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1. 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.

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