Cases8 cases

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1. IL-0192 A Crossplane composition merge-policy change for a TLS policy update switched Kubernetes Services from LoadBalancer to ClusterIP and deleted the load balancers behind about 25% of Grafana Cloud services

   Grafana Labs2025

   Symptoms

   At 08:41 UTC on 18 February 2025, several Grafana Labs application teams noticed that some of their endpoints were no longer available. The investigation quickly found that the load balancers for those endpoints were gone.

   Service outageResources deleted

   Trigger

   A change to the merge policy of a Crossplane composition, made so that the default TLS policy of the load balancers could be overridden, was applied to development, staging and production at the same time.

   Root cause

   Configuration change

   Component

   Configuration templatingCloud load balancer

   Contributing factor

   Unverified assumptionNo staged rolloutExcessive blast radiusNo safeguard on destructive change

   Detection

   Application teams noticed at 08:41 UTC that some of their endpoints were no longer available.

   Remediation

   • rolled back the Crossplane composition change
   • recreated the affected Kubernetes Services so that Kubernetes recreated their load balancers

   Action items

   • Add a CI check that blocks a deployment to more than one wave, so any exception to the dev, staging, canary, production order is caught
   • Give higher priority to a more sophisticated wave design that was already under discussion
   • Enable deletion protection on the load balancers, one layer below Crossplane
   • Enable deletion protection on other critical cloud provider resources
   • Develop the Crossplane Managed Resources exporter for change validation and visibility, now in beta testing within Platform engineering; simulated against the change that caused this outage, it shows a clear diff
   • Complete and test support for reconfiguring the TLS policy so application teams can deploy it

   Lessons

   A change that looked small and low-risk had a side effect that only a full end-to-end test through Crossplane and the cloud provider's load balancer controller would have shown; seeing the intended override work was not that test. Staged rollout and blast-radius limits that exist only as process can be skipped, so Grafana Labs moved to enforce waves in CI and to add deletion protection on the load balancers themselves, beneath the Crossplane layer.

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2. IL-0203 A routine Kubernetes cluster system update made the AWS Load Balancer Controller fail, so new pods were never registered with the ALB and Honeycomb's EU1 ingest and UI went down once the last old pods were replaced

   Honeycomb2024

   Symptoms

   Event ingestion and the Honeycomb UI in EU1 became unavailable at 22:00:10 UTC on April 9, 2024, and the status page reported that the EU1 instance was down. Both the ingestion service and the service behind the web UI stopped at roughly the same moment.

   Service outageStale endpoint routing

   Trigger

   A routine system update to the Kubernetes cluster, rolled out earlier on April 9, followed by a regular deployment that replaced pods one at a time.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerCloud load balancer

   Contributing factor

   Monitoring blind spotUnrepresentative stagingChange with a delayed effect

   Detection

   The first status post, saying the EU1 instance was down, went up at 15:08 PDT (22:08 UTC), about 8 minutes after the outage began. There was no alerting on the AWS Load Balancer Controller.

   Remediation

   • Restarted the AWS Load Balancer Controller
   • Rolled back the Kubernetes cluster system update

   Action items

   • Find the exact cause of the failure so the system update can be deployed safely
   • Add monitoring and alerting on the AWS Load Balancer Controller so on-call engineers learn of a failure quickly and can pause deployments

   Lessons

   A rolling deployment can look healthy while the component that wires new pods into the load balancer is broken; the failure only shows when the last old pod goes away. Honeycomb now treats the AWS Load Balancer Controller as a critical component that needs its own alerting, so deployments can be paused before they remove the last pods that still receive traffic. Extensive testing in development and staging did not reveal the bad interaction.

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3. 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

   Symptoms

   At 08:00 UTC on 2021-09-06 every service in DFDS's Kubernetes cluster answered with 404. Investigation started five minutes later.

   Service outageHigh error rateProbe failures

   Trigger

   The automated Kubernetes node rollover on 2021-09-06 restarted all the Traefik v2 pods, five days after a malformed IngressRoute manifest had been applied.

