Cases14 cases

6 to 10 of 14

1. IL-0121 A faulty code change to a control plane cluster meant for low-priority workloads degraded the production inference workloads it also managed

   OpenAI2025

   Symptoms

   Between 2:10 PM and 3:05 PM PDT on July 9, 2025, success rates of the gpt-4.1-mini model in the API dropped for about 20 minutes, and ChatGPT search returned many more errors than usual for about 35 minutes.

   High error rate

   Trigger

   A faulty code change was deployed to a control plane cluster whose main job is managing low-priority workloads.

   Root cause

   Faulty deployment

   Component

   –

   Contributing factor

   Excessive blast radiusNo safeguard on destructive change

   Remediation

   • rolled back the faulty code change

   Action items

   • Add safeguards that prevent production inference workloads from being managed by the low-priority control plane cluster
   • Strengthen testing for deploying high-impact control plane changes
   • Move all existing production inference workloads under the production control plane cluster
   • Build a circuit breaker that stops large-scale unintended changes

   View case
2. IL-0020 During an EKS 1.30 upgrade the descheduler tried to reschedule every pod on the cordoned nodes at once and production workloads went down

   UK Ministry of Justice2025

   Symptoms

   At 09:36 on 18 March 2025, during the upgrade of the live cluster to EKS 1.30, users reported that their pods were being terminated and were not restarting automatically, in both production and non-production environments. Automated infrastructure alerts fired as well, and production services had outages.

   Pod evictionPods PendingService outageUpgrade stall

   Trigger

   Upgrading the live EKS cluster from 1.29 to 1.30, during which the descheduler attempted to reschedule all pods on the cordoned nodes simultaneously.

   Root cause

   Faulty deployment

   Component

   DeschedulerNode poolCluster autoscaler

   Contributing factor

   No headroomNo alert on limitUnreviewed defaults

   Detection

   Users reported at 09:36 that pods were being terminated and not restarting, and automated infrastructure alerts fired.

   Remediation

   • Removed the cordon annotation so pods could be rescheduled
   • Deleted stuck 1.30 nodes to force their recreation
   • Added a new node group of 20 nodes running 1.30 by hand
   • Cordoned and drained all old 1.29 nodes onto the new 1.30 nodes

   Action items

   • Raise an AWS Production System Down support case (Case ID: 174229643100496)
   • Get guidance from AWS support on querying control-plane logs to find the root cause of similar issues
   • Document a runbook for emergency scaling of a new node group in case of unexpected capacity shortages
   • Alert on an imbalance between the autoscaling group and the Kubernetes nodes
   • Review the descheduler configuration to understand why it throws pods off cordoned nodes, and fix it where possible
   • Alert on spikes in the pending pod count

   Lessons

   The write-up lists review actions rather than lessons. They show the team had no documented way to add an emergency node group, no alert on a mismatch between the autoscaling group and the nodes Kubernetes sees, no alert on a spike in pending pods, and no clear understanding of how the descheduler treats cordoned nodes.

   View case
3. IL-0142 GKE clusters on 1.24 and later wrote unexpected fluentbit error entries such as "Failed to get record: decoder: failed to decode payload: EOF" that used up the Logging API write quota for some customers

   Google Cloud2023

   Symptoms

   From 07:13 US/Pacific on 6 July 2023, GKE customers saw unexpected additional error and warning entries in their cluster logs, written to the Cloud Logging project that holds the clusters. Standard and Autopilot clusters at GKE 1.24.x and later were affected.

   Log flood

   Trigger

   Google rolled out a new version of the GKE component that processes logs (preliminary analysis).

   Root cause

   Faulty deployment

   Component

   Telemetry agent

   Contributing factor

   –

   Remediation

   • gave customers a workaround: request a Logging API quota increase, or apply a log exclusion for the fluentbit-gke messages
   • rolled out a fix gradually to the affected clusters between 10 and 18 July 2023

   Lessons

   Log messages written by a managed logging agent count against the customer's own Logging API write quota and logging bill, so a faulty agent release can drop a customer's other logs. A log exclusion on the agent's container name and the message patterns keeps the noise out of storage until a fix arrives.

   View case
4. IL-0163 An API change that slipped through a gap in automated testing made LKE clusters resize to the wrong number of nodes and added billable worker nodes to customer accounts

   Linode2023

   Symptoms

   Resizing an LKE cluster produced an incorrect number of nodes, so some customer clusters were resized in unexpected ways and the extra worker nodes were billed to the customer accounts. The clusters themselves kept functioning. Linode's first status update, at 05:07 UTC on 1 June 2023, advised customers to avoid resizing their clusters if possible.

   Autoscaler misbehaviour

   Trigger

   At about 16:00 UTC on 31 May 2023 a change to the API that caused LKE clusters to scale improperly was pushed to production.

   Root cause

   Faulty deployment

   Component

   Node pool

   Contributing factor

   Gap in automated tests

   Detection

   The first status update, at 05:07 UTC on 1 June, said Linode had been made aware of an issue when resizing LKE clusters, about 13 hours after the change went out.

   Remediation

   • advised customers to avoid resizing their clusters
   • deployed a hotfix at 09:40 UTC on 1 June that corrected the scaling behaviour
   • left the extra worker nodes in place to avoid disrupting customer workloads
   • contacted affected customers by ticket about credit adjustments and further mitigation

   Action items

   • Audit the automated tests
   • Add pre-deployment checklist items so the same failure does not happen again

   Lessons

   An API change that alters scaling behaviour resized customer clusters and added cost while the clusters themselves kept working; Linode announced the issue about 13 hours after the change went out. Removing the extra nodes would have disrupted workloads, so the cost was handled through credits instead.

   View case
5. IL-0164 An incremental Linode Kubernetes Engine production update that was missing changes from the previous release made cluster upgrades and node additions fail silently

   Linode2022

   Symptoms

   From about 18:30 UTC on June 15, 2022, customers of the Linode Kubernetes Engine (LKE) who tried to upgrade a cluster or add nodes saw those operations fail silently, without an error. The status page opened an investigation of an LKE issue at 19:54 UTC, and the affected list covered LKE in eleven regions.

   Upgrade stall

   Trigger

   An incremental update pushed to the LKE production environment at about 18:30 UTC.

   Root cause

   Faulty deployment

   Component

   Node pool

   Contributing factor

   –

   Detection

   The status page began investigating at 19:54 UTC, 1 hour 24 minutes after the update.

   Remediation

   • Released a follow-up LKE update at about 21:00 UTC that contained the missing changes

   Action items

   • Add steps and automation to the update process

   View case

By root cause1