We send the full textbox contents back to EventLogging for the TwoColConflictConflict schema. With a maximum payload length around 1.4kB, this the long requests to be truncated, failing validation. They never make it to our database. About 20 conflict events are dropped per day.
Stop sending full text to EventLogging, send the first 256 chars or so.
Change 582545 had a related patch set uploaded (by Awight; owner: Awight):
[mediawiki/extensions/TwoColConflict@master] Shorten EventLogging payload
Change 582545 merged by jenkins-bot:
[mediawiki/extensions/TwoColConflict@master] Shorten EventLogging payload
Something's wrong, we still have a lot of errors: https://logstash.wikimedia.org/goto/ba6b0c0d6de380074bda725e63922c0e
I think the continuing truncation is multibyte-related. Spot-checking a few events, they're all non-Latin and each character is encoded like: "%5Cu0430", or 8 bytes per character. Even truncating at 128 multibyte characters is yielding 2048 bytes of payload for just the two text strings. Next, let's try just dropping these two fields.
Change 585821 had a related patch set uploaded (by Awight; owner: Awight):
[mediawiki/extensions/TwoColConflict@master] Stop eventlogging free text fields
Change 585821 merged by jenkins-bot:
[mediawiki/extensions/TwoColConflict@master] Stop eventlogging free text fields
Mentioned in SAL (#wikimedia-operations) [2020-04-06T11:53:14Z] <awight@deploy1001> Synchronized php-1.35.0-wmf.26/extensions/TwoColConflict: SWAT: [[gerrit:586309|Backport talk page and EventLogging changes (T248243, T249404) (duration: 00m 59s)