   Root cause

   Software defect

   Component

   Ingress controllerCloud load balancer

   Contributing factor

   Change with a delayed effectNo configuration testsExcessive blast radius

   Detection

   All services returned 404 from 08:00 UTC and root cause investigation started at 08:05. Time to detection was 5 minutes.

   Remediation

   • changed the ALB health check path, which made the targets healthy but did not stop the 404s
   • rolled back by hand to Traefik v1 as the main ingress controller
   • deleted the malformed IngressRoute by hand and confirmed the Traefik v2 bug
   • applied the changes upstream

   Action items

   • Upgrade Traefik to v2.5, where the bug is fixed, and verify that it removes the bug
   • Change the Traefik v2 health check path to something more robust
   • Set up an external liveness probe on the ingress controller
   • Consider workload segmentation to limit the blast zone
   • Look into monitoring the Traefik v2 API for rapid changes
   • Look into smoke testing during and after node rollover

   Lessons

   A malformed IngressRoute did nothing visible for five days and then took down all ingress when every Traefik v2 pod had restarted during a node rollover. Because Traefik v2 failed gracefully, the first signals pointed at the ALB health checks instead of at Traefik. On incident handling, the team concluded that appointing an incident manager could have helped, that the war room meeting should be recorded and a log book kept, that people not involved should only make suggestions in writing, and that a short first round of sharing thoughts and gut feelings is useful.

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4. 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

   Symptoms

   After the switch to Traefik v2, functional tests indicated that everything was fine, and this was reported on Slack at 08:44 UTC. The first sign of trouble came at 09:26 UTC, when a developer reported a high count of HTTP 307 redirects, especially on the Okta service. At 09:32 UTC the team learned that the online booking system was down.

   Service outage

   Trigger

   At 08:22 UTC the AWS load balancers were updated to send requests to the new Traefik v2 reverse proxy as part of the migration away from Traefik v1.

   Root cause

   Configuration change

   Component

   Ingress controllerCloud load balancer

   Contributing factor

   Missed in reviewMonitoring blind spot

   Detection

   A developer reported a high count of HTTP 307 redirects, in particular on the Okta service, at 09:26 UTC, 64 minutes after the change; six minutes later the team was told the online booking system was down. The functional tests run after the switch had not caught it.

   Remediation

   • Rolled back the switch to Traefik v2, putting rollback ahead of investigation because of how critical the booking system is

   Action items

   • Consider how critical announcements can be made more visible
   • Consider whether the ALBs used for testing should have been shared with the teams so they could test their own scenarios

   Lessons

   Cloud Engineering cannot test every application scenario on its own, even after testing its own applications for weeks. A header that changes value behind a new ingress controller, here x-forwarded-proto going from https to http, can break an authentication flow while basic functional tests still pass. DFDS asks whether diffing request headers before and after the migration would have shown the problem in advance.

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5. 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

   Symptoms

   At 08:29 UTC on 22 June 2021 alerts fired because all services in the Kubernetes cluster were returning 503. No inbound traffic was reaching the cluster. A customer reported the problem at 08:32.

   Service outageHigh error rate

   Trigger

   The pipeline replaced the AWS VPC CNI as part of a refactoring that moved EKS add-ons from kubectl to native Terraform management.

   Root cause

   Configuration change

   Component

   AWS VPC CNICloud load balancerTerraform

   Contributing factor

   Unverified assumptionNo configuration tests

   Detection

   Alerts fired at 08:29 UTC, eight minutes after the VPC CNI was replaced; a customer reported the issue at 08:32.

   Remediation

   • committed a fix that reverted the infrastructure-modules reference
   • re-triggered the pipeline after it failed on an AWS API timeout
   • let the pipeline reattach the target groups to the ALB

   Action items

   • Revert the ALB de-registration delay to the default of 300 seconds
   • Update the roll-over script to set the ALB de-registration delay to zero temporarily before a roll-over
   • Create an ingress test suite

   Lessons

   The change to the de-registration delay had been weighed mainly for performance. Critical pipeline runs should be watched while they run. Everyone should receive the alerts and react to them, and alert messages that were unclear should be reworded.

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