kubecon25/content/day-1/04_dns-debugging.md

title, weight, tags

title	weight	tags
Understanding and Debugging DNS in Kubernetes Clusters	4	rejekts

{{% button href="https://www.youtube.com/watch?v=awXjABDknww" style="warning" icon="video" %}}Watch talk on YouTube{{% /button %}} {{% button href="https://github.com/mqasimsarfraz/talks/tree/main/CloudNativeRejekts-2025" style="tip" icon="person-chalkboard" %}}Slides{{% /button %}}

Baseline

DNS Components

graph LR
    Application-->NodeLocalDNS-->CoreDNS-->Upstream

Problems

• Many hidden systems
• Not easy to trace across clusters

Tools

Demo queries are located in the slides and were executed during the stream

CoreDNS Log Plugin

• Core-Plugin (just needs to be activated)
• Logs all requests to stdout

Hubble

• Cilium observability needs cilium l7 proxy, runs as deamonset
• Needs CiliumNetworkPolicies for AppPod and CoreDNS
• Metrics, UI and cli with jq (and protocol filter)

Inspector Gadget

• Toolset for Kubernetes and Linux that can be customized
• Runns as daemonset or debug pod - gadgets are distributed as containers (via artifactorhub)
• DNS-Gadget: Trace via ebpf, post process with wasm

Overview

• CoreDNS: Great for initial, nut only CoreDNS
• Hubble: Compact overview, but cilium needed with special configs
• Inspector Gadget: Rich DNS traces, limited tcp support