Incidents/2022-06-10 overload varnish haproxy

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document status: final


Incident metadata (see Incident Scorecard)
Incident ID 2022-06-10 overload varnish haproxy Start 2022-06-10 14:57
Task End 2022-06-10 15:00
People paged 20 Responder count 4
Coordinators Filippo Affected metrics/SLOs
Impact For 3 minutes wiki traffic was disrupted in multiple regions at the CDN layer, affecting both cached and logged-in responses with HTTP 5xx error responses.

Lots of HTTP 429 from Varnish (due to ongoing rate-limiting) caused overload at the HAProxy level and general service disruption.




Incident Engagement ScoreCard
Question Answer


People Were the people responding to this incident sufficiently different than the previous five incidents?
Were the people who responded prepared enough to respond effectively
Were fewer than five people paged?
Were pages routed to the correct sub-team(s)?
Were pages routed to online (business hours) engineers? Answer “no” if engineers were paged after business hours.
Process Was the incident status section actively updated during the incident?
Was the public status page updated?
Is there a phabricator task for the incident?
Are the documented action items assigned?
Is this incident sufficiently different from earlier incidents so as not to be a repeat occurrence?
Tooling To the best of your knowledge was the open task queue free of any tasks that would have prevented this incident? Answer “no” if there are

open tasks that would prevent this incident or make mitigation easier if implemented.

Were the people responding able to communicate effectively during the incident with the existing tooling?
Did existing monitoring notify the initial responders?
Were all engineering tools required available and in service?
Was there a runbook for all known issues present?
Total score (count of all “yes” answers above)