(Tagging this with Analytics considering general EL code stewardship and the current schema maintainer, although I honestly don't know who is in the best position to fix this.)

I used data from this schema in T216185. My experience was similar to what @Tbayer mentions in that some preferences appear to have issues with duplication, and some do not. In this case the echo-notifications-blacklist and email-blacklist preferences were affected. It also seems that the issue changed over time, in other words that some users logged lots of preference changes during certain periods, and not during others.

This schema has no owner and it's the owner who has to correct the instrumentation.
cc @jlinehan fyi

In T249386, I used prefupdate data to determine the opt-in and opt-out rate of the discussiontools-betaenable property. While reviewing the data, I found there were 100 duplicate events recorded for this property between March 31 and June 26th.

Product Infrastructure data as the new crowned owners of this schema will be reviewing and hoping to merge here soon.

SELECT
  year, month,
  CONCAT_WS(', ', COLLECT_SET(event.property)) AS properties_affected,
  COUNT(1) AS duplicated_events
FROM (
  SELECT year, month, event, COUNT(1) AS copies
  FROM event.prefupdate 
  WHERE year = 2020
  GROUP BY year, month, event
  HAVING copies > 1
) AS events
GROUP BY year, month
ORDER BY year, month
LIMIT 1000000;

So…still an issue

I've been poking at this as time permits but haven't yet managed to track down a cause. Interestingly, eyeballing some data from yesterday, it seems to happen particularly often for popupsreferencepreviews events.

I'm curious to see whether this problem persists after the migration of this instrument to MEP is finished. (At time of writing, it's only using MEP on testwiki.) If nothing else, it'll give us some better metadata to use for investigation.

OK, after running a couple of queries for the past couple of days, it looks like the worst offender is in fact mf_amc_optin, followed by popupsreferencepreviews, then discussiontools-betaenable, then a handful of others with a duplicate or two per day.

For example:

SELECT event.property AS property, COUNT(*) AS duplicated_events
FROM (
  SELECT event, COUNT(*) AS copies
  FROM event.prefupdate 
  WHERE year = 2021 AND month = 2 AND day = 15
  GROUP BY event
  HAVING COUNT(*) > 1) AS events
GROUP BY event.property
ORDER BY duplicated_events DESC;

returns:

The only factor I can find in common among the duplicated events is that the vast majority of them are coming from mobile user agents. (No particular platform or browser stands out, however.)

Change 665236 had a related patch set uploaded (by Mholloway; owner: Michael Holloway):
[mediawiki/extensions/MobileFrontend@master] Fix: Save user options only once when Advanced Mode is toggled

https://gerrit.wikimedia.org/r/665236

I believe a review here is required from our team.

Change 665236 merged by jenkins-bot:
[mediawiki/extensions/MobileFrontend@master] Fix: Save user options only once when Advanced Mode is toggled

https://gerrit.wikimedia.org/r/665236

Test Result - Beta

Status: ✅ PASS
Environment: beta
OS: macOS Big Sur
Browser: Chrome
Device: MBP
Emulated Device: iPhone 11 Pro Max

Test Artifact(s):

QA Steps

AC1: Verify that opt-in and out from Beta and AMC modes work properly on a mobile site.

AMC On	AMC Off

AC2: Also, please double-check that saving user preferences works with, and without Javascript.

JS Enabled	JS Disabled

Change 670923 had a related patch set uploaded (by Mholloway; owner: Michael Holloway):
[mediawiki/extensions/WikimediaEvents@master] onUserSaveOptions: Warn and abort when originalOptions are empty

https://gerrit.wikimedia.org/r/670923

From my preliminary spot checking, the patch appears to have eliminated duplicates on the group 0 and 1 wikis to which it's been deployed so far. I look forward to seeing the results after it's promoted to group 2 this afternoon.

Also, I've just uploaded a follow-up patch to help unearth remaining cases of similar behavior (if any) and prevent regressions.

@Mholloway: Thoughts on T277229?

Change 670979 had a related patch set uploaded (by Mholloway; owner: Michael Holloway):
[mediawiki/extensions/MobileFrontend@master] Save user options only once when Advanced Mode is toggled, take 2

https://gerrit.wikimedia.org/r/670979

@nray Do you plan to review updated patch (updated only to add a null check), or can @jlinehan and I get it merged today to roll out this week?

Change 670923 merged by jenkins-bot:
[mediawiki/extensions/WikimediaEvents@master] onUserSaveOptions: Warn and abort when originalOptions are empty

https://gerrit.wikimedia.org/r/670923

@Mholloway Sorry for the delay on that, I will for sure review it today after I get done with meetings

No worries, @nray! Thanks for the update.

Change 670979 merged by jenkins-bot:
[mediawiki/extensions/MobileFrontend@master] Save user options only once when Advanced Mode is toggled, take 2

https://gerrit.wikimedia.org/r/670979

@Edtadros There was a patch on this ticket that was reverted, modified, and then merged again so please follow the same QA steps you did in https://phabricator.wikimedia.org/T218835#6912461 to make sure everything is still working

In T218835#6938556, @nray wrote:

@Edtadros There was a patch on this ticket that was reverted, modified, and then merged again so please follow the same QA steps you did in https://phabricator.wikimedia.org/T218835#6912461 to make sure everything is still working

you got it.

Test Result - Beta

Status: ✅ PASS
Environment: beta
OS: macOS Big Sur
Browser: Chrome
Device: MBP
Emulated Device: iPhone 11 Pro Max

Test Artifact(s):

QA Steps

AC1: Verify that opt-in and out from Beta and AMC modes work properly on a mobile site.

AMC On	AMC Off

AC2: Also, please double-check that saving user preferences works with, and without Javascript.

JS Enabled	JS Disabled

The fixed patch finally rolled out on Tuesday 3/30 with 1.36.0-wmf.36. It looks like it's almost completely eliminated duplicate PrefUpdate events, down from several hundred duplicates per day prior to the change. Yesterday there were no duplicate events, and today so far there is only one duplicate popupsreferencepreviews event.