {T104686} + has a summary of the issues found. T104686#3490006 indicates that UserMerge is not FlaggedRevs friendly.
- {T156584} is/was an attempt to have UserMerge overhauled and usable again. At T156584#4203549 and T156584#4557145 you can find more reasons why I'm filing this task.
**Does it have sufficient hardware resources for now and the near future (to take into account expected usage growth)?**
I can't answer that question with the information I have.
**Is it a frequent cause of monitoring alerts that need action, and are they addressed timely and appropriately?**
No, because we don't use it as it's unreliable and/or cause huge DB load.
**When it was first deployed to Wikimedia production**
2012 in rOMWC57e3970888acd367e835eacb6d40556af0e57767
**Usage statistics based on audience(s) served**
N/A
**Changes committed in last 1, 3, 6, and 12 months**
* [[ https://gerrit.wikimedia.org/r/#/q/project:mediawiki/extensions/UserMerge+status:merged+-owner:%22L10n-bot%22+-owner:%22Libraryupgrader%22+branch:master | All merged changes NOT being L10n-bot or Libraryupgrader ]]
** on 2018 we had 14 changes in total.
**Reliance on outdated platforms (e.g. operating systems)**
N/A
**Number and age of open patches**
We currently have [[ https://gerrit.wikimedia.org/r/#/q/status:open+project:mediawiki/extensions/UserMerge | 9 open patches ]]. The oldest one is https://gerrit.wikimedia.org/r/#/c/139085/ opened 3 years and 3 months ago.
**Number and age of open bugs**
We currently have [[ https://phabricator.wikimedia.org/maniphest/?project=PHID-PROJ-oz7ku6n4e2wf4ntekt2f&statuses=open()&group=none&order=newest#R | 21 open Tasks ]]. The oldest one is from year 2016.
**Number of known dependencies?**
N/A
**Is there a replacement/alternative for the feature? Is there a plan for a replacement?**
No.
**Submitter's recommendation**
If there's no plans or resources or people interested in keeping up with the required maintenance of this extension to work on the projects, my recomendation is to undeploy UserMerge from Wikimedia Production.