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Incidents/2022-07-03 shellbox request spike

From Wikitech

document status: in-review


Incident metadata (see Incident Scorecard)
Incident ID 2022-07-03 shellbox request spike Start 2022-07-03 11:17:00
Task T310557 End 2022-07-03 11:33:00
People paged 26 (twice) Responder count 10
Coordinators lsobanski Affected metrics/SLOs
Impact For 16 minutes, edits and previews for pages with Score musical notes were too slow or unavailable.
Shellbox Grafana dashboard

An increase in Score requests (musical note rendering) from Parsoid overwhelmed the Shellbox service. This was mitigated by allocating more k8s pods to Shellbox. The overload took place from 11:17 to 11:33.

From the Grafana dashboard, we see that a majority of requests took over 5,000ms (5s) instead of less the usual 10ms (0.01s), and for two minutes 11:25-11:27 requests actually failed with HTTP 503 instead.

From the Logstash dashboard, we measure approximately 35,000 failed requests during this time. Of which 99.9% were from Parsoid, for de.wikipedia.org requests that render musical notes through the Score extension. 26K received HTTP 503, and 9K received HTTP 504. The remaining 0.1% were edits or pageviews calling Shellbox for syntax highlighting.

See 2022-07-11 Shellbox and parsoid saturation for re-occurrence and follow up action items.

Shellbox service errors in Logstash




Incident Engagement ScoreCard
Question Answer


People Were the people responding to this incident sufficiently different than the previous five incidents? no
Were the people who responded prepared enough to respond effectively yes
Were fewer than five people paged? no
Were pages routed to the correct sub-team(s)? no
Were pages routed to online (business hours) engineers? Answer “no” if engineers were paged after business hours. yes
Process Was the incident status section actively updated during the incident? yes
Was the public status page updated? no
Is there a phabricator task for the incident? yes
Are the documented action items assigned? no
Is this incident sufficiently different from earlier incidents so as not to be a repeat occurrence? no
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? yes
Did existing monitoring notify the initial responders? yes
Were the engineering tools that were to be used during the incident, available and in service? yes
Were the steps taken to mitigate guided by an existing runbook? no
Total score (count of all “yes” answers above) 7