Incidents/2022-12-12 wdqs codfw brief outage
document status: draft
Summary
| Incident ID | 2022-12-12 wdqs codfw brief outage | Start | 2022-12-12 20:14:17 |
|---|---|---|---|
| Task | End | 2022-12-12 20:30:00 | |
| People paged | 3 | Responder count | 1 |
| Coordinators | 1 | Affected metrics/SLOs | WDQS Uptime SLO |
| Impact | For about 15 minutes, wdqs queries routed to codfw failed | ||
A large influx in requests led to excessive thread pool usage from codfw blazegraph backends, with concomitant increases in CPU load and throttling filter state size. This triggered a known bug in Blazegraph where its improper thread management leads to deadlock.
The system self healed, perhaps due to application-level throttling state throttling the offender.
Most or all CODFW-routed wdqs requests during the incident window failed.
Timeline
Beginning of incident
2022-12-12 20:13:18 <+jinxer-wm> (ProbeDown) firing: Service wdqs-ssl:443 has failed probes (http_wdqs-ssl_ip4) #page - https://wikitech.wikimedia.org/wiki/Runbook#wdqs-ssl:443 - https://grafana.wikimedia.org/d/O0nHhdhnz/network-probes-overview?var-job=probes/service&var-module=All - https://alerts.wikimedia.org/?q=alertname%3DProbeDown
2022-12-12 20:13:18 <+jinxer-wm> (ProbeDown) firing: Service wdqs-ssl:443 has failed probes (http_wdqs-ssl_ip4) - https://wikitech.wikimedia.org/wiki/Runbook#wdqs-ssl:443 - https://grafana.wikimedia.org/d/O0nHhdhnz/network-probes-overview?var-job=probes/service&var-module=All - https://alerts.wikimedia.org/?q=alertname%3DProbeDown
2022-12-12 20:14:17 <+icinga-wm> PROBLEM - PyBal backends health check on lvs2009 is CRITICAL: PYBAL CRITICAL - CRITICAL - wdqs-heavy-queries_8888: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs2004.codfw.wmnet, wdqs2002.codfw.wmnet are marked down but pooled: wdqs-ssl_443: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs2004.codfw.wmnet, wdqs2002.codfw.wmnet are marked down but pooled: wdqs_80: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs20
2022-12-12 20:14:17 <+icinga-wm> .wmnet, wdqs2002.codfw.wmnet are marked down but pooled https://wikitech.wikimedia.org/wiki/PyBal
2022-12-12 20:14:17 <+icinga-wm> PROBLEM - WDQS SPARQL on wdqs2001 is CRITICAL: CRITICAL - Socket timeout after 10 seconds https://wikitech.wikimedia.org/wiki/Wikidata_query_service/Runbook
2022-12-12 20:14:17 <+icinga-wm> PROBLEM - WDQS SPARQL on wdqs2003 is CRITICAL: CRITICAL - Socket timeout after 10 seconds https://wikitech.wikimedia.org/wiki/Wikidata_query_service/Runbook
2022-12-12 20:25:00 Rough end of incident (end of user impact)
2022-12-12 20:31:00 [WDQS] ryankemper@cumin2002:~$ sudo -E cumin -b 4 wdqs2* 'systemctl restart wdqs-blazegraph' By this point, the service had already recovered, but was restarted out of an abundance of caution.
Detection
The issue was rapidly detected by pybal monitoring of WDQS. A page was emitted by the monitoring system fairly quickly.
2022-12-12 20:13:18 <+jinxer-wm> (ProbeDown) firing: Service wdqs-ssl:443 has failed probes (http_wdqs-ssl_ip4) #page - https://wikitech.wikimedia.org/wiki/Runbook#wdqs-ssl:443 - https://grafana.wikimedia.org/d/O0nHhdhnz/network-probes-overview?var-job=probes/service&var-module=All - https://alerts.wikimedia.org/?q=alertname%3DProbeDown
2022-12-12 20:13:18 <+jinxer-wm> (ProbeDown) firing: Service wdqs-ssl:443 has failed probes (http_wdqs-ssl_ip4) - https://wikitech.wikimedia.org/wiki/Runbook#wdqs-ssl:443 - https://grafana.wikimedia.org/d/O0nHhdhnz/network-probes-overview?var-job=probes/service&var-module=All - https://alerts.wikimedia.org/?q=alertname%3DProbeDown
2022-12-12 20:14:17 <+icinga-wm> PROBLEM - PyBal backends health check on lvs2009 is CRITICAL: PYBAL CRITICAL - CRITICAL - wdqs-heavy-queries_8888: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs2004.codfw.wmnet, wdqs2002.codfw.wmnet are marked down but pooled: wdqs-ssl_443: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs2004.codfw.wmnet, wdqs2002.codfw.wmnet are marked down but pooled: wdqs_80: Servers wdqs2003.codfw.wmnet, wdqs2001.codfw.wmnet, wdqs20
2022-12-12 20:14:17 <+icinga-wm> .wmnet, wdqs2002.codfw.wmnet are marked down but pooled https://wikitech.wikimedia.org/wiki/PyBal
Conclusions
OPTIONAL: General conclusions (bullet points or narrative)
What went well?
- …
OPTIONAL: (Use bullet points) for example: automated monitoring detected the incident, outage was root-caused quickly, etc
What went poorly?
- …
OPTIONAL: (Use bullet points) for example: documentation on the affected service was unhelpful, communication difficulties, etc
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
- The wdqs codfw dashboard shows a large spike in queries for wdqs2*, with a corresponding increase in CPU load and the throttling filter state.
Actionables
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) | |||