Incident Library
  • Root cause
  • Component
  • Symptom
  • Contributing factor
  • Case

Cases62 cases

20 to 24 of 62

  1. IL-0119 ChatGPT web service pods crash-looped on failing health checks after a Cosmos DB failure, leaving too few healthy pods to serve the web layer
    OpenAI2025
    Symptoms

    From 3:30am to 7:08am PT, chatgpt.com and a small number of OpenAI APIs returned elevated error rates. The status page classed the incident as a full outage.

    High error rateContainer crash loopProbe failures
    Trigger

    A failure of Cosmos DB in ChatGPT, at OpenAI's service provider.

    Root cause
    Cloud provider outage
    Component
    Database
    Contributing factor
    Health check tied to a dependency
    Remediation
    • the service provider recovered the affected Cosmos DB databases at 4:25am PT
    • fixed the web server's health checking logic, which ended the pod crash loop
    Action items
    • Change the web systems to degrade more gracefully when they fail, including concurrency control and better load shedding
    • Make the database layer more resilient to service provider outages (described as already underway)
    Lessons

    The database came back at 4:25am PT, yet users saw errors until 7:08am PT: the web tier's own health checks kept removing pods after the dependency had recovered. The planned changes target the web tier's behaviour under failure, with concurrency control and load shedding, rather than the database alone.

    View case
  2. IL-0204 An etcd memory spike overloaded the control plane of a Render Frankfurt cluster, and DNS then failed because CoreDNS ran on the rebooted control plane nodes and could not start without the API server
    Render2024
    Symptoms

    In January 2022 an etcd memory spike overloaded the Kubernetes control plane of one of Render's clusters in Frankfurt. At first only operations that need the control plane failed: new deploys and cron job runs.

    Control plane unresponsiveDeploys failingDNS resolution failuresHigh error rate
    Trigger

    A memory spike in etcd overloaded the cluster's control plane.

    Root cause
    Capacity exhaustion
    Component
    etcdCoreDNSKubernetes API server
    Contributing factor
    Unreviewed defaultsHarmful manual action
    Action items
    • Run CoreDNS on data plane nodes instead of control plane nodes
    • Run etcd on dedicated nodes
    Lessons

    CoreDNS can keep answering from its in-memory cache while the API server is down, but it cannot initialise without it. With CoreDNS on the control plane nodes, a reboot or restart during a control plane outage turned a failure of deploys and cron jobs into a failure of requests to services that were already running. The core problem was that the data plane was not isolated enough from the control plane: even without the reboot, the etcd memory spike alone could have forced CoreDNS to restart.

    View case
  3. IL-0005 A new telemetry service overloaded the Kubernetes API servers of large clusters and broke DNS-based service discovery for all OpenAI services
    OpenAI2024
    Symptoms

    Alerts fired at 3:13 PM PST on 11 December 2024, and from 3:16 PM every OpenAI service was significantly degraded or completely unavailable, including ChatGPT, the API and Sora. The status page reported API calls returning errors and difficulties logging in to platform.openai.com and ChatGPT. Customer impact peaked at 3:40 PM.

    Service outageHigh error rateControl plane unresponsiveDNS resolution failures
    Trigger

    At 2:23 PM PST a change introducing a new telemetry service, which collects detailed Kubernetes control plane metrics, was merged and the deployment pipeline started. Between 2:51 PM and 3:20 PM the change was applied to all clusters.

    Root cause
    Configuration change
    Component
    Kubernetes API serverClient-side DNS resolver and cacheTelemetry agent
    Contributing factor
    Unrepresentative stagingNo staged rolloutCache-masked failureMonitoring blind spotLimited debug access
    Detection

    OpenAI's detection tools worked: alerts fired at 3:13 PM PST, a few minutes before customer impact began at 3:16 PM, and the root cause was identified at 3:16 PM.

