Cases3 cases

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1. IL-0200 Newly provisioned Kubernetes nodes ran an incompatible etcd version and broke cluster consensus in several GitHub production clusters, causing 5XX errors on Git operations and page loads

   GitHub2026

   Symptoms

   From 01:36 UTC on 12 March 2026, GitHub.com returned elevated error rates for Git operations, web requests and related services. At 01:54 UTC the GitHub status page said it was investigating reports of impacted performance for some services.

   High error rate

   Trigger

   During a planned infrastructure upgrade, a configuration issue made newly provisioned Kubernetes nodes run an incompatible version of etcd.

   Root cause

   Configuration change

   Component

   etcd

   Contributing factor

   Monitoring blind spot

   Detection

   The status page opened the incident at 01:54 UTC, 18 minutes after errors began, citing reports of impacted performance.

   Remediation

   • paused deployments for the duration of the incident
   • identified the newly provisioned nodes running the incompatible etcd version and removed them, which restored cluster consensus
   • ran a validation deploy that confirmed all systems were healthy before resuming normal operations

   Action items

   • Enforce version compatibility programmatically during node replacements
   • Add monitoring that detects split-brain conditions earlier
   • Update the recovery tooling to reduce restoration time

   View case
2. IL-0201 A framework upgrade caused kernel panics in GitHub's Kubernetes infrastructure, and GitHub.com web and API requests, mostly for issues and pull requests, failed intermittently for about 16 hours

   GitHub2025

   Symptoms

   From 18:05 UTC on March 17, 2025, GitHub.com web and API requests failed now and then for a small percentage of users, mostly requests about issues and pull requests. At 18:39 UTC the status page reported degraded performance for Issues.

   High error rateIntermittent timeouts

   Trigger

   A framework upgrade rolled out to GitHub's Kubernetes infrastructure caused kernel panics.

   Root cause

   Breaking change in an upgrade

   Component

   Linux kernel

   Contributing factor

   –

   Detection

   The status page opened the incident at 18:39 UTC, 34 minutes after the failures began, as an investigation of reports of degraded performance for Issues.

   Remediation

   • Downgraded the framework upgrade that caused the kernel panics
   • Disabled the problematic feature of the framework

   Action items

   • Investigate why the upgrade caused the kernel panics
   • Take steps to temporarily prevent the problem from coming back
   • Work out longer-term patch plans
   • Improve observability so that similar classes of problems can be reacted to quickly

   View case
3. IL-0199 A non-essential container exceeding its memory limit made GitHub's production pods unavailable, and their restarts failed because a DNS maintenance change had left the clusters unable to reach the image registry

   GitHub2020

   Symptoms

   At 08:18 UTC on 13 July 2020, production Kubernetes pods began to be marked unavailable. The loss of pods spread through the clusters and reduced capacity until GitHub.com services went down.

   OOMKilledImage pull failuresService outage

   Trigger

   A container in the production pods exceeded its memory limit and was terminated; a routine DNS maintenance operation completed earlier had left the clusters unable to reach the image registry.

   Root cause

   DNS or network fault

   Component

   Container memory limitContainer registry and its credentials

   Contributing factor

   Overlapping failuresHarmful manual actionSingle point of failure

   Remediation

   • restarted the process with the cached DNS records so the clusters could reach the registry
   • fetched the container images, redeployed and recovered the services

   Action items

   • Improve monitoring so pod restarts cannot fail again in the same pattern
   • Minimise the dependency on the image registry
   • Expand validation during DNS changes
   • Re-evaluate all existing Kubernetes deployment policies
   • Improve progressive deployments so the impact of a deployment can be evaluated incrementally

   Lessons

   A container that production traffic does not need can still take pods out of service, because a pod is available only when all of its containers are healthy. ImagePullPolicy Always turns every container restart into a registry dependency, so an unrelated DNS change that breaks registry access turns a one-minute self-healing event into a long outage, and a mass redeploy spreads it.

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