Fly.io Upstash Redis service distruption (FRA region)

Final update

On May 12th and 13th at various times, a subset of Upstash Redis instances on [Fly.io](http://Fly.io) experienced intermittent hangs and elevated error rates. The Redis process would stall inside a logging syscall , alive but not making progress , which made the issue hard to spot from our usual telemetry. After investigating with Fly's team, we identified the root cause as a bad interaction between a recent guest kernel update on Fly's newer machines and an upstream Cloud Hypervisor bug \([cloud-hypervisor#7672](https://github.com/cloud-hypervisor/cloud-hypervisor/issues/7672)\) affecting log writes from inside the VM. We mitigated by disabling the affected logging paths, and Fly has since rolled out a hypervisor-side patch, fully resolving the issue. No data was lost. Sorry for the disruption.

1. Postmortem · May 15, 12:49 UTC
   On May 12th and 13th at various times, a subset of Upstash Redis instances on [Fly.io](http://Fly.io) experienced intermittent hangs and elevated error rates. The Redis process would stall inside a logging syscall , alive but not making progress , which made the issue hard to spot from our usual telemetry. After investigating with Fly's team, we identified the root cause as a bad interaction between a recent guest kernel update on Fly's newer machines and an upstream Cloud Hypervisor bug \([cloud-hypervisor#7672](https://github.com/cloud-hypervisor/cloud-hypervisor/issues/7672)\) affecting log writes from inside the VM. We mitigated by disabling the affected logging paths, and Fly has since rolled out a hypervisor-side patch, fully resolving the issue. No data was lost. Sorry for the disruption.
2. Resolved · May 11, 18:22 UTC
   The incident has been resolved. We are working with Fly team on RCA.
3. Investigating · May 11, 17:19 UTC
   We are working with Fly team to investigate the root cause.
4. Investigating · May 11, 15:07 UTC
   We are continuing to investigate the issue.
5. Investigating · May 11, 15:05 UTC
   Some databases may experience increased latency or timeouts in Fly.io’s FRA region.