Incidents/2021-09-18 appserver latency

document status: final

Summary

Slow database queries resulted in php-fpm worker exhaustion.

Impact: For about 10 minutes, backends were slow or unavailable for all wikis. This affected logged-in users, most bots/API queries, and some page views from unregistered users (pages that were recently edited or otherwise expired from the CDN cache).

Documentation:

• Public incident task: T291311
• Similar to Incident documentation/2021-09-04 appserver latency and Incident documentation/2021-04-15 appserver latency.

Actionables

• T284419 (restricted)