require 'drb/drb'
require 'monitor'
module DRb
# Timer id conversion keeps objects alive for a certain amount of time after
# their last access. The default time period is 600 seconds and can be
# changed upon initialization.
#
# To use TimerIdConv:
#
# DRb.install_id_conv TimerIdConv.new 60 # one minute
class TimerIdConv < DRbIdConv
class TimerHolder2 # :nodoc:
include MonitorMixin
class InvalidIndexError < RuntimeError; end
def initialize(timeout=600)
super()
@sentinel = Object.new
@gc = {}
@curr = {}
@renew = {}
@timeout = timeout
@keeper = keeper
end
def add(obj)
synchronize do
key = obj.__id__
@curr[key] = obj
return key
end
end
def fetch(key, dv=@sentinel)
synchronize do
obj = peek(key)
if obj == @sentinel
return dv unless dv == @sentinel
raise InvalidIndexError
end
@renew[key] = obj # KeepIt
return obj
end
end
def include?(key)
synchronize do
obj = peek(key)
return false if obj == @sentinel
true
end
end
def peek(key)
synchronize do
return @curr.fetch(key, @renew.fetch(key, @gc.fetch(key, @sentinel)))
end
end
private
def alternate
synchronize do
@gc = @curr # GCed
@curr = @renew
@renew = {}
end
end
def keeper
Thread.new do
loop do
alternate
sleep(@timeout)
end
end
end
end
# Creates a new TimerIdConv which will hold objects for +timeout+ seconds.
def initialize(timeout=600)
@holder = TimerHolder2.new(timeout)
end
def to_obj(ref) # :nodoc:
return super if ref.nil?
@holder.fetch(ref)
rescue TimerHolder2::InvalidIndexError
raise "invalid reference"
end
def to_id(obj) # :nodoc:
return @holder.add(obj)
end
end
end
# DRb.install_id_conv(TimerIdConv.new)