    Remediation
    • Scaled clusters down to reduce the total Kubernetes API load
    • Blocked network access to the Kubernetes admin APIs so no new expensive requests arrived
    • Scaled up the Kubernetes API servers
    • Removed the telemetry service once enough control was back
    • Moved traffic from impacted clusters to healthy ones
    • Intervened manually in clusters where simultaneous resource downloads saturated resource limits
    Action items
    • Put every infrastructure configuration change through a phased rollout with continuous monitoring of both the service workloads and the clusters, including the Kubernetes control plane
    • Run fault injection tests in which the data plane runs without the control plane for longer, and tests that roll out bad changes on purpose to check detection and rollback
    • Build break-glass mechanisms so engineers can reach the Kubernetes API servers in any circumstances
    • Decouple the Kubernetes data plane from the control plane so that service discovery for critical workloads does not depend on the control plane
    • Speed up recovery with better caching and dynamic rate limiters for resources needed at cluster startup, and regular drills that rapidly replace an entire cluster
    Lessons

    Several systems and processes failed at once and interacted in unexpected ways: tests did not catch the change's effect on the Kubernetes control plane, DNS caching put a delay between the change and the failures, and being locked out of the control plane made remediation very slow. Because service discovery used Kubernetes DNS, the control plane was carrying load for product traffic even though the data plane was meant to be independent of it.

    View case
  4. IL-0118 A global change to Kubernetes namespace labels made the networking layer recompute metadata and overwhelmed the control planes of three of OpenAI's largest GPU clusters
    OpenAI2024
    Symptoms

    From 10:15 am PT on 25 November 2024 a large share of both API and ChatGPT traffic failed with timeouts and 503 errors.

    High error rateHigh latencyControl plane unresponsive
    Trigger

    A global change to Kubernetes namespace labels caused the networking layer to recompute metadata. The change had rolled out to the small clusters without problems.

    Root cause
    Configuration change
    Component
    Kubernetes API server
    Contributing factor
    Excessive blast radiusLimited debug access
    Remediation
    • moved workloads out of the impacted clusters by hand
    • with the cloud provider, scaled up the number of control plane nodes while scaling down the number of data plane nodes, which let the control planes recover
    Action items
    • Lock namespace changes so this incident cannot recur
    • Freeze certain types of infrastructure deploys
    • Allowlist identities to prevent a recurrence of this class of incidents
    • Improve the GPU load balancing logic so traffic is re-routed automatically and more effectively when possible
    • Improve change management for fleet-wide infrastructure changes
    View case
  5. IL-0232 Calico pods in the codfw WikiKube cluster hit their resource limits and crash-looped, taking nodes out one by one
    Wikimedia Foundation2024
    Symptoms

    At 05:01 UTC on 9 October 2024 a page fired for GatewayBackendErrorsHigh, elevated 5xx errors from page-analytics_cluster in codfw, followed by a growing number of KubernetesCalicoDown alerts for WikiKube nodes not running the calico-node pod and by MediaWikiMemcachedHighErrorRate. For about an hour uncached MediaWiki requests, such as those of logged-in users, edits and API calls, saw high latency or errors.

    High error rateHigh latencyContainer crash loopProbe failuresControl plane lag
    Trigger

    An operator used the new mwscript-k8s utility to run a batch of video transcode maintenance, the TimedMediaHandler requeueTranscodes.php script. mwscript-k8s deploys a whole helm release for every script invocation, so the batch created close to 2k Calico NetworkPolicies along with many other resources over several hours.

    Root cause
    Capacity exhaustion
    Component
    CalicoHelmJobs and CronJobs
    Contributing factor
    Change with a delayed effectNo runbook
    Detection

    Automated monitoring detected the issue and paged the on-call SRE: GatewayBackendErrorsHigh at 05:01:36 UTC, 16 KubernetesCalicoDown alerts at 05:03:32 UTC and MediaWikiMemcachedHighErrorRate at 05:04:15 UTC.

    Remediation
    • Raised the resource limits of the Calico and Typha pods and applied the change with helmfile, which redeployed all Calico pods
    Action items
    • Stop mwscript-k8s from creating so many resources
    Lessons

    The incident came close to a full outage. Automated monitoring caught it and many responders found the cause, but end users were affected and responders were unsure whether they could switch over to eqiad. The problem was noticed just before the hand-off from Americas to EMEA SRE shifts, a period with a long-known lack of coverage, and it helped that the transcodes were not queued on a Friday evening in the US.

