Asynchronous DNS Resolution

RubyDNS can be used as an asynchronous DNS client, either passing requests to a specific server or using default system resolvers.

# There technically should be at least one nameserver:
resolver = RubyDNS::Resolver.new(RubyDNS::System::nameservers)

EventMachine::run do
	resolver.query('google.com') do |response|
		assert_equal RubyDNS::Message, response.class
		assert_equal Resolv::DNS::RCode::NoError, response.rcode

		EventMachine::stop
	end
end

EventMachine provides the basic asynchronous event processing loop, and thus any use of RubyDNS::Resolver must happen within a valid EventMachine context.

Timeout

As this is an asynchronous service, a timeout can be provided (the default is 5 seconds). If a response is not received within a given time, a RubyDNS::ResolutionFailure error will be returned to the caller in the response argument:

SERVERS = [[:udp, '127.0.0.1', 5330], [:tcp, '127.0.0.1', 5330]]
resolver = RubyDNS::Resolver.new(SERVERS, :timeout => 60)

For more examples, please check out rubydns/test/test_slow_server.rb.

Logging

Additional debugging output can be sent to a log file by providing the :logger option:

require 'logger'

SERVERS = [[:udp, '127.0.0.1', 5330], [:tcp, '127.0.0.1', 5330]]
resolver = RubyDNS::Resolver.new(SERVERS, :logger => Logger.new($stderr))