DNS resolver test - reports when DNS resolution is greater than 1 second

dns_resolver_test.sh

#!/bin/bash

if [[ -z $1 ]] || [[ $1 = "--help" ]]; then
    echo "Usage: $0 <resolver_ip> [<fqdn> [<docker_container>]]"
    exit 1
fi
resolver_ip=$1

record=shops.myshopify.com
if [[ -n $2 ]]; then
  record="$2"
fi

cmd=dig
if [[ -n $3 ]]; then
  cmd="docker exec $3 dig"
fi

count=0
errors=0
total_time=0
total_runs=0
echo "Starting test resolving $record with $resolver_ip at $(date)"

# Trap interrupt signal (Ctrl+C) to print summary
trap 'stop' INT

function stop() {
  end_time=$(date +%s.%N)
  total_time=$(echo "$end_time - $first_time" | bc)
  echo -e "\nSlow runs: $count, errors: $errors, total runs: $total_runs in $total_time seconds"
  exit 0
}

first_time=$(date +%s.%N)
while true; do
    start_time=$(date +%s.%N)

    # Run the dig command with the provided resolver IP address
    result=$($cmd "$record" A @"$resolver_ip" 2>&1)
    return_code=$?
    ((total_runs++))

    end_time=$(date +%s.%N)
    elapsed_time=$(echo "$end_time - $start_time" | bc)

    # Check if the command took longer than 1 second
    if (( $(echo "$elapsed_time > 1.0" | bc -l) )); then
        echo "$(date '+%Y-%m-%d %H:%M:%S') - Command took $elapsed_time seconds"
        ((count++))
    fi

    # Print the result if there was an issue (non-zero return code)
    if [ $return_code -ne 0 ]; then
        echo "Error ($return_code): $result"
        ((errors++))
    fi

    # Sleep for a moment before the next iteration
    sleep 1
done