    View case
Check your cluster for this

These 62 cases involve Database and Ingress controller. 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.

Open kubegap

By root cause10

Configuration change14 cases

Component
Cloud load balancer2Client-side DNS resolver and cache2Helm2Kubernetes API server2Pod priority and preemption2Telemetry agent2Argo CD1cert-manager1Cilium1Configuration templating1ConfigMaps and Secrets1conntrack table1Container runtime1CoreDNS1Database1etcd1external-dns1HAProxy1HTTP and RPC client library1Ingress controller1kubelet1Linux kernel1Application logging library1Container memory limit1Persistent volumes and stateful sets1Prometheus1Terraform1AWS VPC CNI1
Contributing factor
Monitoring blind spot5Unverified assumption4Excessive blast radius4Automation amplification3Change with a delayed effect3Limited debug access2No configuration tests2No staged rollout2Retry storm2Missed in review2Unreviewed defaults1Cache-masked failure1Unknown limit1No alert on limit1No resource requests or limits1No runbook1No safeguard on destructive change1No headroom1Partial rollout1Unrepresentative staging1
Organisation
OpenAI3Datadog1DFDS1GitHub1GitLab1Grafana Labs1InfluxData1LIFULL1MUSINSA1NU.nl1Pusher1Wikimedia Foundation1
  1. IL-0179 With DEBUG logging and synchronous log output, a high-traffic service filled the 64 KB stdout pipe, so request threads blocked in write() while holding database connections and HikariCP ran dry, failing requests in 30-second bursts
    MUSINSA2026
  2. 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
  3. IL-0122 An invalid value in a configuration shared by several ChatGPT services put pods into crash loops and raised error rates
    OpenAI2025
  4. IL-0005 A new telemetry service overloaded the Kubernetes API servers of large clusters and broke DNS-based service discovery for all OpenAI services
    OpenAI2024
  5. IL-0118 A global change to Kubernetes namespace labels made the networking layer recompute metadata and overwhelmed the control planes of three of OpenAI's largest GPU clusters
    OpenAI2024
  6. IL-0459 MediaWiki on Kubernetes terminated TLS with a wrong certificate after a deployment, and 1% of requests failed
    Wikimedia Foundation2023
  7. IL-0009 A duplicated generated name made Argo CD replace the InfluxDB Cloud production Application and delete the whole production environment
    InfluxData2022
  8. IL-0461 Every rollout of Datadog's metrics query service on Kubernetes raised errors that the logs blamed on DNS
    Datadog2022
  9. IL-0208 A GitLab chart bump that renamed Kubernetes Service and Deployment ports made the GCP load balancer reconfigure, and GitLab.com slowed down and returned intermittent 50x errors
    GitLab2022
  10. IL-0442 Older pods on LIFULL's KEEL Kubernetes cluster were preempted all at once and the external error rate spiked
    LIFULL2021
  11. 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
  12. IL-0004 A new default pod priority let a new Cortex cluster preempt every production ingester in a cascade, taking Grafana Cloud Hosted Prometheus down
    Grafana Labs2019
  13. IL-0066 Broken ConfigMap change lay dormant for weeks, then took down Pusher's edge proxy when a cluster upgrade replaced its pods
    Pusher2019
  14. IL-0035 Worker nodes went NotReady after a new ElastAlert rule without memory limits used up node memory
    NU.nl2019

