Overview

Node Local DNS Cache improves DNS performance in Kubernetes by caching DNS queries locally on each node. Below are the steps to deploy Node Local DNS in an Amazon EKS cluster.

DNS query workflow with NodeLocal DNSCache.

flowchart LR
  A["Pod DNS Query"] --> B["NodeLocal DNSCache"]
  B --> C{"Cache Hit?"}
  C -->|Yes| D["Return Cached Result"]
  C -->|No| E{"Query Type?"}
  E -->|Local Domain| F["CoreDNS"]
  E -->|Reverse DNS| F
  E -->|External| G["VPC DNS Resolver"]
  F --> H["Response to Pod"]
  G --> H

Installation

Prepare a manifest similar to the sample nodelocaldns.yaml and save it as nodelocaldns.yaml.

wget https://raw.githubusercontent.com/kubernetes/kubernetes/master/cluster/addons/dns/nodelocaldns/nodelocaldns.yaml

Modify the default parameters in the template:

PILLAR__DNS__SERVER=$(kubectl get svc kube-dns -n kube-system -o jsonpath={.spec.clusterIP})

sed -i "s/__PILLAR__LOCAL__DNS__/169.254.20.10/g; s/__PILLAR__DNS__DOMAIN__/cluster.local/g; s/__PILLAR__DNS__SERVER__/$PILLAR__DNS__SERVER/g" nodelocaldns.yaml

The __PILLAR__CLUSTER__DNS__ and __PILLAR__UPSTREAM__SERVERS__ parameters do not need to be replaced in the template.

Apply the template:

kubectl apply -f nodelocaldns.yaml

Check if the NodeLocal DNSCache pods are running:

kubectl get pods -n kube-system | grep node-local-dns
node-local-dns-2mq4b                                         1/1     Running   0          24m
node-local-dns-44tbj                                         1/1     Running   0          24m
node-local-dns-8h9mc                                         1/1     Running   0          24m
node-local-dns-9fr7r                                         1/1     Running   0          24m
node-local-dns-9ltws                                         1/1     Running   0          24m
node-local-dns-j65bw                                         1/1     Running   0          24m
node-local-dns-mdxcc                                         1/1     Running   0          24m
node-local-dns-qssqs                                         1/1     Running   0          23m
node-local-dns-xc89s                                         1/1     Running   0          24m
node-local-dns-z6jqj                                         1/1     Running   0          24m
node-local-dns-zww2l                                         1/1     Running   0          24m

Key Improvements

Latency: DNS queries now resolve in ~0-1ms (local cache) vs 5-10ms (upstream) Resource Usage: CoreDNS CPU/Memory significantly reduced Stability: Fewer conntrack entries and UDP connections Scalability: CoreDNS can handle cluster growth without being overwhelmed

References