Ruby Thread Condition Variables

 

线程同步使用条件变量（Condition Variables）

require 'monitor'

SONGS = [
	'Blue Suede Shoes',
	'Take Five',
	'Bye Bye Love',
	'Rock Around The Clock',
	'Ruby Tuesday'
]
START_TIME = Time.new

def timestamp
	(Time.now - START_TIME).to_i
end

# Wait for up to two minutee between customer requests
def get_customer_request
	sleep(120 * rand)
	song = SONGS.shift
	puts "#{timestamp}: Requesting #{song}" if song
	song
end

# Songs take between two and three minutes
def play(song)
	puts "#{timestamp}: Playing #{song}"
	sleep(120 + 60*rand)
end

ok_to_shutdown = false
# and here's our original code

playlist = []
playlist.extend(MonitorMixin)
plays_pending = playlist.new_cond

# Customer request thread
customer = Thread.new do
	loop do
		req = get_customer_request
		puts req
		break unless req
		playlist.synchronize do
			playlist << req
			plays_pending.signal
		end
	end
end

# Player Thread
player = Thread.new do
	loop do
		song = nil
		playlist.synchronize do
			break if ok_to_shutdown && playlist.empty?
			plays_pending.wait_while {playlist.empty?}
			song = playlist.shift
		end
		break unless song
		play(song)
	end
end

customer.join
ok_to_shutdown = true
player.join

 19: Requesting Blue Suede Shoes

Blue Suede Shoes

19: Playing Blue Suede Shoes

63: Requesting Take Five

Take Five

101: Requesting Bye Bye Love

Bye Bye Love

149: Playing Take Five

169: Requesting Rock Around The Clock

Rock Around The Clock

215: Requesting Ruby Tuesday

Ruby Tuesday

 

269: Playing Bye Bye Love

428: Playing Rock Around The Clock

574: Playing Ruby Tuesday