Capacity exhaustion21 cases

Component
Database6CoreDNS4Kubernetes API server4Node pool4Container memory limit3Pod scheduling and placement3Cloud block storage2In-memory cache2CI system2Client-side DNS resolver and cache2etcd2Helm2Jobs and CronJobs2Persistent volumes and stateful sets2Calico1conntrack table1Container CPU limit1Credential broker for pods1GKE control plane1HAProxy1Horizontal pod autoscaler1Model inference server1Ingress controller1JupyterHub1kube-proxy1kubelet1Linux kernel1Managed Kubernetes control plane and provider API1Pod termination1Container registry and its credentials1Service discovery1Telemetry agent1
Contributing factor
Unreviewed defaults5Single point of failure5Unverified assumption4Unknown limit4Monitoring blind spot4No alert on limit4Retry storm4Excessive blast radius3Unrepresentative staging3Automation amplification2Change during peak hours2Change with a delayed effect2Harmful manual action2No capacity planning2No headroom2No caching1No resource requests or limits1No runbook1No staged rollout1Ineffective rollback1
Organisation
Zalando32i2c1Civis Analytics1CyberAgent1freedesktop.org1GitHub1GitLab1Google Cloud1Honeycomb1IONOS Cloud1loveholidays1Microsoft1MonotaRO1Moonlight1PostHog1RebelMouse1Render1UC Berkeley1Wikimedia Foundation1
  1. IL-0471 GitHub Actions runs failed or sat queued for 9 hours after a routine deployment's pod replacement saturated capacity
    GitHub2026
  2. IL-0435 Error rates rose as Aurora MySQL killed connections and declined queries to avoid OOM while load metrics stayed flat
    CyberAgent2026
  3. IL-0465 IONOS Container Registry image pushes and pulls failed with 504 Gateway Timeout
    IONOS Cloud2026
  4. IL-0100 PostHog's feature flags pods were packed onto Kubernetes nodes that were too small for their CPU requests, and CPU saturation above 90% caused three outages in ten days through Redis overload, connection pool exhaustion and slow queries
    PostHog2025
  5. IL-0413 LLM inference engines timed out or ran out of resources under load in about 60% of 156 severe incidents at Microsoft
    Microsoft2025
  6. IL-0082 Losing one CoreDNS pod during a planned EKS node reroll overloaded the remaining CoreDNS pods, causing DNS timeouts and errors across multiple services at RebelMouse
    RebelMouse2025
  7. IL-0204 An etcd memory spike overloaded the control plane of a Render Frankfurt cluster, and DNS then failed because CoreDNS ran on the rebooted control plane nodes and could not start without the API server
    Render2024
  8. IL-0232 Calico pods in the codfw WikiKube cluster hit their resource limits and crash-looped, taking nodes out one by one
    Wikimedia Foundation2024
  9. IL-0202 A burst of queries and database writes exhausted connection pools and memory on Honeycomb's ingest hosts, and Kubernetes crash-loop back-off kept failed hosts offline so ingest capacity stayed too low to recover
    Honeycomb2023
  10. IL-0433 Shifting API traffic from EC2 to EKS on Fargate overloaded two CoreDNS pods and caused mass name-resolution errors
    MonotaRO2023
  11. IL-0500 UToronto JupyterHub logins and server starts returned 500 errors when the hub's sqlite database disk filled up
    2i2c2022
  12. IL-0140 The GKE API in us-central1 returned errors and high latency for 3 hours 19 minutes after an unexpected rise in backend traffic that client retries made worse
    Google Cloud2022
  13. IL-0206 Consul agents in GitLab.com's GKE pods were repeatedly OOM-killed, so the Rails pods lost database replica discovery and sent every query to the primary
    GitLab2022
  14. IL-0013 The conntrack table filled up on downsized GKE nodes and a high-traffic aggregation proxy saw climbing connection resets
    loveholidays2020
  15. IL-0002 CI builder pods could not get AWS IAM credentials because kubelet fell minutes behind its API rate limit
    Zalando2019
  16. IL-0064 CPU-heavy pods packed onto one Google Cloud node drove it to kernel panics, and the crash moved from node to node until the site was down
    Moonlight2019
  17. IL-0075 Kubernetes API servers pegged on CPU when the cluster grew to about 290 nodes, traced to Datadog agents polling the API
    Civis Analytics2019
  18. IL-0001 Cluster-wide DNS outage after CoreDNS pods were OOM-killed again and again under a burst of DNS queries
    Zalando2019
  19. IL-0031 Kubernetes API server OOM-killed, leaving the Skipper ingress without routes; the talk points to a misconfigured CronJob manifest
    Zalando2018
  20. IL-0518 gitlab.freedesktop.org on GKE ran short of volume space and a planned 30-minute storage upgrade became a 4-hour outage
    freedesktop.org2018
  21. IL-0468 New JupyterHub student pods stuck Pending on MaxVolumeCount after a memory limit cut with node size unchanged
    UC Berkeley2017

