I need a "rolling timeout" for some code. If something doesn't happen for x seconds, timeout, but if it does, reset the timer. The Ruby Timeout module doesn't help with this, it provides only a static timeout.

api.rb

# The API I thought up, This example will
# sleep for 16 seconds (4 * 4 seconds + 5 seconds)
 
begin
	RollingTimeout.new(5) {|timer|
		sleep(4)
		timer.reset
		sleep(4)
		timer.reset
		sleep(4)
		timer.reset
		sleep(4)
		timer.reset
		sleep(6) # This will timeout
		end
	}
rescue 
	# Do something
	puts "Timed out!"
end

output.txt

$ ruby rolling_timeout.rb 
Rolling timout window open for 5 seconds total
Rolling timout window open for 10 seconds total
Rolling timout window open for 15 seconds total
Rolling timout window open for 20 seconds total
Rolling timout window open for 25 seconds total
That was the last item on the queue, the pop will now timeout in 5 seconds
Rolling timout window open for 30 seconds total
Timed out!

possible_solution.rb

# A working solution. I'm not sure I like
# the thread destruction/creation. See
# output.txt for the output.

require 'timeout'
require 'thread'
 
class RollingTimeout
	attr_accessor :code_thread
	def initialize(time_in_seconds, &block)
		@time_in_seconds = time_in_seconds
		start
		@timed_out = false
		@code_thread = Thread.new{ yield self }
		@code_thread.join
		@timer_thread.join if @timed_out
	end
	
	def reset
		stop
		start
	end

	def stop
		@timer_thread.kill
	end

	def start
		@timer_thread = new_timer_thread
	end
		
	private
 
	def new_timer_thread
		Thread.new {
			sleep(@time_in_seconds)
			@timed_out = true
			@code_thread.kill
			raise Timeout::Error
		}
	end
end
 
data_queue = Queue.new
3.times { data_queue << Proc.new {sleep(0.09)} }
data_queue << Proc.new {sleep(0.09); puts "That was the last item on the queue, the pop will now timeout in 0.1 seconds"}

begin
	slept_for = 0
	x = RollingTimeout.new(0.1) {|timer|
		while data = data_queue.pop do
			data.call
			puts "Rolling timout window open for #{slept_for += 0.09} seconds total"
			timer.reset
		end
	}
rescue Timeout::Error
	puts "Timed out!"
end

loop do
  timeout 4 do
    if data = data_queue.pop
      data.call
    else
      break
    end
  end
end

You need to start the @code_thread and set @timed_out before starting @timer_thread, or you've got a race.

I was going to suggest doing away with @code_thread and just yielding so the code in the block happens on the same thread as that outside it, but that would mean using a Thread#raise in the @timeout_thread which might accidentally get caught by the user code...