class Celluloid::IO::DNSResolver

Asynchronous DNS resolver using Celluloid::IO::UDPSocket

Constants

DNS_PORT
MAX_PACKET_SIZE

Maximum UDP packet we'll accept

Public Class Methods

generate_id() click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 15
def self.generate_id
  @mutex.synchronize { @identifier = (@identifier + 1) & 0xFFFF }
end
nameservers() click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 19
def self.nameservers
  Resolv::DNS::Config.default_config_hash[:nameserver]
end
new() click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 23
def initialize
  # early return for edge case when there are no nameservers configured
  # but we still want to be able to static lookups using #resolve_hostname
  @nameservers = self.class.nameservers or return

  @server = IPAddr.new(@nameservers.sample)

  # The non-blocking secret sauce is here, as this is actually a
  # Celluloid::IO::UDPSocket
  @socket = UDPSocket.new(@server.family)
end

Public Instance Methods

resolve(hostname) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 35
def resolve(hostname)
  if host = resolve_hostname(hostname)
    unless ip_address = resolve_host(host)
      fail Resolv::ResolvError, "invalid entry in hosts file: #{host}"
    end
    return ip_address
  end

  query = build_query(hostname)
  @socket.send query.encode, 0, @server.to_s, DNS_PORT
  data, _ = @socket.recvfrom(MAX_PACKET_SIZE)
  response = Resolv::DNS::Message.decode(data)

  addrs = []
  # The answer might include IN::CNAME entries so filters them out
  # to include IN::A & IN::AAAA entries only.
  response.each_answer { |name, ttl, value| addrs << value.address if value.respond_to?(:address) }

  return if addrs.empty?
  return addrs.first if addrs.size == 1
  addrs
end

Private Instance Methods

build_query(hostname) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 72
def build_query(hostname)
  Resolv::DNS::Message.new.tap do |query|
    query.id = self.class.generate_id
    query.rd = 1
    query.add_question hostname, Resolv::DNS::Resource::IN::A
  end
end
get_address(host) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 91
def get_address(host)
  Resolv::Hosts.new(host).getaddress
rescue
end
resolv() click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 68
def resolv
  @resolv ||= Resolv::Hosts.new
end
resolve_host(host) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 80
def resolve_host(host)
  resolve_ip(Resolv::IPv4, host) || get_address(host) || resolve_ip(Resolv::IPv6, host)
end
resolve_hostname(hostname) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 60
def resolve_hostname(hostname)
  # Resolv::Hosts#getaddresses pushes onto a stack
  # so since we want the first occurance, simply
  # pop off the stack.
  resolv.getaddresses(hostname).pop
rescue
end
resolve_ip(klass, host) click to toggle source
# File lib/celluloid/io/dns_resolver.rb, line 84
def resolve_ip(klass, host)
  klass.create(host)
rescue ArgumentError
end