Cloud provider outage5 cases

Component
Database3Cloud load balancer2AKS control plane1CDN and edge network1Cluster autoscaler1GKE control plane1Horizontal pod autoscaler1Ingress controller1Node root disk1Persistent volumes and stateful sets1Web application firewall rules1
Contributing factor
Overlapping failures2Single point of failure2Unverified assumption1Excessive blast radius1Unpatched known bug1Harmful manual action1No headroom1Health check tied to a dependency1Retry storm1
Organisation
ANDPAD1Grafana Labs1Microsoft Azure1OpenAI1Twingate1
  1. IL-0438 Builder Work became almost entirely unreachable with 504 errors when the Amazon CloudFront VPC Origins feature failed
    ANDPAD2026
  2. IL-0542 Twingate authentication and authorization requests failed at higher rates after traffic moved onto a smaller GKE cluster
    Twingate2025
  3. IL-0119 ChatGPT web service pods crash-looped on failing health checks after a Cosmos DB failure, leaving too few healthy pods to serve the web layer
    OpenAI2025
  4. IL-0145 A power sag and chiller failure in one Australia East availability zone took down the AKS control plane's compute and its non-zone-redundant SQL Database operation queue, blocking AKS create, update and delete operations in Australia East and Australia Southeast
    Microsoft Azure2023
  5. IL-0193 A GCP persistent disk degradation took down a Cassandra StatefulSet whose OrderedReady policy blocked recovery, and Metrictank could not reconnect to the recreated pods, causing a 23-hour Graphite query outage
    Grafana Labs2019

Breaking change in an upgrade4 cases

Component
Admission webhook1Calico1etcd1Model inference server1Ingress controller1Istio1Kubernetes API server1Linux kernel1Web application firewall rules1
Contributing factor
Unrepresentative staging2Untested backup1Configuration not in code1Ignored early signal1Monitoring blind spot1Single point of failure1
Organisation
GitHub1Reddit1UK Ministry of Justice1Wikimedia Foundation1
  1. IL-0092 Upgrading ingress-nginx from 1.12.0 to 1.14.3 brought a newer ModSecurity and OWASP Core Rule Set whose false positives blocked HMPPS Auth, so users could not sign in to their applications
    UK Ministry of Justice2026
  2. IL-0236 After an Istio 1.15 to 1.24 upgrade, half of Wikimedia's ML model servers returned 5XX for about a day
    Wikimedia Foundation2026
  3. 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
  4. IL-0060 Kubernetes 1.24 upgrade removed the master node label that Calico route reflectors selected on, dropping all pod routes and taking Reddit down for 314 minutes
    Reddit2023

Faulty deployment2 cases

Component
In-memory cache1CI system1Cloud load balancer1ConfigMaps and Secrets1Database1Helm1Ingress controller1Pod termination1
Contributing factor
Unverified assumption2Signal buried in noise1Unreviewed defaults1Monitoring blind spot1Dependence on a warm cache1
Organisation
Wikimedia Foundation1Yonghyun Kim1
  1. IL-0188 Rolling updates on EKS returned 502 errors for about 30 seconds because Kubernetes deleted old pods as soon as new pods passed readiness, before the ALB had marked the new pod targets healthy
    Yonghyun Kim2025
  2. IL-0324 Three MediaWiki deployments lost Memcached after a PHP 8.1 rollout and overloaded the External Storage database cluster
    Wikimedia Foundation2025

Data loss or corruption1 case

Component
Container registry and its credentials
Contributing factor
Cache-masked failure
Organisation
Harness
  1. IL-0474 Harness Feature Flags auth returned 502s when rescheduled pods could not get an image deleted from Artifact Registry
    Harness2025

