Cases24 cases

4 to 8 of 24

1. IL-0348 Scaleway's FR-PAR region lost public internet connectivity when one 100 Gbps backbone link was saturated

   Scaleway2025

   Symptoms

   On 10 March 2025 at 16:22 UTC, public internet connectivity in Scaleway's FR-PAR region broke for all products. Most internet traffic between the FR-PAR-2 availability zone and the rest of the PAR region was blackholed for about five minutes, while VPC traffic and Dedibox RPN kept working.

   Packet lossService outageHigh latency

   Trigger

   While Scaleway's network team connected a new data center to the FR-PAR backbone, a human mistake in a router configuration rerouted more than 1 Tbps of traffic between OpCore DC3 and DC5 through a single 100 Gbps link.

   Root cause

   Operator error

   Component

   Backbone network (WAN)Object storageAuthoritative DNS servers and records

   Contributing factor

   Automation amplification

   Detection

   The router configuration error was detected quickly and rolled back within four minutes.

   Remediation

   • Rolled back the router configuration, restoring the correct configuration at 16:27 UTC

   Action items

   • Harden the peer review and production communication process for changes
   • Add failsafes and tests before network configuration is applied at backbone level
   • Deploy the fix for the Object Storage synchronisation software issue

   View case
2. IL-0257 canva.com went down for about 50 minutes when 1.5 million requests per second OOM-killed every API Gateway task

   Canva2024

   Symptoms

   On 12 November 2024, after a new version of Canva's editor was deployed at 8:47 AM UTC, the editor's object panel stayed in a perpetual loading state for many users, particularly in Asia. Then from 9:08 AM UTC to about 10:00 AM UTC canva.com was unavailable and all requests to it failed.

   Service outageOOMKilledHigh latencyPacket loss

   Trigger

   At 8:47 AM UTC a new version of the Canva editor page was deployed, and client devices began fetching its new static assets through Cloudflare while the network path between Cloudflare's Singapore and Ashburn locations was losing packets.

   Root cause

   Dependency failure

   Component

   CDN and edge networkAPI gatewayAmazon ECS

   Contributing factor

   Overlapping failuresMonitoring blind spotRetry stormAutomation amplificationUnpatched known bug

   Remediation

   • Added a temporary Cloudflare firewall rule at 9:29 AM UTC that blocked all traffic at the CDN so new API Gateway tasks could start
   • Redirected canva.com to the status page
   • Restored traffic gradually, starting with Australian users under strict rate limits

   Action items

   • Write a runbook for rerouting, blocking and progressively restoring traffic
   • Show users a more informative error page when canva.com is unavailable
   • Raise the baseline number of API Gateway tasks and the memory of each task
   • Add load shedding rules to the API Gateway for similar traffic patterns
   • Load test the API Gateway regularly
   • Deploy the patch for the thread-locking bug in the telemetry library
   • Add multithreaded tests for the contended code path to the telemetry library microbenchmark suite
   • Use page load completion events as a second canary indicator for page asset releases
   • Experiment with adding another rollout stage to the canary to give more time to detect issues
   • Add timeouts so user requests do not wait excessively long for assets
   • Work with Cloudflare to understand the system interactions behind the incident

   View case
3. IL-0347 About 25% of Scaleway FR-PAR-1 hypervisors lost VPC connectivity when both VPC BGP route reflectors got stuck

   Scaleway2024

   Symptoms

   On 18 October 2024, from 7:50 to 8:01 UTC, about 25% of the hypervisors in Scaleway's FR-PAR-1 availability zone lost VPC connectivity with the rest of the region, and products that use VPC failed with them. Public internet connectivity and Elastic Metal VPC connectivity were not affected.

   Network unreachablePacket lossNode NotReady

   Trigger

   At 6:20 UTC a Top of Rack switch in FR-PAR-1 had a software crash. One of the two BGP route reflectors for VPC ran on a hypervisor in that rack and was left in an abnormal state.

