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#
# 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