Software defect9 cases

Component
kubelet3Cloud load balancer2etcd2Ingress controller2Admission webhook1Container CPU limit1Database1Authoritative DNS servers and records1Liveness and readiness probes1Horizontal pod autoscaler1Kubernetes API server1Linkerd1Linux kernel1Node pool1Serverless function platform1
Contributing factor
Monitoring blind spot3Automation amplification2Change with a delayed effect2Unpatched known bug2Unknown limit2Excessive blast radius1Unreviewed defaults1Ignored early signal1Harmful manual action1No configuration tests1No runbook1No safeguard on destructive change1No headroom1Overlapping failures1Retry storm1Ineffective rollback1Single point of failure1
Organisation
Amazon Web Services2Airbnb1AirMap1DFDS1Grafana Labs1HubSpot1Monzo1Omio1
  1. IL-0150 A latent race condition in DynamoDB's DNS automation left an empty DNS record for dynamodb.us-east-1.amazonaws.com, and the DynamoDB and EC2 launch failures that followed caused EKS, ECS and Fargate container launch failures and cluster scaling delays in us-east-1
    Amazon Web Services2025
  2. IL-0495 HubSpot's internal load balancers on Kubernetes were falsely marked unhealthy and the rest collapsed under the traffic
    HubSpot2024
  3. IL-0151 A latent defect in the AWS Lambda Frontend, set off when one us-east-1 cell scaled past a size never reached before, raised errors for Lambda and for services that depend on it, including new EKS cluster provisioning
    Amazon Web Services2023
  4. 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
  5. IL-0032 Mutating admission controller generated broken JSON patches, silently blocking deploys for a week until a production service ran down to two pods
    Airbnb2020
  6. IL-0190 Cortex distributors kept a stuck connection to a dead etcd leader after a Kubernetes upgrade terminated its node, failing writes to Hosted Prometheus for 12 minutes
    Grafana Labs2020
  7. IL-0012 CPU limits and an unpatched kernel CFS quota bug throttled multi-threaded services into stalls, failed health checks and timeouts
    Omio2020
  8. IL-0074 All AirMap platform services down as worker nodes went NotReady and pods crash-looped on network and DNS failures
    AirMap2018
  9. IL-0003 linkerd lost Kubernetes service discovery after an etcd reconfiguration, and restarting every linkerd instance turned failed payments into a full platform outage
    Monzo2017

Certificate or credential expiry1 case

Component
Cluster autoscalerManaged Kubernetes control plane and provider API
Contributing factor
Change with a delayed effect
Organisation
Linode
  1. IL-0156 Revoking old certificates after a rotation left a certificate key mismatch between API endpoints and the cluster controller, and LKE cluster management and autoscaling in Atlanta returned 5xx errors
    Linode2025

DNS or network fault3 cases

Component
conntrack table2CoreDNS2kube-proxy2Cloud load balancer1Client-side DNS resolver and cache1Horizontal pod autoscaler1Ingress controller1Pod termination1Telemetry agent1
Contributing factor
Unreviewed defaults2Ignored early signal2Unverified assumption1Automation amplification1Unknown limit1No caching1
Organisation
Adevinta1Lotte E-commerce1Preply1
  1. IL-0083 Intermittent 5xx errors in a multi-tenant Kubernetes cluster came from internal DNS: the node-local dnsmasq hit its 150 concurrent query limit, did not cache cluster.local answers, and ndots search lookups flooded CoreDNS
    Adevinta2023
  2. IL-0178 On EKS, HPA scale-in returned 502 errors because containers stopped before their pod IPs left the Service endpoints, and after blue/green switches conntrack kept sending established connections to deleted pods behind an instance-mode ALB
    Lotte E-commerce2022
  3. IL-0049 Partial DNS outage after CoreDNS scaled down and kube-proxy failed to delete stale conntrack entries
    Preply2020

Operator error2 cases

Component
Database1Ingress controller1Model hub1
Contributing factor
No safeguard on destructive change2No headroom1Overlapping failures1Deferred upgrades1
Organisation
GitLab1OpenAI1
  1. IL-0207 A routine task run from an engineer's local environment switched to production and deleted GitLab.com's Consul release, so Patroni lost Consul and GitLab.com returned 5xx errors to all traffic
    GitLab2022
  2. IL-0115 One of OpenAI's three production AKS clusters went offline through a human error, and rebuilding it took 10½ hours because an AKS Kubernetes upgrade broke the ingress and AKS cannot be downgraded
    OpenAI2022