# Problem with concurrency **URL:** \ **Category:** Ruby\ **Created:** [July 29, 2010, 7:55am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373 "2010-07-29T07:55:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 7:55am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/1 "2010-07-29T07:55:24Z")
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. Some modules just don’t produce any results when the thread count is set higher than 1. I normally wouldn’t bother you with something so broad but I’ve been debugging this for 24 hours straight so I figured that someone else might have run to a similar problem and save me 24 more hours of debugging. Has anyone else had a similar experience? ---
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 9:15am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/2 "2010-07-29T09:15:48Z")
On 07/29/2010 07:55 AM, Tasos L. wrote: > list.) > > ``` > while( handle_interrupt( ) ) > > ``` > > 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 ---
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 9:30am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/3 "2010-07-29T09:30:35Z")
Robert K. wrote: > On 07/29/2010 07:55 AM, Tasos L. wrote: > > > list.) > > > > ``` > > while( handle_interrupt( ) ) > > > > ``` > > > > 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 Hi Robert, Thanks for the reply, however I didn’t see any errors. This is going to be a bitch to debug… ---
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 10:16am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/4 "2010-07-29T10:16:46Z")
Tasos L. wrote: > Robert K. wrote: > > > On 07/29/2010 07:55 AM, Tasos L. wrote: > > > > > list.) > > > > > > ``` > > > while( handle_interrupt( ) ) > > > > > > ``` > > > > > > 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 > > Hi Robert, > > Thanks for the reply, however I didn’t see any errors. > > This is going to be a bitch to debug… Huh…it seems that the problem was actually caused by the localhost webserver. My laptop had a crazy uptime and all its memory (virtual and ram) had been somewhat exhausted. After a reboot everything started to work fine. I can’t believe all those hours of debugging went to waist. ---
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 11:47am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/5 "2010-07-29T11:47:39Z")
Robert K. wrote: > On 07/29/2010 10:16 AM, Tasos L. wrote: > > > > > Thread.abort\_on\_exception = true > > > > > > > > Then you will probably see errors. > > > I can’t believe all those hours of debugging went to waist. > > If it can happen once chances are that it will happen again. It’s > probably worth to dig a bit and try to find out what caused the memory > issue in the first place. Maybe you have a leaky application. What OS > btw? > > Kind regards > > robert Well, the laptop was on for 2-3 days constantly running fullscreen flash video, eclipse, apache2 & mysql ( being constantly hammered by Arachni due to the debugging itself) and around 13 tabs of Firefox spread over several windows. So in hindsight it’s not much of a surprise. I’m running the latest Kubuntu with Xfce, so I guess it has now become Xubuntu… ---
**Author:** ![zapotek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/z/3be4f8/32.png) [@zapotek](https://www.ruby-forum.com/u/zapotek)\ **Post date:** [July 29, 2010, 11:42am UTC](https://www.ruby-forum.com/t/problem-with-concurrency/192373/6 "2010-07-29T11:42:09Z")
On 07/29/2010 10:16 AM, Tasos L. wrote: > > > Thread.abort\_on\_exception = true > > > > > > Then you will probably see errors. > I can’t believe all those hours of debugging went to waist. If it can happen once chances are that it will happen again. It’s probably worth to dig a bit and try to find out what caused the memory issue in the first place. Maybe you have a leaky application. What OS btw? Kind regards robert