Cases32 cases

2 to 6 of 32

1. IL-0098 After 2i2c moved from ingress-nginx to nginx-ingress, a hub's Ingress took priority over cert-manager's temporary Ingress for the same host, so new hubs could not get TLS certificates

   2i2c2026

   Symptoms

   An attempt to launch a new hub failed because its ingress could not obtain a new TLS certificate. The day before, the same engineer had recreated the support deployment on the 2i2c-aws-us cluster and seen its TLS certificate orders stuck pending.

   Misrouted requestsDeploys failing

   Trigger

   Creating new hub deployments that needed new TLS certificates on clusters recently migrated from ingress-nginx to nginx-ingress.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllercert-manager

   Contributing factor

   Change with a delayed effect

   Detection

   An attempt to launch a new hub failed; the engineer had seen certificate orders stuck pending on another cluster the day before and declared an incident.

   Remediation

   • annotated the Ingress objects that need TLS so that cert-manager could edit them in place to complete the ACME challenge

   Action items

   • Follow-up tracked in https://github.com/2i2c-org/infrastructure/issues/8016
   • Follow-up tracked in https://github.com/2i2c-org/infrastructure/issues/3278

   Lessons

   Swapping one ingress controller for another can change how Ingress objects that share a host are combined. cert-manager's temporary challenge Ingress depends on that behaviour, so the breakage shows up when a deployment needs a new certificate. 2i2c notes that it got lucky: it had already learned of this possible cause while testing on an internal cluster, and changing the cert-manager configuration was quick.

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2. 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

   Symptoms

   At 08:56 on 30 March 2026, about an hour and three quarters after the rollout of a new ingress-nginx to production began, the MoJ Cloud Platform team noticed messages in the #hmpps-auth-audit-registers Slack channel about ModSecurity unexpectedly blocking requests. Users in HMPPS also raised incidents with the MoJ service desk.

   High error rateService outage

   Trigger

   The Cloud Platform team began deploying ingress-nginx 1.14.3, on images maintained by Chainguard, to the three production ingresses at 07:11 on 30 March 2026.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerWeb application firewall rules

   Contributing factor

   Unrepresentative staging

   Detection

   At 08:56 the Cloud Platform team saw messages in the #hmpps-auth-audit-registers Slack channel showing ModSecurity blocking requests unexpectedly; HMPPS users also raised incidents with the MoJ service desk.

   Remediation

   • rolled the ingress-nginx deployment back to the previous version, from 09:14 to 09:43
   • HMPPS applied ModSecurity rule exclusions for the rules blocking traffic to HMPPS Auth
   • added a temporary global exclusion for the CRS rule triggered by the PostHog cookie
   • redeployed ingress-nginx 1.14.3 with both exclusions in place, completed at 14:00

   Action items

   • Rescope the PostHog cookie so it is no longer sent with requests to all *.justice.gov.uk services
   • Remove the temporary global exclusion once the PostHog cookie has expired from enough users' browsers
   • Remind service teams to run dev and test workloads through the non-production ingress controllers so future ModSecurity and CRS updates are tested
   • Run production and non-production workloads in separate clusters in Cloud Platform 3.0, so non-production workloads must use the non-production ingress

   Lessons

   An ingress controller upgrade that bundles a web application firewall also changes which requests are allowed, not only how they are routed. A beta or non-production ingress only catches false positives for traffic that actually passes through it, and teams that keep their test workloads on the production ingress miss them. A fix on the client side, such as rescoping a cookie, takes effect only when old cookies have expired in users' browsers, so the rule change has to wait for it or ship with an exclusion.

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3. IL-0405 An expired AWS Load Balancer Controller webhook certificate left no healthy targets and took BSEE SaaS down

   PortSwigger2026

   Symptoms

   From 10:00 UTC on 11 January 2026 every BSEE SaaS instance in PortSwigger's US and Canada regions was unavailable: customers could not open the Web UI or start scans. The platform team learned of it only when customers reported it through support at 09:52 UTC the next day.

   Service outageTLS certificate errors

   Trigger

   The upgrade of the AWS Load Balancer Controller from v1.14.1 to v1.16.0 on 28 November 2025 left an orphaned webhook TLS secret that cert-manager could not renew, and the certificate in it expired on 8 January 2026.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerAdmission webhookcert-managerHelmConfigMaps and SecretsCloud load balancer

   Contributing factor

   Change with a delayed effectMonitoring blind spot

   Detection

   Customers reported the outage through support at 09:52 UTC on 12 January 2026, almost 24 hours after impact began, and the platform team began investigating at 10:00 UTC.

