Find the best server (lowest ping loss and latency) from a list of servers

find-server.rb

#!/usr/bin/env ruby

require 'thread_safe'
require 'resolv'

exit 1 if Process.uid != 0

SERVERS = %w[
  site-g1.example.com
  site-g2.example.com
  site-p1.example.com
  site-p2.example.com
  site-p3.example.com
  site-s1.example.com
  site-s2.example.com
  site-s4.example.com
  site-k1.example.com
]

def default_route
  @default_router =
    begin
      route = `ip route | grep 'default via'`
      route.gsub('default', '')
    end
end

def nslookup(hostname, nameservers = ['114.114.114.114'])
  Resolv::DNS.new(nameserver: nameservers).getaddress(hostname).to_s
end

def ping(ip)
  # set default route
  system "ip route replace #{ip}/32 #{default_route}"

  result = `ping -i 0.2 -c 40 -n #{ip}`

  received = result[/(\d+) received/, 1].to_i
  avg = result[/\/([0-9\.]+)\//, 1].to_f

  {
    loss: 1.0 - received / 40.0,
    rtt: avg
  }
end

def find_best_server
  threads = []
  server_ping_results = ThreadSafe::Hash.new
  
  SERVERS.map do |server|
    thread = Thread.new do
      ip = nslookup(server)
      res = ping ip
      puts "#{server} (#{ip}) #{res}"
      server_ping_results[server] = res.merge(ip: ip)
    end
    threads.push thread
  end
  
  threads.each(&:join)
  
  # Find the best
  server, ping_result = server_ping_results.min_by do |k, v|
    v[:loss] * 1e10 + v[:rtt]
  end
  
  ip = ping_result[:ip]
  puts "Chosen: #{server} (#{ip})"
  
  # TODO
  raise 'Implement here'
end