Entry in Developers/Maintainers with:
On paper, the Readers Web team maintain the extension. In practice, Legoktm, MaxSem, and Jdlrobson. There are no maintainers in training.
Number, severity, and age of known and confirmed security issues
0, AFAICT.
Was it a cause of production outages or incidents? List them.
It's not clear, but there may have been a production outage when DMOZ support was disabled (https://gerrit.wikimedia.org/r/#/q/If1df8ac607186eaca0d63399fe933e5306e8f1e4) in March 2017.
Does it have sufficient hardware resources for now and the near future (to take into account expected usage growth)?
Yes.
Is it a frequent cause of monitoring alerts that need action, and are they addressed timely and appropriately?
No.
When it was first deployed to Wikimedia production
Circa October 2012.
Usage statistics based on audience(s) served
RelatedSites is currently configured to search for interwiki links with the following prefixes: 'commons', 'dmoz', 'citizendium', and 'wikipedia'.
There are approximately 24000 mainspace pages on Wikivoyage that contain at least one link with one of those prefixes:: https://en.wikivoyage.org/w/index.php?search=insource%3A%2F%5C%5B%5C%5B%28commons%7Cdmoz%7Ccitizendium%7Cwikipedia%29%2Fi&title=Special:Search&profile=default&fulltext=1
Deployed to all wikis hosted by WMF but only enabled on Wikivoyage. It's deployed to one other wiki (standalone) according to WikiApiary.
Changes committed in last 1, 3, 6, and 12 months
Number of developers who committed code in the last 1, 3, 6, and 12 months
The following excludes i18n/CI updates.
1 month:
N/A
3 months:
Umherirrender: rERSI92907c4429c1: Improve some parameter docs
6 months:
12 months:
MaxSem: rERSI1b8efbd8723d: DMOZ is closing today, don't display links to it
MaxSem: rERSI2134e21b4b62: Unbreak after my If1df8ac607186eaca0d63399fe933e5306e8f1e4
Reliance on outdated platforms (e.g. operating systems)
None.
Number and age of open patches
None.
Number and age of open bugs
2
Number of known dependencies?
None.
Is there a replacement/alternative for the feature? Is there a plan for a replacement?
The "Other projects sidebar" beta feature could easily replace the RelatedSites extension (see T2708: Interproject links and T103102: [Story] Take in other projects sidebar out of beta features).
Relatedly, there's a task around de-deploying the RelatedSites extension, which appears to have stalled after some work, including tracking on-wiki discussions about de-deploying the extension: T128326: Undeploy the RelatedSites extension (used on Wikivoyage).