   Remediation

   • Deleted the orphaned aws-load-balancer-tls secrets in the US and Canada clusters
   • Redeployed the AWS Load Balancer Controller configuration with Helm
   • Verified that new certificates were generated and the webhooks worked again

   Action items

   • Audit all clusters for orphaned secrets that have no owning Certificate resource and resolve them
   • Add high-level application access alerting for each SaaS cluster from an external probe

   View case
4. 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

   Symptoms

   Every rolling update of the team's microservices on Amazon EKS, behind an Application Load Balancer, was followed by intermittent 502 and 503 errors for users. A Slack message at 3 a.m. read "배포는 성공했는데, 서비스는 죽었다" (the deployment succeeded, but the service died). Every pod was Ready and Datadog was green while users saw errors.

   High error rateService outage

   Trigger

   A rolling update of a Deployment served through an ALB that registers pod IPs as targets, with no pod readiness gates.

   Root cause

   Faulty deployment

   Component

   Cloud load balancerIngress controllerPod termination

   Contributing factor

   Unverified assumptionUnreviewed defaultsMonitoring blind spot

   Detection

   A Slack message at 3 a.m. reported that the deployment had succeeded but the service was down; Datadog dashboards were green at the time.

   Remediation

   • labelled the namespace with elbv2.k8s.aws/pod-readiness-gate-inject=enabled so the AWS Load Balancer Controller injects pod readiness gates and Kubernetes waits for the ALB target to be healthy before deleting old pods

   Lessons

   A pod being Ready in Kubernetes does not mean the load balancer will send it traffic. Without a readiness gate, a rolling update can delete the old pods while the ALB still considers the new targets unhealthy, and dashboards that track pod status stay green during the errors. Making pods wait longer on shutdown reduced the errors but did not fix the start-up gap and made every deployment much slower; the readiness gate ties the pod's Ready state to the ALB's view of the target.

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5. IL-0095 An engineer deleted the prod namespace of the LEAP JupyterHub while believing the kubeconfig pointed at a new cluster, and the hub was down for about an hour

   2i2c2025

   Symptoms

   At 5:00 PM BST on 12 August 2025 a 2i2c engineer declared an incident. While deploying a new cluster called temple and running into NFS issues, the engineer had deleted the prod namespace; the deletion hung, and listing the pods showed many users from a different cluster. The engineer's first message suggested that the kubeconfig had somehow been mutated or corrupted and that some other cluster was being torn down.

   Resources deletedService outage

   Trigger

   While working around a bug in the NFS deployment process for a new hub, an engineer ran a delete of the prod namespace with the kubeconfig context pointing at the LEAP cluster.

   Root cause

   Operator error

   Component

   Persistent volumes and stateful setsJobs and CronJobsIngress controllerTerraform

   Contributing factor

   No safeguard on destructive changeNo runbook

   Detection

   The engineer who ran the deletion noticed when it hung and the pod list showed users of another cluster, and declared the incident at 5:00 PM BST, before the uptime check on leap.2i2c.cloud failed at 5:32 PM.

   Remediation

   • deleted the single remaining user pod in prod so the namespace deletion completed
   • killed the nfs-share-creator job that was blocking the deployment
   • redeployed the prod hub with the updated NFS server IP address
   • deleted the prod ingress during the deployment so that users could not start servers mid-deployment

   Action items

   • Write an incident report
   • Write a short incident response document for the case "I deleted prod, what next?"
   • Upgrade jupyterhub-home-nfs and remove the nfs-share-creator job
   • Add opt-in hardening against nested kubeconfig contexts to the deployer system
   • Change the engineer's shell configuration to show distinct kubeconfig contexts more clearly

   Lessons

   Provisioning persistent storage outside Kubernetes with Terraform meant a deleted namespace cost an hour of downtime and no data. The engineer had no visible cue for which kubeconfig context was active, which turned a workaround on a new cluster into a deletion on a production one. The engineer knew the fix but did not feel confident redeploying without first confirming with the tech lead, in another time zone, that there was no risk of losing persistent data, and reaching the tech lead took time.

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