JezK
Edit File: ring.rb
# # Note: Rinda::Ring API is unstable. # require 'drb/drb' require 'rinda/rinda' require 'thread' module Rinda ## # The default port Ring discovery will use. Ring_PORT = 7647 ## # A RingServer allows a Rinda::TupleSpace to be located via UDP broadcasts. # Service location uses the following steps: # # 1. A RingServer begins listening on the broadcast UDP address. # 2. A RingFinger sends a UDP packet containing the DRb URI where it will # listen for a reply. # 3. The RingServer receives the UDP packet and connects back to the # provided DRb URI with the DRb service. class RingServer include DRbUndumped ## # Advertises +ts+ on the UDP broadcast address at +port+. def initialize(ts, port=Ring_PORT) @ts = ts @soc = UDPSocket.open @soc.bind('', port) @w_service = write_service @r_service = reply_service end ## # Creates a thread that picks up UDP packets and passes them to do_write # for decoding. def write_service Thread.new do loop do msg = @soc.recv(1024) do_write(msg) end end end ## # Extracts the response URI from +msg+ and adds it to TupleSpace where it # will be picked up by +reply_service+ for notification. def do_write(msg) Thread.new do begin tuple, sec = Marshal.load(msg) @ts.write(tuple, sec) rescue end end end ## # Creates a thread that notifies waiting clients from the TupleSpace. def reply_service Thread.new do loop do do_reply end end end ## # Pulls lookup tuples out of the TupleSpace and sends their DRb object the # address of the local TupleSpace. def do_reply tuple = @ts.take([:lookup_ring, DRbObject]) Thread.new { tuple[1].call(@ts) rescue nil} rescue end end ## # RingFinger is used by RingServer clients to discover the RingServer's # TupleSpace. Typically, all a client needs to do is call # RingFinger.primary to retrieve the remote TupleSpace, which it can then # begin using. class RingFinger @@broadcast_list = ['<broadcast>', 'localhost'] @@finger = nil ## # Creates a singleton RingFinger and looks for a RingServer. Returns the # created RingFinger. def self.finger unless @@finger @@finger = self.new @@finger.lookup_ring_any end @@finger end ## # Returns the first advertised TupleSpace. def self.primary finger.primary end ## # Contains all discovered TupleSpaces except for the primary. def self.to_a finger.to_a end ## # The list of addresses where RingFinger will send query packets. attr_accessor :broadcast_list ## # The port that RingFinger will send query packets to. attr_accessor :port ## # Contain the first advertised TupleSpace after lookup_ring_any is called. attr_accessor :primary ## # Creates a new RingFinger that will look for RingServers at +port+ on # the addresses in +broadcast_list+. def initialize(broadcast_list=@@broadcast_list, port=Ring_PORT) @broadcast_list = broadcast_list || ['localhost'] @port = port @primary = nil @rings = [] end ## # Contains all discovered TupleSpaces except for the primary. def to_a @rings end ## # Iterates over all discovered TupleSpaces starting with the primary. def each lookup_ring_any unless @primary return unless @primary yield(@primary) @rings.each { |x| yield(x) } end ## # Looks up RingServers waiting +timeout+ seconds. RingServers will be # given +block+ as a callback, which will be called with the remote # TupleSpace. def lookup_ring(timeout=5, &block) return lookup_ring_any(timeout) unless block_given? msg = Marshal.dump([[:lookup_ring, DRbObject.new(block)], timeout]) @broadcast_list.each do |it| soc = UDPSocket.open begin soc.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, true) soc.send(msg, 0, it, @port) rescue nil ensure soc.close end end sleep(timeout) end ## # Returns the first found remote TupleSpace. Any further recovered # TupleSpaces can be found by calling +to_a+. def lookup_ring_any(timeout=5) queue = Queue.new Thread.new do self.lookup_ring(timeout) do |ts| queue.push(ts) end queue.push(nil) while it = queue.pop @rings.push(it) end end @primary = queue.pop raise('RingNotFound') if @primary.nil? @primary end end ## # RingProvider uses a RingServer advertised TupleSpace as a name service. # TupleSpace clients can register themselves with the remote TupleSpace and # look up other provided services via the remote TupleSpace. # # Services are registered with a tuple of the format [:name, klass, # DRbObject, description]. class RingProvider ## # Creates a RingProvider that will provide a +klass+ service running on # +front+, with a +description+. +renewer+ is optional. def initialize(klass, front, desc, renewer = nil) @tuple = [:name, klass, front, desc] @renewer = renewer || Rinda::SimpleRenewer.new end ## # Advertises this service on the primary remote TupleSpace. def provide ts = Rinda::RingFinger.primary ts.write(@tuple, @renewer) end end end if __FILE__ == $0 DRb.start_service case ARGV.shift when 's' require 'rinda/tuplespace' ts = Rinda::TupleSpace.new Rinda::RingServer.new(ts) $stdin.gets when 'w' finger = Rinda::RingFinger.new(nil) finger.lookup_ring do |ts2| p ts2 ts2.write([:hello, :world]) end when 'r' finger = Rinda::RingFinger.new(nil) finger.lookup_ring do |ts2| p ts2 p ts2.take([nil, nil]) end end end