Cases24 cases

1 to 5 of 24

1. IL-0471 GitHub Actions runs failed or sat queued for 9 hours after a routine deployment's pod replacement saturated capacity

   GitHub2026

   Symptoms

   From 15:05 UTC on 6 August 2026 GitHub Actions workflow runs failed to start, failed partway through or stayed queued for a long time, on both GitHub-hosted and self-hosted runners. Some requests to the Actions REST API returned errors, and some customers saw unexpected rate limiting in their workflows.

   High error rateHigh latency

   Trigger

   A routine deployment to an internal Actions service that processes events and generates Actions jobs replaced pods, and the remaining capacity became saturated.

   Root cause

   Capacity exhaustion

   Component

   CI system

   Contributing factor

   No headroomExcessive blast radiusHarmful manual action

   Remediation

   • Expanded capacity of the affected services
   • Throttled incoming webhook-triggered work
   • Increased processing capacity for the backlog of affected events
   • Deployed changes that stopped runners from repeatedly trying to acquire invalid jobs
   • Deployed a fix for self-hosted runners that were not picking up jobs and enabled it incrementally
   • Paused migrations with GitHub Enterprise Importer
   • Restored webhook-triggered Actions workflows to full throughput
   • Rolled back the mitigation that left some ARC runners offline, and recovered those runners by hand
   • Shared CLI and UI steps for customers to clear jobs that could not be retried or canceled

   Action items

   • Improve deployment and capacity safeguards for the affected services
   • Strengthen monitoring for the conditions that preceded the incident
   • Improve the resiliency and recovery of queued work and runner assignment
   • Add automatic recovery for self-hosted runners in upcoming Runner and ARC releases
   • Reduce the risk of cascading failures and speed up recovery during large Actions disruptions

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2. IL-0058 Argo CD deleted namespaces shared by several applications, leaving about 97 applications stuck Missing and OutOfSync

   Argo CD users2026

   Symptoms

   After a rolling restart of the Argo CD application-controller, namespaces that several applications shared went into the Terminating state. About 97 applications were then stuck in a Missing/OutOfSync deadlock.

   Resources deleted

   Trigger

   A manual bulk sync with force: true from the Argo CD UI, run during the window after an application-controller restart, on an application whose manifests declared a namespace whose app.kubernetes.io/instance label pointed to a different application.

   Root cause

   Software defect

   Component

   Argo CD

   Contributing factor

   No safeguard on destructive changeUnverified assumptionHarmful manual action

   Action items

   • Refile the problem as #29739: a manual force sync hard-replaces shared cluster-scoped resources through a tracking-ID conflict, ignoring Prune=false

   Lessons

   The sync option Prune=false only protects the prune path; it does not stop a force sync from deleting and recreating a resource. When two Argo CD applications declare the same namespace or other cluster-scoped resource, force-syncing the application that does not own the tracking label can delete it at any time.

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3. IL-0470 Buildkite notifications were delayed after Prometheus storage filled and EKS notification workers could not autoscale

   Buildkite2026

   Symptoms

   From 20:01 UTC on 28 May 2026, Buildkite build and job notifications (GitHub commit status, email, Slack and webhook notifications) reached a subset of customers late. Internal queue latency monitoring showed the delay as queues grew while notification-processing workers stayed underprovisioned.

   High latencyAutoscaler misbehaviour

   Trigger

   The Prometheus service used by Buildkite's EKS autoscaling path ran out of storage, so some EKS-based notification workers could not autoscale while their queues were growing.

   Root cause

   Capacity exhaustion

   Component

   Prometheus

   Contributing factor

   No alert on limitPartial rolloutIneffective rollbackUnverified assumptionHarmful manual action

   Detection

   Internal queue latency monitoring detected the rising notification delivery latency.

   Remediation

   • Moved the affected notification-processing workloads from EKS back to the ECS-based infrastructure
   • Adjusted scaling configuration and worker counts by hand
   • Completed the rollback and scaled the remaining affected ECS services
   • Increased Prometheus storage capacity and recorded the change in infrastructure as code

   Action items

   • Alert before Prometheus storage exhaustion can affect autoscaling
   • Fix GitHub notification retry behaviour for a class of errors that could cause repeated retries
   • Make the EKS-to-ECS rollback verify destination capacity, autoscaling configuration and traffic movement
   • Review the CPU, memory and storage allocations of EKS control-plane dependencies such as KEDA and Karpenter
   • Move customer-critical workloads to EKS more gradually, with clearer settling periods
   • Improve customer-level monitoring of notification delivery latency to detect customer-impacting regressions earlier
   • Review which notification types sit on customers' scheduling or CI hot path and need tighter latency, separate queueing or specific alerting
   • Update the status page earlier when notification latency is likely to affect customer workflows
   • Describe the customer-visible impact in status page updates, not only the affected internal service
   • Improve internal escalation for customers who report critical CI impact

   Lessons

   Buildkite said recovery took longer than expected because the rollback path from EKS to ECS did not fully handle this failure, and that its public status page did not show the customer-visible impact as quickly or clearly as it should have, since notification latency affects customers differently depending on how their CI and deployment workflows use notifications.

