main.rb

# threads dying on fork examples. run with:
#   ruby main.rb
# or
#   ruby main.rb fork
#
require 'thread'

class Worker
  def initialize
    @thread = Thread.new { work }
    @queue = Queue.new
  end

  def push(work)
    puts "[w] Is it alive? #{ @thread.alive? }"
    @queue << work
  end

  def work
    loop do
      puts "[w] Waiting for work..."
      work = @queue.pop
      break if work == :shutdown
      puts "[w] Working #{ work }"
    end
    puts "[w] Shut down!"
  end

  def shutdown!
    push(:shutdown)
  end
end

def main(worker)
  puts "[p] Forking..."
  sleep 5
  puts "[p] Pushing..."
  worker.push "work-1"
  sleep 5
  puts "[p] Pushing..."
  worker.push "work-2"
  sleep 5
  puts "[p] Shutting down..."
  worker.shutdown!
  sleep 5
  puts "[p] End!"
end

worker = Worker.new

if ARGV.first == "fork"
  puts "FORK TEST"
  fork { main(worker) }
  Process.waitall
else
  puts "REGULAR TEST"
  main(worker)
end

output.txt

~/P/f/thread-fork $ ruby main.rb fork
FORK TEST
[w] Waiting for work...
[p] Forking...
[p] Pushing...
[w] Is it alive? false
[p] Pushing...
[w] Is it alive? false
[p] Shutting down...
[w] Is it alive? false
[p] End!
~/P/f/thread-fork $ ruby main.rb
REGULAR TEST
[p] Forking...
[w] Waiting for work...
[p] Pushing...
[w] Is it alive? true
[w] Working work-1
[w] Waiting for work...
[p] Pushing...
[w] Is it alive? true
[w] Working work-2
[w] Waiting for work...
[p] Shutting down...
[w] Is it alive? true
[w] Shut down!
[p] End!