   Root cause

   Software defect

   Component

   Network control plane (SDN)BGP routingNetwork switchDatabaseManaged Kubernetes control plane and provider API

   Contributing factor

   Excessive blast radiusAutomation amplification

   Detection

   Health-check monitoring on both route reflectors detected the anomaly, and the Scaleway Customer Excellence and SRE teams detected the customer impact and opened an incident.

   Remediation

   • Fixed both VPC route reflectors by manual action

   Action items

   • Fixed the autohealing mechanism that had failed to fix route reflectors stuck in a stale state; the fix is https://github.com/FRRouting/frr/pull/17163
   • Run different software versions on the route reflectors so a single bug cannot stop several instances
   • Investigate the software issue that left the route reflectors in a stale state

   View case
4. IL-0440 Pods on Cybozu's Neco Kubernetes platform got frequent no such host and i/o timeout DNS errors from dropped packets

   Cybozu2024

   Symptoms

   A team using Neco, the Kubernetes platform run by Cybozu's Cloud Platform team, reported what looked like a performance problem in the cluster DNS servers. An application in a pod that resolved cluster Services at hundreds of requests per second frequently got `no such host` and `i/o timeout` errors.

   DNS resolution failuresIntermittent timeoutsPacket loss

   Trigger

   The number of MySQL clusters watched by the monitoring application increased, and after that the name resolution errors became frequent.

   Root cause

   Capacity exhaustion

   Component

   Linux kernelClient-side DNS resolver and cache

   Contributing factor

   Unreviewed defaults

   Detection

   A team using the platform contacted the Cloud Platform team, describing the errors as a performance problem in the cluster DNS server.

   Remediation

   • Raised the kernel parameter netdev_max_backlog on the nodes
   • Set up alerts on softnet
   • Wrote a runbook for the softnet alerts

   Action items

   • Evaluate Cilium's netkit device so pod packets bypass the backlog queue

   Lessons

   Raising netdev_max_backlog makes the same failure less likely and the new alerts catch it early, but it is not a root fix: a pod that sends more packets can fill the backlog queue again. Cybozu sees replacing the veth interface with netkit, which skips the backlog queue, as the root fix.

   View case
5. IL-0339 Azure Front Door and Azure CDN users saw intermittent connection errors, timeouts and latency spikes for hours

   Microsoft Azure2024

   Symptoms

   From 11:45 UTC on 30 July 2024, a subset of customers got intermittent connection errors, timeouts and latency spikes when connecting to Microsoft services that use Azure Front Door (AFD) and Azure Content Delivery Network (CDN). The Azure Portal team saw the first service degradation at 11:47 UTC.

   Intermittent connection failuresIntermittent timeoutsHigh latencyPacket loss

   Trigger

   Around 11:45 UTC the Azure network DDoS protection service was disengaging after a routine DDoS mitigation and returning traffic to its default routing to AFD, but the routes at one site in Europe could not be updated because the network control plane could not reach that site during a local power outage.

   Root cause

   Configuration change

   Component

   CDN and edge networkDDoS protection serviceNetwork control plane (SDN)Data center power and cooling

   Contributing factor

   Overlapping failuresExcessive blast radiusMonitoring blind spot

   Detection

   The Azure Portal team detected service degradation at 11:47 UTC and began to investigate. At 12:10 UTC network monitoring correlated the Portal incident to a network issue at one site in Europe, and networking engineers joined.

   Remediation

   • Rerouted traffic under the standard congestion playbook, which removed most of the impact by 13:58 UTC
   • Ordered the network control plane to reissue its commands to the misbehaving device, which could not be reached
   • Removed the device that kept attracting traffic from the network and scanned the network for other issues

   Action items

   • Add the missing configuration on network devices so a DDoS mitigation issue in one geography cannot spread to another
   • Improve validation and monitoring in the Azure network to detect invalid configurations
   • Improve monitoring for when the DDoS protection service is unreachable from the control plane but still serving traffic

   View case

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