Cases16 cases

6 to 10 of 16

1. IL-0152 An incorrect configuration applied during maintenance made an internal infrastructure cluster automatically delete the control planes of 200 DOKS clusters in FRA1

   DigitalOcean2024

   Symptoms

   At 13:02 UTC on 2024-01-23 DigitalOcean posted that, as of 12:18 UTC, its engineers were investigating an issue with Kubernetes clusters in the FRA1 region and that users might see errors when communicating with their clusters. The control planes of the affected DOKS (DigitalOcean Kubernetes) clusters had become inaccessible.

   Resources deletedControl plane unresponsive

   Trigger

   An incorrect configuration was applied to an internal infrastructure cluster in FRA1 at 12:21 UTC during a maintenance operation.

   Root cause

   Configuration change

   Component

   etcdKubernetes API server

   Contributing factor

   Automation amplificationNo safeguard on destructive changeExcessive blast radius

   Detection

   Engineers were investigating errors with Kubernetes clusters in FRA1 as of 12:18 UTC and identified the incorrect configuration as the cause at 12:36.

   Remediation

   • restored each affected cluster's etcd from its latest twice-daily backup
   • restored the stateless control plane components after etcd
   • patched the recovery mechanism after unexpected problems during recovery
   • found and fixed an additional small bug during recovery
   • contacted affected customers directly with further instructions, since some might need to reconfigure Kubernetes resources

   Action items

   • Prevent automatic deletion of infrastructure cluster resources under any circumstances in the production environment

   Lessons

   When managed control planes run as resources in another cluster, one configuration mistake in that cluster can delete hundreds of control planes at once through ordinary automation. The etcd backups limited the damage, but their twice-daily schedule set the worst case at 12 hours of lost control plane state, and the recovery tooling itself needed patching during the incident.

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2. IL-0473 Jenkins infrastructure went fully down after a pod IP range fix deleted every AKS node pool and could not recreate them

   Jenkins project2023

   Symptoms

   On 7 July 2023 from 11:05 to 15:25 UTC many public Jenkins infrastructure services were completely down, including get.jenkins.io, plugins.jenkins.io, accounts.jenkins.io, javadoc.jenkins.io and incrementals.jenkins.io, while ci.jenkins.io, issues.jenkins.io, repo.jenkins-ci.org and www.jenkins.io were partly or completely disrupted.

   Network unreachableResources deletedCluster or node provisioning stallService outage

   Trigger

   After the upgrade to Kubernetes 1.25 changed the range of the pods' originating IP and LDAP access was blocked, a fix (Azure PR 431) deployed at 10:55 UTC to set a proper set of pod IP ranges removed all node pools of the cluster.

   Root cause

   Configuration change

   Component

   Node poolCNI pluginCloud load balancer

   Contributing factor

   Unverified assumptionNo staged rolloutNo safeguard on destructive change

   Detection

   After the upgrade, at 10:30 UTC, the team noticed that services inside the cluster, such as accounts.jenkins.io, could not reach the LDAP service.

   Remediation

   • Created the cluster again from scratch with a fixed network setup
   • Set a custom pod CIDR in a range separate from the virtual network
   • Moved the services and their DNS records to new public IPs
   • Pushed a pull request that recorded the manual rebuild, including the IP setup, in code

   Action items

   • Protect the public IPs from deletion with a Management Lock
   • Keep the public IPs in a separate resource group and point the Kubernetes-managed load balancers to it with the service.beta.kubernetes.io/azure-load-balancer-resource-group annotation
   • Improve network diagrams and documentation so possible overlaps are visible when preparing operations
   • Avoid changing the configuration of all AKS node pools at once

   Lessons

   The team said that changing one node pool at a time would have shown the problem after the first pool and avoided a full outage, and that the public IPs should change as little as possible because users behind corporate firewalls with allow-lists depend on them. The team also noted that it could rebuild, in under 4 hours, the cluster that hosts almost all public services.

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3. IL-0068 Anonymous access to the Kubernetes API server used to plant a ClusterRoleBinding backdoor and a cryptominer DaemonSet

   Aqua Security2023

   Symptoms

   Aqua's research team Nautilus recorded the attack on one of its Kubernetes honeypots. What appeared in the cluster was a DaemonSet running the image kuberntesio/kube-controller:1.0.1 from Docker Hub on every node, using the nodes' CPU to mine Monero.

