Dns defaults in kuberbetes
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www.linkedin.com#kubernetes #devops #dns #observability #performance #networking #kubedns… | Adam Danko | 24 commentairesThe Kubernetes default that cost us performance:
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In Kubernetes, 'ndots:5' is set by default in '/etc/resolv.conf'.
This means every hostname with fewer than 5 dots goes through every search domain - before even trying the actual FQDN.
So when your app tries to resolve 'example.com', it might actually generate multiple DNS queries like:
'example.com.svc.cluster.local'
'example.com.google.internal'
'example.com.cluster.local'
'example.com'
Each failed lookup = latency, DNS noise, and pointless retries.
🔍 As Tim Hockin (Kubernetes co-founder) explained back in 2016:
“This is a tradeoff between automagic and performance.”
The default 'ndots:5' isn’t about optimization - its about making things “just work” across SRV records, multi-namespace service lookups, and what were then called PetSets (now StatefulSets).
Even if it means triggering multiple DNS lookups before hitting the actual domain.
So yes - it comes at a performance cost.
✅ What are the possible workarounds?
- Use FQDNs ("my-service.my-namespace.svc.cluster.local.") - dont forget the trailing dot to skip search paths
- Lower the 'ndots' value with dnsConfig at the pod level or at a wider level using policy engines (Gatekeeper, Kyverno)
- Reduce unnecessary search domains in your cluster setup
🔎 Real-world impact:
After lowering ndots, we saw a clear drop in both conntrack table usage and application latency - confirming the reduction in DNS query volume and retries.
(Image attached - green, yellow, and blue lines are the nodes with kube-dns on them.)
The impact is most noticeable if your workloads involves:
- Low-latency demands
- Constant DNS resolution
👉 Have you tuned your DNS settings - or just lived with the default?
What other Kubernetes defaults have surprised you in production?
(Source of Tim's comment: https://lnkd.in/dBVDeCCD)
#kubernetes #devops #dns #observability #performance #networking #kubedns #coredns #openshift | 24 commentaires sur LinkedIn
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