Cases9 cases

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1. IL-0103 During an EKS node AMI update, Istio sidecars crash-looped because hundreds of pods restarting at once overloaded the external certificate authority behind istiod

   Tetrate (unnamed U.S. federal customer)2025sev1

   Symptoms

   While the customer was updating the AMIs of its Amazon EKS nodes across more than 30 clusters running Istio, sidecar-injected workloads in one cluster failed to start and showed CrashLoopBackOff.

   Container crash loopProbe failures

   Trigger

   Updating the EKS node AMIs, which started hundreds of sidecar-injected pods at the same time.

   Root cause

   Dependency failure

   Component

   IstioAdmission webhookNode operating system image

   Contributing factor

   Unreviewed defaultsUnknown limit

   Detection

   Sidecar-injected workloads in the updated cluster failed to start and showed CrashLoopBackOff; the customer raised a Severity 1 ticket and a Tetrate engineer was reviewing logs within six minutes.

   Remediation

   • scaled istiod down temporarily from 40 replicas to 1 to slow Istio's internal processes and ease the load on the CA
   • deleted the CertificateSigningRequests stuck in the Approved, Failed state
   • restarted the pods gradually in a controlled order instead of all at once

   Lessons

   When a mesh hands certificate signing to an external CA, every pod start becomes a signing request to that CA, so a mass restart such as a node image rollout can overload it. Sidecars then abort under istiod's 10-second default CA timeout even though the CSRs are eventually signed. Restarting pods in controlled batches keeps the request rate within what the CA can handle. The author's point is that diagnosing such a failure means looking at the whole service mesh ecosystem, including its external dependencies, not only Istio.

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2. IL-0159 Docker Hub rate-limited Linode's IPv6 address space with 429 Too Many Requests, breaking image pulls for LKE and LKE-E clusters

   Linode2025

   Symptoms

   From about 21:38 UTC on 5 February 2025, image pulls from Docker Hub over IPv6 failed with 429 Too Many Requests errors across several Linode regions. Both unauthenticated and authenticated pull requests were refused.

   Image pull failures

   Trigger

   Docker Hub's abuse prevention measures started rate-limiting image pulls coming from Linode's IPv6 address space.

   Root cause

   Dependency failure

   Component

   Container registry and its credentialsVPC DNS resolver

   Contributing factor

   Unknown limit

   Detection

   The rate limiting began at about 21:38 UTC. The first status post, at 22:48 UTC, said Linode was aware of an issue with Docker Hub over IPv6 causing rate limiting and was investigating, and at 01:06 UTC on 6 February the status page said the issue had been identified as rate limiting of image pull requests to Docker Hub over IPv6.

   Remediation

   • changed the DNS resolvers to return an A record instead of an AAAA record so image pulls to Docker Hub used IPv4

   Action items

   • Find long-term solutions so that Docker Hub's abuse prevention measures do not affect Linode services

   Lessons

   A registry's abuse limit that groups IPv6 addresses by their first 64 bits can block a provider's whole address range at once, and authentication does not help. Answering DNS lookups with IPv4 addresses only was the quick way to move image pulls off the blocked range.

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3. IL-0489 Rejoining a failed node of Magic Pages' three-node MySQL cluster broke its metadata and took customer websites down

   Magic Pages2025

   Symptoms

   On 15 January 2025, from about 09:55 to 11:36 CET, a database outage at Magic Pages took down customer websites. It began when the founder tried to reconnect a failed third node to the high-availability MySQL cluster and the database server reported ambiguous errors about missing metadata information.

   Service outage

   Trigger

   One of the three nodes of the MySQL cluster went down, and reconnecting it failed with errors about missing metadata information.

   Root cause

   Dependency failure

   Component

   DatabasePersistent volumes and stateful sets

   Contributing factor

   Harmful manual actionSingle point of failureMonitoring blind spot

   Remediation

   • Restarted the storage server to fix PVC provisioning
   • Let the MySQL nodes restore and sync with each other for about 45 minutes to rebuild the cluster metadata
   • Cleaned up the corrupted cluster metadata
   • Redeployed MySQL Router

   Action items

   • Monitor the health of the storage system more closely
   • Improve the failover procedures for MySQL Router
   • Investigate and fix the status page so it shows reliable information

   Lessons

   The cluster survived the first node failure as designed and lost no data, but its metadata turned out to be a single point of failure. Better monitoring of PVC health could help prevent similar issues, the 45-minute recovery leaves room for improvement, and the status page has to detect failing customer sites reliably.

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4. IL-0021 GKE GPU nodes on Container-Optimized OS could not download NVIDIA drivers (403 Forbidden) and came up without working GPUs

   Google Cloud2024

   Symptoms

   From 08:00 US/Pacific on 12 March 2024, GKE GPU nodes running Container-Optimized OS (COS) that were newly created or recreated came up with GPU drivers that did not work, so workloads that used the GPUs could not run. GKE showed elevated errors.

   GPU unavailableNode NotReady

   Root cause

   Dependency failure

   Component

   GPU driverNode operating system imageNode pool

   Contributing factor

   Automation amplification

   Detection

   The report does not say how Google detected the issue. Affected users saw "Failed to download GPU driver installer, status: 403 Forbidden" on the GPU node when installing the driver.

   Remediation

   • Halted automatic node recreations, which attempt GPU driver downloads, until the issue was mitigated
   • Worked with the driver partner to resolve access to the driver download bucket

   Lessons

   The status page report states no lessons or follow-up actions.

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5. IL-0039 New Kubernetes worker nodes could not join any cluster because a package URL hardcoded in kops nodeup broke

   FREE NOW2019

   Symptoms

   At 16:00 CEST a developer reported in the #ask-platform Slack channel that a deployment to the Prelive cluster was failing, and a second report followed at 16:06.

   Pods PendingScale-up failure

   Trigger

   Roughly two to three days earlier, the CentOS repository mirror was restructured and container-selinux-2.68-1.el7.noarch.rpm moved, which made the static download URL hardcoded in kops nodeup invalid.

   Root cause

   Dependency failure

   Component

   Node operating system imageNode pool

   Contributing factor

   Monitoring blind spot

   Detection

   Developers asked for help in the #ask-platform Slack channel because their deployments were failing.

   Remediation

   • downloaded the package by hand on the Prelive nodes so their bootstrap could finish
   • changed the cluster AMI from Amazon Linux 2 to Debian and applied it to all clusters

   Action items

   • Create an alert that shows when nodes cannot join the cluster, possibly from information the cluster autoscaler already has
   • Document the external dependencies of node startup and look for ways to reduce them
   • Change the AMI back to Amazon Linux 2 Minimal once kops fixes the issue
   • Document node troubleshooting better: what happens during bootstrap and where the logs are

   Lessons

   Applying cluster changes through kops and Jenkins worked well, and troubleshooting quickly showed that the failing deployments came from missing cluster capacity. What went wrong was that nobody noticed, over a long period, that some autoscaling groups held more worker instances than Kubernetes had nodes. The team was lucky that no large number of production spot instances was terminated during the problem and that it was noticed during office hours.

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