Incidents/2022-07-10 thumbor

document status: draft

Summary

Incident metadata (see Incident Scorecard)
Incident ID	2022-07-10 thumbor	Start	YYYY-MM-DD hh:mm:ss
Task	T312722	End	YYYY-MM-DD hh:mm:ss
People paged		Responder count	3
Coordinators		Affected metrics/SLOs
Impact	For several days, Thumbor p75 service response times gradually regressed by several seconds.

Due to a uptream bug introduced in a firejail update, Thumbor constantly restarting itself. This lead to increased error rates, and also increased delays from the HAProxy in front of it.

Detection

Write how the issue was first detected. Was automated monitoring first to detect it? Or a human reporting an error?

Copy the relevant alerts that fired in this section.

Did the appropriate alert(s) fire? Was the alert volume manageable? Did they point to the problem with as much accuracy as possible?

TODO: If human only, an actionable should probably be to "add alerting".

Links to relevant documentation

Grafana dashboard: Thumbor

Actionables

…

Create a list of action items that will help prevent this from happening again as much as possible. Link to or create a Phabricator task for every step.

Add the #Sustainability (Incident Followup) and the #SRE-OnFIRE (Pending Review & Scorecard) Phabricator tag to these tasks.

Scorecard

Incident Engagement ScoreCard
	Question	Answer (yes/no)	Notes
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 the engineering tools that were to be used during the incident, available and in service?
	Were the steps taken to mitigate guided by an existing runbook?
Total score (count of all “yes” answers above)