# Asynchronous select from queue **URL:** \ **Category:** Ruby\ **Created:** [December 10, 2006, 9:50am UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900 "2006-12-10T09:50:32Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 10, 2006, 9:50am UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/1 "2006-12-10T09:50:32Z")
Please advise on how to implement multiple select from queues in Ruby. I have seen only selcet which operates on IO streams. I need to pass objects not symbols. I have 100 queues and I must wait when message appears on one of them. ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 10, 2006, 10:34am UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/2 "2006-12-10T10:34:53Z")
On Dec 10, 2006, at 24:50 , Boris Mojo-jojo wrote: > Please advise on how to implement multiple select from queues in > Ruby. I > have seen only selcet which operates on IO streams. I need to pass > objects not symbols. I have 100 queues and I must wait when message > appears on one of them. ri Queue ? – Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net) I LIT YOUR GEM ON FIRE! ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 10, 2006, 10:40am UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/3 "2006-12-10T10:40:55Z")
Eric H. wrote: > On Dec 10, 2006, at 24:50 , Boris Mojo-jojo wrote: > > > Please advise on how to implement multiple select from queues in > > Ruby. I > > have seen only selcet which operates on IO streams. I need to pass > > objects not symbols. I have 100 queues and I must wait when message > > appears on one of them. > > ri Queue ? > > – > Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net) > > I LIT YOUR GEM ON FIRE! Sorry but no info on select in ri. Look for yourslef C:\ruby\bin\>ri Queue ----------------------------------------------------------- Class: Queue This class provides a way to synchronize communication between threads. ``` Example: require 'thread' queue = Queue.new producer = Thread.new do 5.times do |i| sleep rand(i) # simulate expense queue << i puts "#{i} produced" end end consumer = Thread.new do 5.times do |i| value = queue.pop sleep rand(i/2) # simulate expense puts "consumed #{value}" end end consumer.join ``` * * * ## Class methods: ``` new ``` ## Instance methods: ``` <<, clear, deq, empty?, enq, length, num_waiting, pop, push, shift, size ``` ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 10, 2006, 6:15pm UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/4 "2006-12-10T18:15:30Z")
Boris Mojo-jojo wrote: > Sorry but no info on select in ri. Look for yourslef “select” only works on IO objects - that’s it’s purpose. The reason for pointing you to Queue was that you indicated you’re using queues, in which case the ri documentation is your best starting point. #select is in any case the completely wrong place to look unless you’ve implemented your queues as pipes or similar. If you want any more useful help you’ll need to give a more complete description of what you are trying to achieve. Vidar ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 11, 2006, 10:47am UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/5 "2006-12-11T10:47:09Z")
On 10.12.2006 18:12, Vidar H. wrote: > If you want any more useful help you’ll need to give a more complete > description of what you are trying to achieve. Adding to that, application architectural wise I do not see the benefit of having multiple queues if you want to read from all of them and treat objects identically anyway. This is a typical scenario where a single queue is sufficient and in fact the most efficient design. At the moment I cannot think of a reason why multiple queues must be there. Boris, can you elaborate? Kind regards ``` robert ``` ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 11, 2006, 12:06pm UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/6 "2006-12-11T12:06:56Z")
Robert K. wrote: > On 10.12.2006 18:12, Vidar H. wrote: > > > If you want any more useful help you’ll need to give a more complete > > description of what you are trying to achieve. > > Adding to that, application architectural wise I do not see the benefit > of having multiple queues if you want to read from all of them and treat > objects identically anyway. This is a typical scenario where a single > queue is sufficient and in fact the most efficient design. At the > moment I cannot think of a reason why multiple queues must be there. > Boris, can you elaborate? > > Kind regards > > robert Suppose you have 1000 devices which are being sent messages, every device has its own queue. devices are independent so the messages to them must be processed in parallel. Processing message in one device should not stop processing others. However as along as you cannot create 1000 threads, there is a thread pool where every thread waits for message to device X to arrive on one of the 1000 queues and processed it in context of device X. If some thread is processing message which was sent to device X then the queue X is excluded from thread pool to prevent parallel executing of message on the device by two different threads. You don’t want to use one queue, because when two messages are sent to one device one after another then all other messages will wait because second message will not be processed till first one is processed. Now once again the question. How do I do select from multiple queues? in Win32 there’s WaitForMultipleObjects in Java there’s Selector and Pipes in Ruby there’s ??? ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 11, 2006, 2:07pm UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/7 "2006-12-11T14:07:06Z")
Robert K. wrote: > On 11.12.2006 12:06, Boris Mojo-jojo wrote: > > > You don’t want to use one queue, because when two messages are sent to > > one device one after another then all other messages will wait because > > second message will not be processed till first one is processed. > > True, in that case “select” would help. But you can easily write your > own processor with thread pool. You can get ideas from Queue internals > or [http://wiki.rubygarden.org/Ruby/page/show/MultiThreading](http://wiki.rubygarden.org/Ruby/page/show/MultiThreading) > > Kind regards > > robert Thanks a lot for the link ---
**Author:** ![borisu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/7cd45c/32.png) [@borisu](https://www.ruby-forum.com/u/borisu)\ **Post date:** [December 11, 2006, 1:35pm UTC](https://www.ruby-forum.com/t/asynchronous-select-from-queue/78900/8 "2006-12-11T13:35:26Z")
On 11.12.2006 12:06, Boris Mojo-jojo wrote: > You don’t want to use one queue, because when two messages are sent to > one device one after another then all other messages will wait because > second message will not be processed till first one is processed. True, in that case “select” would help. But you can easily write your own processor with thread pool. You can get ideas from Queue internals or [http://wiki.rubygarden.org/Ruby/page/show/MultiThreading](http://wiki.rubygarden.org/Ruby/page/show/MultiThreading) Kind regards ``` robert ```