One Kubernetes Config Change Saved Cloudflare 600 Engineering Hours a Year

Cloud infrastructure giant Cloudflare disclosed in a blog post how a single-line configuration change to its Kubernetes environment eliminated 600 hours of annual engineering downtime. 

The adjustment addressed a recursive permission bottleneck that had caused the company’s infrastructure management tool, Atlantis, to stall for 30 minutes during every restart.

Atlantis, which Cloudflare uses to plan and apply Terraform changes across dozens of projects, runs as a singleton StatefulSet.

It relies on a Kubernetes Persistent Volume (PV) to maintain the state of its repositories. 

As the PV grew to contain millions of files, the 100 monthly restarts required for credential rotations and onboarding began to trigger 30-minute delays and false-alarm pages for on-call staff.

Internal investigations using system logs from the kubelet component—the node-level agent that coordinates pod creation—revealed that the delay occurred during volume mounting. 

By default, when a spec.securityContext includes an fsGroup, Kubernetes executes a recursive chgrp -R command to ensure the non-root process has permission to read and write to every file on the volume.

“This was ultimately caused by a safe default in Kubernetes that had silently become a bottleneck as the persistent volume used by Atlantis grew to millions of files," stated Braxton Schafer, the Cloudflare engineer who led the investigation.

Cloudflare resolved the issue by updating the ‘fsGroupChangePolicy’ field to ‘OnRootMismatch’, a feature available since Kubernetes version 1.20. 

This instructs the system to skip the recursive ownership check if the volume’s root directory already has the required permissions. 

Following the deployment, Atlantis restart times dropped from 30 minutes to approximately 30 seconds.

“For us, this one-line change to fsGroupChangePolicy reclaimed nearly 50 hours of blocked engineering time every month,” Schafer said. He noted that this was time teams had previously spent “waiting for infrastructure changes to go through, and time that on-call engineers had been spending responding to false alarms.”

The incident highlights a scalability challenge for platform engineers using standard Kubernetes configurations. 

While the software’s default settings provide a secure baseline for small workloads, they can generate significant overhead as data volumes increase. 

Cloudflare’s experience suggests that infrastructure teams should audit securityContext settings to prevent recursive permission updates from impacting service availability as their data footprints grow.