Cases1 case

1 to 1 of 1

1. IL-0007 The AWS VPC CNI could not assign IP addresses to pods as an EKS cluster ran out of IPv4 space

   Adevinta2024

   Symptoms

   One evening the platform team that runs SCHIP, Adevinta's internal runtime platform on Kubernetes, was paged because some DaemonSets were failing. Checking the pod status showed this error from the network plugin: name="aws-cni" failed (add): add cmd: failed to assign an IP address to container

   IP address exhaustionPods Pending

   Trigger

   Not stated for the first page. It came in June, during the migration from SCHIP's kube-aws-based clusters to EKS-based clusters; the write-up mentions spikes of pods, such as a job that goes rogue or failing jobs that keep their IPs, as ways a cluster can run out.

   Root cause

   Capacity exhaustion

   Component

   AWS VPC CNIVPC subnet or pod address rangeKarpenter

   Contributing factor

   Unreviewed defaultsNo capacity planning

   Detection

   A pager alert that some DaemonSets were failing. The on-call engineer checked the pod status and found the aws-cni error about failing to assign an IP address.

   Remediation

   • Rolled out VPC CNI custom networking with a secondary CIDR to the smaller clusters from late August
   • Paused the EKS migration in September while available IPs were very low
   • Rolled out custom networking to the rest of the fleet
   • Added the --reserved-enis parameter to the Karpenter deployment

   Action items

   • Use VPC CNI custom networking with a secondary CIDR across the whole fleet
   • Make Karpenter account for custom networking with the --reserved-enis parameter

   Lessons

   For a platform team, the VPC CNI is not ready to scale in production without time spent on capacity planning, and every option has its pros and cons. For large clusters started today, IPv6 is the cheaper and more future-proof option. Do not assume that what works in small clusters will keep working when they grow.

   View case

By root cause1