EventLogging suffered from performance problems and data loss from Tuesday 2015-05-05 22:00 UTC to Wednesday 2015-05-06 20:00 UTC (22 hours).
During that period, an exceptional amount of events were sent to EL server for a given schema. The system could not handle them properly, and this caused data loss (30%-40% during the period) and some small gaps in the db. All schemas were affected.
The missing data will be backfilled during this week.
Phab Task: https://phabricator.wikimedia.org/T98588 Incident documentation: https://wikitech.wikimedia.org/wiki/Incident_documentation/20150506-EventLog...
Cheers,
Marcel