IL-0329 incident.io · 2025-04-09database
A routine migration left PGAudit stuck holding Postgres locks, causing intermittent timeouts and a 2-minute outage
The weekend before the incident, incident.io upgraded its database to Postgres 17 and turned off the PGAudit extension during the upgrade. After testing in staging succeeded, PGAudit was turned back on in production and checked to be working. On Wednesday 9 April at 14:16 UTC a routine migration that created an empty table and added an index interacted with PGAudit in an unexpected way: the extension became unresponsive while holding critical locks. The locked resources blocked other database operations, which showed as intermittent slowness across the dashboard, mobile app, Slack app and API. Killing the PGAudit processes failed because they did not respond to timeout signals, and further kill attempts also failed as timeouts rose.
The team then chose to restart the database to end the stuck process by force, accepting a short hard outage instead of further disruption. The primary database was down for just under 2 minutes, from 14:25 to 14:27 UTC, and no on-call alerts or escalations were dropped during that time. After service was restored, PGAudit was disabled and then removed entirely so that it could not be switched back on by accident. The cause of the interaction between the migration and PGAudit was still under investigation when the write-up was published.
- Severity
- –
- Scope
- Intermittent slowness and timeouts across the dashboard, mobile app, Slack app and API from 14:16 to 14:27 UTC, including a primary database outage of just under 2 minutes; on-call alerts and escalations kept working
- Users affected
- –
- Region
- –
- Time to detect
- –
- Time to resolve
- 11m
Symptoms
On 9 April 2025 from 14:16 UTC, incident.io's dashboard, mobile app, Slack app and API became intermittently slow and requests timed out. Monitoring alerted the team soon after a routine migration began on the production Postgres database, and the incident ended with the primary database unavailable for just under 2 minutes, from 14:25 to 14:27 UTC.
The migration created an empty table and added an index. PGAudit, a Postgres extension for detailed logging of database activity and of changes to database structures and user permissions, stopped responding while it held critical database locks, and other database operations queued behind those locks. The first attempt was to kill the stuck PGAudit processes, but they ignored timeout signals, so the locks were never released and the timeouts kept climbing.
Symptom Lock contention or deadlockIntermittent timeoutsHigh latencyService outage
Root cause
Root cause Software defect
- Trigger
- At 14:16 UTC a routine migration that created an empty table and added an index ran on the production database, where PGAudit had been re-enabled after the weekend upgrade to Postgres 17.
Detection
incident.io's monitoring alerted the team to the problem shortly after the migration started.
Remediation
- Restarted the primary database to force the stuck PGAudit process to end, taking just under 2 minutes of downtime
- Disabled and then fully removed the PGAudit extension after service was restored
Action items
- Keep PGAudit removed until its safety can be guaranteed
- Continue investigating the interaction between the migration and PGAudit
- Hold an internal debrief of the incident
- Improve processes and monitoring to detect, prevent and respond to similar situations
Lessons
–
Sources
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