Incident Library
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  • Root cause
  • Component
  • Symptom
  • Contributing factor
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Cases8 cases

8 to 8 of 8

  1. IL-0108 An Alcide admission controller applied to the production cluster during a workshop made create and update requests on Deployments time out
    DFDS2020
    Symptoms

    At 14:41 CET on 4 November 2020 users reported timeouts when deploying to Hellman, the production Kubernetes cluster. The timeouts were confirmed at 15:04.

    Deploys failingControl plane lag
    Trigger

    During an Alcide workshop that began at 13:00 CET, an Alcide admission controller was applied to the production cluster at 13:13 in the belief that it would not disrupt anything.

    Root cause
    Configuration change
    Component
    Admission webhookKubernetes API server
    Contributing factor
    No configuration testsUnverified assumptionMonitoring blind spot
    Detection

    Users reported timeouts when deploying to the Hellman cluster at 14:41 CET; the timeouts were verified at 15:04.

    Remediation
    • toggled the Alcide admission controller to verify that it caused the timeouts
    • permanently deleted the Alcide admission controller
    Action items
    • Monitor Kubernetes deployments for timeouts
    • Monitor 5xx status codes from the Kubernetes API server
    Lessons

    New components are applied in sandbox clusters, not in production. The team needs enough Alcide knowledge to maintain the component until it is fully deprecated.

    View case
Check your cluster for this

These 8 cases involve Cloud load balancer and Terraform. kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

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By root cause4

Capacity exhaustion1 case

Component
Application databaseContainer memory limitTelemetry agent
Contributing factor
Excessive blast radiusHarmful manual actionMonitoring blind spotNo resource requests or limits
Organisation
DFDS
  1. IL-0110 A Grafana Agent pod's high memory use and crash-looping Hangfire pods drove a Kubernetes node into system OOM and NotReady, twice in one day
    DFDS2024

Configuration change4 cases

Component
Cloud load balancer2Terraform2Admission webhook1Container runtime1Ingress controller1Kubernetes API server1Node launch template1Node pool1Telemetry agent1AWS VPC CNI1
Contributing factor
No configuration tests3Unverified assumption2Monitoring blind spot2Automation amplification1Unreviewed defaults1Harmful manual action1No runbook1Missed in review1Unrepresentative staging1
Organisation
DFDS4
  1. IL-0109 A retried node rollover on a DFDS EKS cluster set the Auto Scaling group back to 15 instances, and the default termination policy removed every healthy worker node, leaving the cluster with no nodes
    DFDS2023
  2. IL-0111 Switching the main Kubernetes ingress controller from Traefik v1 to v2 stopped X-Forwarded headers being passed, which broke the Okta login flow for every service using Okta and stopped DFDS online bookings for over an hour
    DFDS2021
  3. IL-0105 Replacing the AWS VPC CNI during a Terraform refactoring detached the ALB target groups, and every service in the Kubernetes cluster returned 503
    DFDS2021
  4. IL-0108 An Alcide admission controller applied to the production cluster during a workshop made create and update requests on Deployments time out
    DFDS2020

Software defect2 cases

Component
Cloud load balancer1Ingress controller1kubelet1Node launch template1Linux kernel1Node operating system image1Terraform1AWS VPC CNI1
Contributing factor
Automation amplification1Excessive blast radius1Change with a delayed effect1Monitoring blind spot1No configuration tests1No health probes1No staged rollout1Overlapping failures1
Organisation
DFDS2
  1. IL-0112 The daily node rollover put DFDS's EKS nodes on an AMI later recalled for a kernel issue, causing "PLEG is not healthy" NodeNotReady flaps and pod network timeouts
    DFDS2022
  2. IL-0106 A malformed Traefik IngressRoute triggered a Traefik v2 bug once a node rollover restarted every Traefik pod, and all Kubernetes services returned 404
    DFDS2021

Certificate or credential expiry1 case

Component
Admission webhookPolicy engine
Contributing factor
Unreviewed defaultsIgnored early signalMonitoring blind spotDeferred upgrades
Organisation
DFDS
  1. IL-0107 Kyverno stuck in a crash loop behind a webhook with failurePolicy fail blocked every change to Kubernetes Service objects for 88 minutes
    DFDS2022