Resolver outage alert before users notice
One public DNS resolver (1.1.1.1, 8.8.8.8) degrades for a region. Your site "is up" but half the users see "server not found" — the uptime monitor stays silent.
Recipe
#!/usr/bin/env bash
# Probe several resolvers for the same domain. If any one of them
# can't return an A-record under TIMEOUT seconds — alert.
DOMAIN=${1:?domain required}
TIMEOUT=${TIMEOUT:-2}
RESOLVERS=("1.1.1.1" "8.8.8.8" "9.9.9.9" "77.88.8.8")
for R in "${RESOLVERS[@]}"; do
if ! dig +time="$TIMEOUT" +tries=1 +short "@$R" "$DOMAIN" A >/dev/null; then
echo "Resolver $R failed for $DOMAIN at $(date -u)"
exit 1
fi
doneSame thing in Enterno.io
Enterno DNS tool already probes 8+ resolvers simultaneously (20+ on Pioneer+). The DNS monitor alerts the moment any one of them fails to return the record.
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