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Incidents/2023-09-20 mw-page-content-change-enrich

From Wikitech

document status: draft

Summary

Incident metadata (see Incident Scorecard)
Incident ID 2023-09-20 mw-page-content-change-enrich Start 2023-09-19 15:00:00
Task https://phabricator.wikimedia.org/T346877 End 2024-09-20 12:00:00
People paged Responder count 1
Coordinators 1 Affected metrics/SLOs https://wikitech.wikimedia.org/wiki/MediaWiki_Event_Enrichment/SLO/Mediawiki_Page_Content_Change_Enrichment
Impact There was no impact on the application SLO. This incident manifested on the passive DC deployment. The active DC deployment had no SLI degradation. Clients were not affected.

The mw-page-content-change-enrich (flink) app is failing to start in eqiad (passive DC because of a network timeout on a dependent service (thanos-swift) https://logstash.wikimedia.org/goto/ce1765e186329ed74f179d375f8df182.

The app needs swift for HA. The connection failure caused the k8s operator to fail startup. The incident was caused by incorrect egress rules. Since the app is DC agnostic, egress rules must be set for both DCs ip ranges for all deployments.

This issue was fixed by applying the proper egress rules, a re-deploying the application. The active DC deployment was not affected.

Timeline

All times in UTC.

  • 2023-09-19 15:00:00 alerts fire
  • 2023-09-20 09:10:05 gehel escalates to gmodena (#wikimedia-analytics). Troubleshooting starts.
  • 2023-09-20 09:42:23 issue is identified
  • 2023-09-20 09:46:14 triage with claime (#wikimedia-data-persistence), patch is prepared for review
  • 2023-09-20 12:00:00 patch has been deployed

There was no user visible outage.

Detection

Alerts where fired based on prometheus metrics.

The issue was escalated to the DRI.

Conclusions

  • there was no user visible outage.
  • only passive DC was affected.
  • mw-page-content-change-enrich egress rules to thanos were misconfigured.
  • we never encountered this issue before, because swift-thanos was pooled in both eqiad and codfw.
  • during DC switchover swift-thanos was depooled from eqiad.
  • the network route issue manifested.

What went well?

  • gehel was proactive in escalating the incident to the DRI.
  • instrumentation and logs supported troubleshooting.
  • claime (#wikimedia-data-persistence) promptly helped to triage the issue.

What went poorly?

  • lead time to escalation could have been shorter.
  • Early critical alerts went unnoticed by the application DRIs.

Where did we get lucky?

OPTIONAL: (Use bullet points) for example: user's error report was exceptionally detailed, incident occurred when the most people were online to assist, etc

Links to relevant documentation

Add links to information that someone responding to this alert should have (runbook, plus supporting docs). If that documentation does not exist, add an action item to create it.

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 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 atop the Google Doc kept up-to-date during the incident?
Was a public wikimediastatus.net entry created?
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)