daemonSet-dns-availability-check.yaml

# Disclaimer: 
# The provided YAML file is shared "as is" without any guarantees or warranties. Use it at your own risk.
# # This is an example and is provided as-is. Review and validate before deploying.
# This DaemonSet tests DNS resolution latency for mcr.microsoft.com against 3 DNS servers.
# Update the DNS server IPs on line 29 (DNS_SERVERS) to customise for your specific usage.
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: dns-availability-check
  labels:
    app: dns-check
spec:
  selector:
    matchLabels:
      app: dns-check
  template:
    metadata:
      labels:
        app: dns-check
    spec:
      containers:
      - name: dns-check
        image: mcr.microsoft.com/azurelinux/base/core:3.0
        command:
        - /bin/sh
        - -c
        - |
          curl -o /etc/yum.repos.d/azurelinux-prod-base.repo -L https://packages.microsoft.com/azurelinux/3.0/prod/base/x86_64/config.repo
          tdnf update -y
          tdnf install bind-utils gawk -y --nogpgcheck
          echo "Starting DNS availability check..."
          DNS_SERVERS="10.121.131.13 10.121.131.14 10.121.131.15"
          while true; do
            for dns in $DNS_SERVERS; do
              output=$(dig +stats +timeout=4 +tries=2 mcr.microsoft.com @"$dns" 2>&1)
              query_time=$(echo "$output" | grep "Query time" | awk '{print $4}')
              if [ -z "$query_time" ] || echo "$output" | grep -qi "timed out\|no servers\|connection refused"; then
                echo "$(date '+%Y-%m-%d %H:%M') TIMEOUT dns=$dns query_time=4000msec"
              elif [ "$query_time" -gt 2700 ]; then
                echo "$(date '+%Y-%m-%d %H:%M') SLOW dns=$dns query_time=${query_time}msec"
              fi
            done
            sleep 45
          done
        resources:
          requests:
            cpu: 50m
            memory: 32Mi
      restartPolicy: Always