From: Paul Tsung <ptsung@...>
Date: 2006-06-04T06:13:33+09:00
Subject: SizedQueue

Does anyone know about threads and SizedQueue?

I want to limit or control the number of threads created in a script.  I 
am not sure what is the best way to handle this.

I wrote a test script using SizedQueue to limit the number of threads.

require 'thread'

@items = %w{item1 item2 item3 item4 item5}
@queue = SizedQueue.new(1)
@thread = []
@nap = 3

def testthread(item)
	@thread << Thread.new(item) do | i |
	  puts Thread.list
		puts "#{i} will sleep for #{@nap} seconds"
		sleep(@nap)
		puts "#{i} woke up"
		@queue.deq
	end
end

@items.each do | item |
	@queue.enq( testthread(item) )
end

@thread.each { | th | th.join }

I set the SizedQueue max to one but the output I get is this.

#<Thread:0x28955c8>
#<Thread:0x28aa420>
item1 will sleep for 3 seconds
#<Thread:0x28aa420>
#<Thread:0x28955c8>
#<Thread:0x28aa0d8>
item2 will sleep for 3 seconds
item2 woke up
item1 woke up
#<Thread:0x28aa420>
#<Thread:0x28955c8>
#<Thread:0x28aa060>
item3 will sleep for 3 seconds
#<Thread:0x28aa060>
#<Thread:0x28955c8>
#<Thread:0x28a98f8>
item4 will sleep for 3 seconds
item4 woke up
item3 woke up
#<Thread:0x28955c8>
#<Thread:0x28a9b08>
item5 will sleep for 3 seconds
item5 woke up

The question is why are there three threads running concurrently from 
the output.  I know one is the main thread.  Then I expect only one 
other thread to be running.  Is this right or am I doing something 
wrong?

Thanks for any suggestions or input.

-- 
Posted via http://www.ruby-forum.com/.