   Unauthorised access or a foreign workloadResources deleted

   Trigger

   An API server misconfigured to accept unauthenticated requests from anonymous users with privileges.

   Root cause

   Configuration change

   Component

   Kubernetes API serverRBAC and service accountsContainer registry and its credentials

   Contributing factor

   Monitoring blind spot

   Detection

   Aqua recorded the attacker's API requests on its honeypot; planted AWS access keys raised a beacon when the attacker tried to use them.

   Lessons

   Fixing an exposed API server is not enough once an attacker has been in: a ClusterRoleBinding to an attacker-created ServiceAccount keeps working after anonymous access is closed. Attackers name these objects and images after real Kubernetes components so they blend into the API audit logs and pass for legitimate deployments. Aqua recommends scanning clusters for vulnerabilities, exposed secrets and misconfigurations with a tool such as Trivy.

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4. IL-0109 A retried node rollover on a DFDS EKS cluster set the Auto Scaling group back to 15 instances, and the default termination policy removed every healthy worker node, leaving the cluster with no nodes

   DFDS2023sev1

   Symptoms

   At 09:33 UTC on 14 February 2023 end users told the platform team that Kubernetes logs were not arriving in CloudWatch as expected. The investigation went through fluentd and found that the nodes were running containerd as their container runtime instead of docker-shim. A scheduled node rollover the day before, at 07:30 UTC on 13 February, had set containerd as the default runtime by accident.

   Service outageResources deletedMonitoring outage

   Trigger

   A scheduled node rollover had accidentally made containerd the default container runtime, which stopped log shipping to CloudWatch; the unscheduled rollover to revert it timed out, and the pipeline run that followed reduced the Auto Scaling group from 30 to 15 instances.

   Root cause

   Configuration change

   Component

   Container runtimeNode launch templateNode poolTerraformTelemetry agent

   Contributing factor

   Automation amplificationUnreviewed defaultsUnrepresentative stagingNo configuration testsNo runbookHarmful manual action

   Detection

   End users reported the missing CloudWatch logs that started the work. The postmortem lists 2 minutes as the time to detection of the node failure.

   Remediation

   • ran the node rollover script to add new nodes, which failed on a timeout from Docker Hub
   • ran the node rollover script a second time, which added new nodes that the load balancer marked healthy at 11:01 UTC

   Action items

   • Document the rollover process, especially what can be done when it goes wrong
   • Investigate options for improving the rollover process
   • Add fluentd log collection to the QA test suite so logs are covered end to end
   • Add alarms for fluentd when too little or no log data is sent
   • Implement a staging environment
   • Implement guards against selecting an invalid container runtime

   Lessons

   When a change goes wrong, rolling back to a known working configuration is safer than rushing a fix, which can make the damage worse. Launching new worker nodes depends on the cloud-init script not failing in any way. The QA configuration differed from production, there was no staging environment, the QA tests did not cover fluentd log collection, and the rollover process had no documentation for when it fails.

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5. 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

   Symptoms

   GitLab's monitoring and alerting fired at once. One of the alerts reported a Patroni failover, and users of GitLab.com received 5XX errors; the CDN counted about 13 million requests answered with 503 during the outage.

   Service outageHigh error rateResources deleted

   Trigger

   An engineer ran a routine task with GitLab's tools in a local development environment; during a local deploy or rollback operation the tool's context changed from local development to production, and the change was applied to production.

   Root cause

   Operator error

   Component

   Database

   Contributing factor

   No safeguard on destructive change

   Detection

   GitLab's monitoring and alerting fired immediately; one of the alerts reported a Patroni failover.

   Remediation

   • re-applied the Consul release to the production Kubernetes cluster, with manual steps because the tooling did not support the redeploy directly

   Action items

   • Improve the Kubernetes deployment process to reduce the risk of running harmful deployment operations against production from local environments (https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16875)
   • Integrate Teleport with the Kubernetes clusters, which could give SREs a read-only role by default (https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16221)

   Lessons

   A tool that can switch its target from a local environment to production during a deploy or rollback turns routine local work into a production change. GitLab plans to improve its Kubernetes deployment process so that harmful deployment operations are less likely to be run against production from local environments, and to integrate Teleport with its clusters, which could give SREs a read-only role by default. Detection and diagnosis were fast because the alerts led straight from Patroni to its dependency, Consul. Bringing the deleted release back needed manual work, because the tooling did not make the redeploy straightforward, but it was still done relatively quickly.

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