Cases2 cases

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1. IL-0508 All SourceHut services went down when the main database server remilia.sr.ht failed in hardware and became unreachable

   SourceHut2023

   Symptoms

   At about 13:40 UTC on 11 January 2023, alerts started firing for most SourceHut services being unavailable, along with one for remilia.sr.ht, the physical host that is SourceHut's main database server. The database server could not be reached remotely at all.

   Service outage

   Trigger

   remilia.sr.ht, the main database server, suffered a hardware failure at about 13:38 UTC.

   Root cause

   Hardware failure

   Component

   Database

   Contributing factor

   Single point of failureLimited debug access

   Detection

   Alerts fired at about 13:40 UTC for most services and for remilia.sr.ht itself, after Prometheus started failing to scrape remilia at 13:38.

   Remediation

   • Sent SourceHut's emergency on-call contact in the datacenter area to go on site
   • Moved remilia's disks into the chassis of build worker cirno1.sr.ht and brought it online as remilia

   Action items

   • Make the off-site database copy able to serve as a failover database host
   • Re-prioritize the migration to the EU
   • Set up new database failover
   • Add a new EU build worker to backfill build capacity
   • Record a better hardware inventory for future reference

   View case
2. IL-0370 Render Postgres databases in Frankfurt were down up to 65 minutes as their disks stayed attached to a failed node

   Render2022

   Symptoms

   At 08:30 UTC on 23 May 2022, every user Postgres database on one node in Render's Frankfurt region went completely down after the node, supplied by Render's external cloud provider, had a hardware issue and failed its status check. The database instances could not start on a healthy node because their disks were still attached to the failed node.

   Service outageStorage disconnected or stale mounts

   Trigger

   A node supplied by Render's external cloud provider had a hardware issue and failed its status check at 08:30 UTC on 23 May 2022.

   Root cause

   Hardware failure

   Component

   DatabaseCloud block storage

   Contributing factor

   Single point of failure

   Detection

   An alert that fires when databases have been stuck in one state while starting up for at least 15 minutes paged the on-call engineer automatically at 08:57 UTC.

   Remediation

   • Manually terminated the failed node at about 09:27 UTC so the disks could attach to healthy nodes

   Action items

   • Create an alert that fires sooner than the current 15-minute startup alert
   • Make it easier to identify the correct corrective action, and eventually automate it
   • Review incident procedures so the status page reflects reliability accurately
   • Build high availability for Postgres so a primary's node hardware failure causes minimal downtime

   Lessons

   Hardware issues are rare but expected, so Render's mitigations aim at detecting them sooner and shortening the time to resolve them.

   View case

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