From: Robert Klemme <shortcutter@...>
Date: 2010-07-29T16:15:09+09:00
Subject: Re: Problem with concurrency

On 07/29/2010 07:55 AM, Tasos Laskos wrote:
> Hi guys,
>
> I'm having an issue with a multi-threaded system I'm developing.
>
> Sorry if my question sounds too generic and unspecific but:
> Are there any known pitfalls that one might come across when using
> threads?
>
> This is the code that runs the threads:
> (I'm new to this so the code is borrowed from another post from this
> list.)
> ---------
>      def run_mods( page_data, structure )
>
>          mod_queue = Queue.new
>
>          @threads = ( 1..@opts[:threads] ).map {
>              |i|
>              Thread.new( mod_queue ) {
>                  |q|
>                  until( q == ( curr_mod = q.deq ) )
>
>                      if( !run_module?( curr_mod , structure ) )
>                          print_verbose( 'Skipping ' + curr_mod.to_s +
>                              ', nothing to audit.' )
>                          next
>                      end
>
>                      print_debug( )
>                      print_debug( 'Thread-' + i.to_s + " " +
> curr_mod.inspect )
>                      print_debug( )
>
>                      print_status( curr_mod.to_s )
>
>                      mod_new = curr_mod.new( page_data, structure )
>
>                      mod_new.prepare   if curr_mod.method_defined?(
> 'prepare' )
>                      mod_new.run
>                      mod_new.clean_up  if curr_mod.method_defined?(
> 'clean_up' )
>
>                      while( handle_interrupt(  ) )
>                      end
>
>                  end
>              }
>          }
>
>          # enque the loaded mods
>          for mod in ls_loaded_mods
>              mod_queue.enq mod
>          end
>
>          @threads.size.times { mod_queue.enq mod_queue }
>          @threads.each { |t| t.join }
>
>      end
> -----------------
>
> The modules call their parent and the parent uses Net::HTTP.
> Then they get the HTTP response via the parent and manipulate it in some
> way.
> My main problem is that from what I've gathered some HTTP calls fail
> without an error.

Try this at the top of your program:

Thread.abort_on_exception = true

Then you will probably see errors.

Kind regards

	robert

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