How do I manage ruby threads so they finish all their work?

In ruby 1.9 (and 2.0), you can use ThreadsWait from the stdlib for this purpose:

require 'thread'require 'thwait'threads = []threads << Thread.new { }threads << Thread.new { }ThreadsWait.all_waits(*threads)

If you modify spawn_thread_for to save a reference to your created Thread, then you can call Thread#join on the thread to wait for completion:

x = Thread.new { sleep 0.1; print "x"; print "y"; print "z" }a = Thread.new { print "a"; print "b"; sleep 0.2; print "c" }x.join # Let the threads finish beforea.join # main thread exits...

produces:

abxyzc

(Stolen from the ri Thread.new documentation. See the ri Thread.join documentation for some more details.)

So, if you amend spawn_thread_for to save the Thread references, you can join on them all:

(Untested, but ought to give the flavor)

# main threadwork_units = Queue.new # and fill the queue...threads = []10.downto(1) do  threads << Thread.new do    loop do      w = work_units.pop      Thread::exit() if w.nil?      do_some_work(w)    end  endend# main thread continues while work threads devour workthreads.each(&:join)

Thread.list.each{ |t| t.join unless t == Thread.current }