ConcurrentQueue

This is a Ruby gem that can be used to listen to multiple queues concurrently and return the value of the first queue to have an item pushed to it.

Install

gem install concurrent_queue

Documentation

You can use ConcurrentQueue instances as you would the core Queue instances. However, only the methods pop, push and length have been implemented. If you want to use this gem and you need more of the core methods feel free to submit a pull request or simply open an issue.

The ConcurrentQueue class also offers a new method pop. Call this with a ConcurrentQueue instance or Array of ConcurrentQueue instances and it will listen to all the queues simultaneously. It will immediately return a pre existing item found in any of the queues if found, otherwise it will reutrn the first item pushed to any of the queues. Just like regular queues, the order of items in each individual queue is preserved, however, if a pre existing item is found it will be popped from the earliest queue in the array you provide.

Example

require 'concurrent_queue'

q1 = ConcurrentQueue.new
q2 = ConcurrentQueue.new

t1 = Thread.new do
  puts ConcurrentQueue.pop([q1,q2])
  sleep 2
  puts ConcurrentQueue.pop([q1,q2])
end

t2 = Thread.new do
  sleep 1
  puts ConcurrentQueue.pop([q1,q2])
  sleep 2
  puts ConcurrentQueue.pop([q1,q2])
end

sleep 0.5
q1.push(1)
q1.push(2)
q2.push(3)
q2.push(4)
t1.join
t2.join