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Incidents/2021-11-10 cirrussearch commonsfile outage

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document status: draft

Summary and Metadata

The metadata is aimed at helping provide a quick snapshot of context around what happened during the incident.

Incident ID 2021-11-10 cirrussearch commonsfile outage UTC Start Timestamp: YYYY-MM-DD hh:mm:ss
Incident Task https://phabricator.wikimedia.org/T299967 UTC End Timestamp YYYY-MM-DD hh:mm:ss
People Paged <amount of people> Responder Count <amount of people>
Coordinator(s) Names - Emails Relevant Metrics / SLO(s) affected Relevant metrics

% error budget

Summary: For about 2.5 hours (14:00-16:32 UTC), the Search results page was unavailable on many wikis (except for English Wikipedia). On Wikimedia Commons the search suggestions feature was unresponsive as well.

On 10 November, as part of verifying a bug report, a developer submitted a high volume of search queries against the active production Cirrus cluster (eqiad cirrussearch) via a tunnel from their local mw-vagrant environment. vagrant provision was (probably) later run without the tunnel being properly closed first, which resulted in (for reasons not yet understood) the deletion and recreation of the commonswiki_file_1623767607 index.

As a direct consequence, any Elasticsearch queries that targetted media files from commonswiki encountered a hard failure.

During the incident, all media searches on Wikimedia Commons failed. Wikipedia projects were impacted as well,[1] through the "cross-wiki" feature of the sidebar on Search results pages. This cross-wiki feature is enabled on most wikis by default, though notably not on English Wikipedia where the community disabled search integration to Commons.

Note that the search suggestions feature, as present on all article pages was not affected (except on Wikimedia Commons itself). The search suggestions field is how how most searches are performed on Wikipedia, and was not impacted. Rather, it impacted the dedicated Search results page ("Special:Search", which consistently failed to return results on wikis where the rendering of that page includes a sidebar with results from Wikimedia Commons.

Impact: For about 2.5 hours (14:00-16:32 UTC), the Search results page was unavailable on many wikis (except for English Wikipedia). On Wikimedia Commons the search suggestions feature was unresponsive as well.

Timeline

15:21 First ticket filed by impacted user https://phabricator.wikimedia.org/T295478

15:28 Additional, largely duplicate ticket filed by user https://phabricator.wikimedia.org/T295480

15:32 <Dylsss> Searching for files on Commons is currently impossible, I believe this is quite critical given the whole point of Commons is being a file repository

15:52 Initial attempt to shift cirrussearch traffic to codfw (did not work due to missing a required line in patch) (https://sal.toolforge.org/log/05mNCn0B1jz_IcWuO9iw)

16:32 Search team operator successfully moves all cirrussearch traffic to codfw, resolving user impact (https://sal.toolforge.org/log/8p2xCn0Ba_6PSCT9sorW)

??? (In future) Index successfully restored, and traffic is returned to eqiad

References:

Scorecard

Incident Engagement™  ScoreCard Score Notes
People Were the people responding to this incident sufficiently different than the previous N incidents? (0/5pt) 0 NA
Were the people who responded prepared enough to respond effectively (0/5pt) 5
Did fewer than 5 people get paged (0/5pt)? 0 NA
Were pages routed to the correct sub-team(s)? 0 No pages logged, issue reported via task
Were pages routed to online (working hours) engineers (0/5pt)? (score 0 if people were paged after-hours) 0 No pages logged
Process Was the incident status section actively updated during the incident? (0/1pt) 1
If this was a major outage noticed by the community, was the public status page updated? If the issue was internal, was the rest of the organization updated with relevant incident statuses? (0/1pt) 0
Is there a phabricator task for the incident? (0/1pt) 1
Are the documented action items assigned?  (0/1pt) 0
Is this a repeat of an earlier incident (-1 per prev occurrence) 0
Is there an open task that would prevent this incident / make mitigation easier if implemented? (0/-1p per task) 0
Tooling Did the people responding have trouble communicating effectively during the incident due to the existing or lack of tooling? (0/5pt) 0
Did existing monitoring notify the initial responders? (1pt) 0
Were all engineering tools required available and in service? (0/5pt) 5
Was there a runbook for all known issues present? (0/5pt) 0
Total Score 12

Actionables

  • Future one-off debugging of the sort that triggered this incident, when it requires production data, should be done on cloudelastic, which is an up-to-date read-only Elasticsearch cluster. If production data is needed but <= 1 week stale data is acceptable, relforge should be used instead.