Cases2 cases

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1. IL-0084 Packet drops on a bare metal provider's vSwitch forced Namespace to rebuild its fra3 region and left global capacity short, and the next day slow NVMe writes on a control plane node drove the Kubernetes API server to very high CPU

   Namespace2024

   Symptoms

   From 17 October 2024, packets through the vSwitch that joined Namespace's bare metal machines at one provider in the fra3 region were dropped at random. Retries in TCP, QUIC and the Namespace control plane hid most of it, but the SLO error budget for latency targets on key interactions began to burn.

   Intermittent connection failuresHigh latencyControl plane lagService outage

   Trigger

   Random packet drops on the bare metal provider's vSwitch from 17 October 2024; for the second outage, a rate of Kubernetes changes that the slow NVMe on one control plane node could no longer keep up with.

   Root cause

   Cloud provider outage

   Component

   Kubernetes API server

   Contributing factor

   No capacity planningNo headroomOverlapping failures

   Detection

   SLO-based monitoring of latency targets showed the error budget burning while retries hid the individual packet drops.

   Remediation

   • diverted all customer traffic from fra3 to other regions
   • connected each provider machine to the zrh1 cluster over Wireguard instead of the vSwitch
   • repaved every fra3 machine with a new identity, certificates and encryption-at-rest keys, dropping regional caches to recover faster
   • cloned existing datasets in a more distributed way to speed up repaving the machines
   • added machines back to the new region in batches and returned the region to the compute pool
   • redirected workloads away from zrh1 during the second outage
   • cloned the failing control plane node's key state to a higher-capacity node that took over its role and IP address

   Action items

   • Credit all instances that ran during the outages back to customers
   • Build up backup regions and solutions so a similar event has options that do not affect customers

   Lessons

   Running hot with a delayed hardware delivery left no room to take a region out, so fixing a provider network fault turned into a global capacity shortage. After one outage the team was anchored on its cause and first looked for network problems in the second outage, which had a different cause: a control plane node whose disk could not keep up with the Kubernetes change rate.

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2. IL-0154 Line cards on an SFO3 core router rebooted together and halved backbone capacity, and DOKS nodes whose guest networking did not recover stayed NotReady with degraded API servers until all affected nodes in the SFO3 DOKS fleet were recycled

   DigitalOcean2024

   Symptoms

   From 22:25 to 22:50 UTC every DigitalOcean service in the SFO3 region had network connectivity problems, as traffic between the datacenter and the backbone dropped. Traffic through the router was back by 22:30 and SFO3's control plane systems had reconnected by 22:50, and most services recovered then.

   Node NotReadyControl plane unresponsiveIntermittent connection failures

   Trigger

   Most of the line cards on one SFO3 core router rebooted at the same time at 22:21 UTC because of hardware errors on the device.

   Root cause

   DNS or network fault

   Component

   Kubernetes API serverkubelet

   Contributing factor

   –

   Remediation

   • The crashed line cards came back online and traffic on the core router was restored
   • Manually recycled all affected nodes across the SFO3 DOKS fleet

   Action items

   • Work with the router vendor's support team to find the root cause of the line card crash
   • Upgrade software on the core routers in SFO3
   • Raise thresholds for automated remediation so affected nodes are restored without manual action

   Lessons

   A short network fault can leave Kubernetes nodes broken long after the network itself is healthy, when the guest networking on the machines does not recover by itself. Checking node health and the API servers after the network returns, and having automated remediation that is allowed to replace many nodes at once, shortens that tail.

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