Refresh Machine

Hello,

Recently I had to deal with external data sources that had to be
refresh every now and then. Instead of using an infinite loop inside a
thread for every object, I used Queue to create a “Refresh Machine”.
Below is the code… my questions are: can it be improved? is there
another way to do the same?

Thanks

Pablo

require ‘thread’
class RefreshMachine

attr_accessor :wait

def initialize(wait = false)
@wait = wait
@killall = false
@queue = Queue.new
@removed = Array.new
@thread = Thread.new do
loop do
( @removed.clear; @queue.clear; @killall = false ) if @killall
next if @queue.empty?
object, last_refresh, thread = @queue.deq

     # Helps the garbage collection
     thread = nil if (! thread.nil?) and (! thread.alive?)

     # Three things can happen with a dequeued object
     if (Time.now < (last_refresh + object.refresh)) or
        (! thread.nil? and @wait)
       # First: It's too early to refresh it or we still have
       #        a refresh thread running and have to 'wait', so we
       #        just put it back in the queue
       @queue.enq [ object, last_refresh, thread ]
     else
       if @removed.include?(object)
         # Second: We have a "remove request" for it, so we
         #         delete the request and avoid queueing it again
         @removed.delete(object)
       else
         # Third: It's time to refresh it, so we
         #        call do_refresh and put it back in the queue
         add(object)
       end
     end
   end
 end

end

def add(object)
@queue.enq [ object, Time.now, Thread.new { object.do_refresh } ]
end

def del(object)
@removed << object unless @removed.include?(object)
end

def killall
@killall = true
end

end # of class RefreshMachine

Great code. You forgot to mention that “object” should implement
#refresh and #do_refresh. The second is easy to understand (something
that does the refresh), but the first I am not sure… is it a time
interval?

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