gistfile1.txt

➜  8549841 git:(master) ✗ ruby queues.rb
Popping before put
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
pushed 1
First pop after put...
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job: 1
  yielding: 1
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: [1]
Second pop after put...
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
➜  8549841 git:(master) ✗ ruby -v
ruby 1.9.3p448 (2013-06-27 revision 41675) [x86_64-darwin12.4.0]
➜  8549841 git:(master) ✗ chruby jruby                                                                                                              ➜  8549841 git:(master) ✗ ruby queues.rb
Popping before put
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
pushed 1
First pop after put...
popped: []
  popped job:
Second pop after put...  popped job:

  popped job:
  popped job:
  popped job:
  popped job: 1
  yielding: 1
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: [1]
➜  8549841 git:(master) ✗ gitx
➜  8549841 git:(master) ✗
➜  8549841 git:(master) git remote add myron https://gist.github.com/8550092.git
➜  8549841 git:(master) git push myron
fatal: You are pushing to remote 'myron', which is not the upstream of
your current branch 'master', without telling me what to push
to update which remote branch.
➜  8549841 git:(master) git push myron master
Username for 'https://gist.github.com': myronmarston
Password for 'https://[email protected]':
fatal: Authentication failed
➜  8549841 git:(master) cat queues.rb| pbcopy
➜  8549841 git:(master) chruby 1.9.3
➜  8549841 git:(master) ruby queues.rb
Popping before put
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
pushed 1
First pop after put...
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job: 1
  yielding: 1
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: [1]
Second pop after put...
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
➜  8549841 git:(master) chruby jruby
ruby qu	%                                                                                                                                                                                                                                                                                                                                                                   ➜  8549841 git:(master) ruby queues.rb
Popping before put
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
popped: []
pushed 1
First pop after put...
popped: []
Second pop after put...
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job: 1
  yielding: 1
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil
  popped job:
popped: [1]
  popped job:
  popped job:   popped job:   popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  popped job:
  yielding nil

queues.rb

#! /usr/bin/env ruby

@queues = 10.times.map { Array.new }

# An enumerator that yields `nil` if none of the queues has any items, but
# otherwise round-robins across them.
@foo = Enumerator.new do |enum|
  loop do
    found = false
    @queues.each do |queue|
      job = queue.pop
      puts "  popped job: #{job}"
      unless job.nil?
        found = true
        puts "  yielding: #{job}"
        enum.yield(job)
      end
    end

    puts "  yielding nil"
    enum.yield(nil) unless found
  end
end

# Pop up to 'count' objects from 
def pop(count)
  jobs = []
  while jobs.length < count
    job = @foo.next
    break if job.nil?
    jobs.push(job)
  end
  jobs
end

# First, verify that the there are no items available
puts "Popping before put"
puts "popped: #{pop(5)}"
@queues[5].push(1)
puts "pushed 1"
# Now, I'd expect the item to be immediately available after putting it, but in
# jRuby, it's not yielded until the second pop.

puts "First pop after put..."
puts "popped: #{pop(5)}"
puts "Second pop after put..."
puts "popped: #{pop(5)}"

# jruby 1.7.9 (1.9.3p392) 2013-12-06 87b108a on Java HotSpot(TM) 64-Bit Server VM 1.7.0_45-b18 [darwin-x86_64]
# Pop before put: []
# First pop after put: []
# Second pop after put: [1]

# ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]
# Pop before put: []
# First pop after put: [1]
# Second pop after put: []

# ruby 1.9.3p429 (2013-05-15 revision 40747) [x86_64-darwin13.0.0]
# Pop before put: []
# First pop after put: [1]
# Second pop after put: []