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4. IL-0006 VPC subnets ran out of IP addresses because the AWS VPC CNI kept IPs on full nodes, and WARM_IP_TARGET changes then blocked pod starts after every pod deletion

   Neon2025

   Symptoms

   On 16 May 2025, in Neon's Kubernetes cluster in AWS us-east-1, new compute pods were scheduled but could not start and failed with IP allocation errors. Each Neon compute is a Postgres database running in a lightweight virtual machine in its own pod, so without new pods, idle customer databases could not be woken up.

   IP address exhaustionPods Pending

   Trigger

   On 16 May the Neon control plane's periodic job that terminates idle computes started failing. Compute creations continued, and the number of active computes rose from about 5k to about 8.1k within minutes. On 19 May, a follow-up change that set WARM_IP_TARGET back to 1 started the second round of failures.

   Root cause

   Capacity exhaustion

   Component

   AWS VPC CNIVPC subnet or pod address rangeCluster autoscaler

   Contributing factor

   Unreviewed defaultsNo capacity planningUnverified assumptionHarmful manual actionIneffective rollbackRetry storm

   Detection

   As cluster-autoscaler added nodes, the team saw IP allocation errors on new pods that were scheduled but could not start. The rate of successful pod starts and VPC subnet metrics were then used to follow the problem.

   Remediation

   • Set WARM_IP_TARGET=1 to release IPs held by nodes without free CPU or memory
   • Fixed the control plane's periodic job so idle computes were terminated again
   • Restarted the aws-node DaemonSet several times, each with a temporary improvement
   • Set WARM_IP_TARGET=0, MINIMUM_IP_TARGET=0 and WARM_ENI_TARGET=0, which let nodes allocate enough IPs and stabilised the cluster
   • On 19 May, set WARM_IP_TARGET back to 0 after setting it to 1 failed again
   • Enlarged the pool of pre-created warm compute pods to absorb failed pod starts

   Action items

   • Open a pull request to AWS CNI to improve how ipamd releases IPs in this situation
   • Follow up with AWS Support about the roughly 100 subnet IPs that were never allocated, for reasons Neon could not explain
   • Change the architecture to support horizontal scaling

   Lessons

   With default settings AWS CNI can keep many IPs on nodes that cannot use them, so the share of subnet IPs assigned to pods does not tell how close the subnet is to running out. WARM_IP_TARGET and WARM_ENI_TARGET follow different logic, a warm IP target of zero switches to the ENI logic, and IPs in cooldown count toward the target, which behaves badly under high pod churn. Changing these settings during an incident without knowing that logic prolonged the outage, and reverting a setting did not bring back the earlier healthy state.

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5. IL-0542 Twingate authentication and authorization requests failed at higher rates after traffic moved onto a smaller GKE cluster

   Twingate2025

   Symptoms

   On 21 March 2025, between 21:10 and 21:41 UTC, part of the authentication and authorization requests to Twingate services failed with elevated error rates.

   High error rate

   Trigger

   Twingate saw anomalies in one of its GKE clusters and scaled down the deployments in that cluster to protect the rest of the system, which moved its traffic to the other clusters.

   Root cause

   Cloud provider outage

   Component

   Cloud load balancerGKE control planeHorizontal pod autoscalerCluster autoscaler

   Contributing factor

   Retry stormNo headroomOverlapping failuresHarmful manual action

   Detection

   Twingate observed anomalies in one of its GKE clusters at the start of the incident.

   Remediation

   • Reintroduced capacity in the cluster that had been scaled down, so traffic was rebalanced across regions

   Action items

   • Keep working with the cloud provider to find the cause of the unexpected timeouts and of the cluster update's impact
   • Run deployments in all regions with the same number of replicas in the HPA configuration
   • Raise the maximum node counts of the cluster node autoscalers to leave more room to scale up
   • Configure the HPA to scale up faster

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