Module: EventMachine::DnsCache

Defined in:
lib/em/dns_cache.rb

Defined Under Namespace

Classes: Cache, MxQuery, Request, Socket

Class Method Summary collapse

Class Method Details

.add_cache_entry(cache_type, domain, value, expiration) ⇒ Object 



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# File 'lib/em/dns_cache.rb', line 48

def self.add_cache_entry cache_type, domain, value, expiration
	cache = if cache_type == :mx
		@mx_cache
	elsif cache_type == :a
		@a_cache
	else
		raise "bad cache type"
	end

	v = EM::DefaultDeferrable.new
	v.succeed( value.dup.freeze )
	cache.add domain, v, expiration
end

.add_nameserver(ns) ⇒ Object 



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# File 'lib/em/dns_cache.rb', line 39

def self.add_nameserver ns
	@nameservers << ns unless @nameservers.include?(ns)
end

.lazy_initialize ⇒ Object 



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# File 'lib/em/dns_cache.rb', line 165

def self.lazy_initialize
	# Will throw an exception if EM is not running.
	# We wire a signaller into the socket handler to tell us when that socket
	# goes away. (Which can happen, among other things, if the reactor
	# stops and restarts.)
	#
	raise "EventMachine reactor not running" unless EM.reactor_running?

	unless @u
		us = proc {@u = nil}
		@u = EM::open_datagram_socket( "0.0.0.0", 0, Socket ) {|c|
			c.unbind_signaller = us
		}
	end

end

.parse_local_mx_records(txt) ⇒ Object 



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# File 'lib/em/dns_cache.rb', line 183

def self.parse_local_mx_records txt
	domain = nil
	addrs = []

	add_it = proc {
		a = addrs.sort {|m,n| m.last <=> n.last}.map {|y| y.first}
		add_cache_entry :mx, domain, a, -1
	}

	txt = StringIO.new( txt ) if txt.is_a?(String)
	txt.each_line {|ln|
		if ln =~ /\A\s*([\d\w\.\-\_]+)\s+(\d+)\s*\Z/
			if domain
				addrs << [$1.dup, $2.dup.to_i]
			end
		elsif ln =~ /\A\s*([^\s\:]+)\s*\:\s*\Z/
			add_it.call if domain
			domain = $1.dup
			addrs.clear
		end
	}

	add_it.call if domain
end

.resolve(domain) ⇒ Object

Needs to be DRYed up with resolve_mx.



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# File 'lib/em/dns_cache.rb', line 64

def self.resolve domain
	if d = @a_cache.retrieve(domain)
		d
	else
=begin
		d = @a_cache[domain]
		if d.first < Time.now
			$>.puts "Expiring stale cache entry for #{domain}" if @verbose
			@a_cache.delete domain
			resolve domain
		else
			$>.puts "Fulfilled #{domain} from cache" if @verbose
			d.last
		end
	else
=end
		$>.puts "Fulfilling #{domain} from network" if @verbose
		d = EM::DefaultDeferrable.new
		d.timeout(5)
		@a_cache.add domain, d, 300 # Hard-code a 5 minute expiration
		#@a_cache[domain] = [Time.now+120, d] # Hard code a 120-second expiration.

		lazy_initialize
		m = Resolv::DNS::Message.new
		m.rd = 1
		m.add_question domain, Resolv::DNS::Resource::IN::A
		m = m.encode
		@nameservers.each {|ns|
			@message_ix = (@message_ix + 1) % 60000
			Request.new d, @message_ix
			msg = m.dup
			msg[0,2] = [@message_ix].pack("n")
			@u.send_datagram msg, ns, 53
		}

		d.callback {|resp|
			r = []
			resp.each_answer {|name,ttl,data|
				r << data.address.to_s if data.kind_of?(Resolv::DNS::Resource::IN::A)
			}

			# Freeze the array since we'll be keeping it in cache and passing it
			# around to multiple users. And alternative would have been to dup it.
			r.freeze
			d.succeed r
		}


		d
	end
end

.resolve_mx(domain) ⇒ Object

Needs to be DRYed up with resolve.



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# File 'lib/em/dns_cache.rb', line 119

def self.resolve_mx domain
	if d = @mx_cache.retrieve(domain)
		d
	else
=begin
	if @mx_cache.has_key?(domain)
		d = @mx_cache[domain]
		if d.first < Time.now
			$>.puts "Expiring stale cache entry for #{domain}" if @verbose
			@mx_cache.delete domain
			resolve_mx domain
		else
			$>.puts "Fulfilled #{domain} from cache" if @verbose
			d.last
		end
	else
=end
		$>.puts "Fulfilling #{domain} from network" if @verbose
		d = EM::DefaultDeferrable.new
		d.timeout(5)
		#@mx_cache[domain] = [Time.now+120, d] # Hard code a 120-second expiration.
		@mx_cache.add domain, d, 300 # Hard-code a 5 minute expiration

		mx_query = MxQuery.new d

		lazy_initialize
		m = Resolv::DNS::Message.new
		m.rd = 1
		m.add_question domain, Resolv::DNS::Resource::IN::MX
		m = m.encode
		@nameservers.each {|ns|
			@message_ix = (@message_ix + 1) % 60000
			Request.new mx_query, @message_ix
			msg = m.dup
			msg[0,2] = [@message_ix].pack("n")
			@u.send_datagram msg, ns, 53
		}



		d
	end

end

.verbose(v = true) ⇒ Object 



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# File 'lib/em/dns_cache.rb', line 43

def self.verbose v=true
	@verbose = v
end