Ruby Multithreading: making one thread wait for a signal from another

Question

In Ruby, I want to have two threads running at the same time, and want the background thread to periodically signal the foreground thread. How do I get the foreground thread to block until the background thread says 'go'? I can think of a few ways to do it, but am after the most appropriate, idiomatic Ruby method.

In code:

loop do  # background, thread 1
  sleep 3
  receive_input
  tell_foreground_input_is_ready # <-- how do I do this?
end

and

loop do  # foreground, thread 2
  wait_for_signal_from_background  # <-- how do I do this?
  do_something
end

(note: background may signal multiple times to the foreground. each time foreground finishes waiting, it resets backlog.)

Answer 1

You'd want to use conditional variables and mutexes, as per this page

Answer 2

Turns out this works quite nicely:

require 'thread'
queue = Queue.new
Thread.new do
  100.times do |i|
    sleep 1
    queue.enq i
  end
end

loop do
  print "waiting... "
  puts queue.deq      # this function blocks.
end