DNS is one of the Kubernetes core systems and can quickly become a source of issues when you’re running clusters at scale. For over a year at Datadog, we’ve run Kubernetes clusters with thousands of nodes that host workloads generating tens of thousands of DNS queries per second. It wasn’t easy to build an architecture able to handle this load, and we’ve had our share of problems along the way.

This talk starts with a presentation of how Kubernetes DNS works. It then dives into the challenges we’ve faced, which span a variety of topics related to load, connection tracking, upstream servers, rolling updates, resolver implementations, and performance. We then show how our DNS architecture evolved over time to address or mitigate these problems. Finally, we share our solutions for detecting these problems before they happen—and identifying misbehaving clients.