Incident Library
Applied filters Root causeSoftware defectComponentCloud load balancerSymptomNetwork unreachableClear allEvery case under the filters, with no sentence; newest first.
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Cases2 cases

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  1. IL-0529 New Google Cloud VMs and other instances came up without network connectivity in all zones after VPC controllers stopped
    Google Cloud2024
    Symptoms

    From 15:22 US/Pacific on 16 May 2024, new VMs and other new instances across Google Cloud came up without network programming, so the new instances could not open network connections, and VMs that were migrated or restarted lost connectivity. Changes to virtual network configuration, such as firewall rules and load balancers, were not applied. Internal monitoring alerted Google engineers at 15:41.

    Network unreachablePacket lossCluster or node provisioning stallScale-up failureHigh error rate
    Trigger

    Google's infrastructure team ran a routine maintenance action meant to shut down one unused VPC Controller in a single Google Cloud zone, and the automation shut down VPC controllers in all zones where the controllers were still in use.

    Root cause
    Software defect
    Component
    Network control plane (SDN)Cloud load balancerNAT gateway
    Contributing factor
    Change with a delayed effectIgnored early signalNo safeguard on destructive changeExcessive blast radius
    Detection

    Internal monitoring alerts reached Google engineers at 15:41 US/Pacific, and the investigation started immediately.

    Remediation
    • Paused maintenance operations to prevent the shutdown from repeating
    • Brought the affected VPC Controllers back into a serving state in every zone
    • Stopped the automation responsible for the shutdown until safeguards are in place
    • Recovered partial Apigee proxy deployments by hand
    • Cleaned up VMs left behind by failed Dataproc cluster deletions
    Action items
    • Add safety measures that check that maintenance operations carry correctly scoped zone information
    • Make the underlying tools reject maintenance operations that do not specify zones
    • Tighten on-demand access control so one maintenance invocation cannot work across multiple zones
    • Add safety checks, testing and validation for maintenance operations, including positive and negative test cases for the new safety measures
    View case
  2. IL-0396 New or live-migrated GCE instances, VPN tunnels and network load balancers were unreachable on public IPs for over 2h
    Google Cloud2017
    Symptoms

    On 30 January 2017, Google Compute Engine instances, Cloud VPN tunnels and GCE network load balancers that were created or live migrated between 10:36 and 12:42 PDT could not be reached on their public IP addresses. Resources created earlier, and instances that were not live migrated, kept working.

    Network unreachableProbe failures
    Trigger

    A large set of updates was applied to a rarely used load balancing configuration on the shared layer 2 load balancers.

    Root cause
    Software defect
    Component
    Cloud load balancerNetwork control plane (SDN)
    Contributing factor
    Excessive blast radiusGap in automated tests
    Remediation
    • Restarted the jobs that program changes into the network load balancers, so the stuck changes were processed as a batch
    • Applied the fix zone by zone between 11:36 and 12:42
    Action items
    • Increase the canary timeout so updates that hit the inefficient code path only slow network changes instead of stopping them
    • Improve the inefficient code path
    • Write new tests that check behaviour on a wider range of configurations
    • Accelerate replacing global propagation of address configuration with decentralized routing
    • Add metrics and alerting that identify this kind of issue sooner
    View case
Check your cluster for this

These 2 cases involve Cloud load balancer and Network control plane (SDN). 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 cause1

Software defect2 cases

Component
Cloud load balancer2Network control plane (SDN)2NAT gateway1
Contributing factor
Excessive blast radius2Change with a delayed effect1Ignored early signal1No safeguard on destructive change1Gap in automated tests1
Organisation
Google Cloud2
  1. IL-0529 New Google Cloud VMs and other instances came up without network connectivity in all zones after VPC controllers stopped
    Google Cloud2024
  2. IL-0396 New or live-migrated GCE instances, VPN tunnels and network load balancers were unreachable on public IPs for over 2h
    Google Cloud2017