# Drb communication problem and crash **URL:** \ **Category:** Ruby\ **Created:** [October 12, 2007, 8:00pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084 "2007-10-12T20:00:38Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 12, 2007, 8:00pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/1 "2007-10-12T20:00:38Z")
Hi, So first of all a little context of what I’m trying to do. I have Rails app that needs quite a bit of computation and I want to run the different queries in a number of different processes. To do so, I’m trying to implement the following system: Rails --\> Drb Query Dispatcher --\> Drb Query Runner Rails sends a job to the query dispatcher which load balances the jobs over serveral query runners. The whole system works and then suddenly hangs. When it hangs I get the following message on the Drb Query Dispatcher: message type 0x54 arrived from server while idle message type 0x44 arrived from server while idle message type 0x43 arrived from server while idle message type 0x5a arrived from server while idle Then I can see that there is still some action for some of the queries until it freezes completely. Did anyone encounter similar problems? Or knows where I could fine at least the signification of these messages? Thanks alot! I’ll be glad to give more information if needed. PS: I have tried to implement this with the Slave library but ran into even more trouble with logs just making nonsense (looked like some memory corruption somewhere) ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 12, 2007, 10:27pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/2 "2007-10-12T22:27:35Z")
On Oct 12, 2007, at 11:00 , Laurent Francioli wrote: > over serveral query runners. > > The whole system works and then suddenly hangs. When it hangs I get > the > following message on the Drb Query Dispatcher: > > message type 0x54 arrived from server while idle > message type 0x44 arrived from server while idle > message type 0x43 arrived from server while idle > message type 0x5a arrived from server while idle I don’t see where this message is coming from in DRb, or ruby. > Then I can see that there is still some action for some of the queries > until it freezes completely. > > Did anyone encounter similar problems? Or knows where I could fine at > least the signification of these messages? grep your code for ‘while idle’, that will help. ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 14, 2007, 11:27pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/3 "2007-10-14T23:27:12Z")
Hi, Thanks for your quick answer! Well the message definitely doesn’t come from my code. If it really doesn’t come from Drb neither Ruby, maybe it is a system message? Also, I’ve read your Seattle.rb presentation slides and on one of your slides you seem to say that ACL shouldnt be used and could cause deadlocks; is this right? I’m asking cause we’re using it in our system to restrain the accepted calls from the localhost only. Another thing I noticed is that my version not using the Slave lib actually does produce the same behavior (variables mix-up, etc). It looks like the communication between the server and clients has some troubles. I also noticed that the problems occur more often with increasing number of servers running. Hope that helps a bit… I’ll keep you posted if I get new clues or even better…a fix! Thanks! Laurent ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 15, 2007, 6:50pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/4 "2007-10-15T18:50:01Z")
So I finally found the problem! The message I repported actually came from Postgres. The problem was that I had a connection to the DB at the moment of the fork (both using the Slave lib and my own forking stuff). It seems that this was somehow passed onto the child processes and interfered with the child access to the DB. I’m not 100% sure why since the child processes were actually creating their own connections anyway. But I’m sure it came from there tho since it is completely stable now! Thanks alot for your quick reply! Laurent ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 15, 2007, 8:39pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/5 "2007-10-15T20:39:42Z")
On Oct 15, 2007, at 09:50 , Laurent Francioli wrote: > were actually creating their own connections anyway. > But I’m sure it came from there tho since it is completely stable now! If it still had the file descriptor open, it would be copied. ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 16, 2007, 6:44pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/6 "2007-10-16T18:44:34Z")
> I don’t recall, which URL? Ok, it’s really old…[http://blog.segment7.net/articles/2006/04/22/drb-an-introduction-and-overview](http://blog.segment7.net/articles/2006/04/22/drb-an-introduction-and-overview) and as I said earlier, since I only had the slides and not the commment on them I couldn’t be sure 🙂 Btw, really nice presentation! It find it pretty difficult to get good doc on Drb and that’s a great piece! Thanks, Laurent ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 16, 2007, 9:33pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/7 "2007-10-16T21:33:57Z")
On Oct 16, 2007, at 09:44 , Laurent Francioli wrote: > doc on Drb and that’s a great piece! > Ah, even with an ACL it is still possible for people to do bad stuff > to your DRb processes. ACLs by themselves won’t cause deadlocks, but > they can’t prevent malice. ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 15, 2007, 8:37pm UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/8 "2007-10-15T20:37:57Z")
On Oct 14, 2007, at 14:27 , Laurent Francioli wrote: > Thanks for your quick answer! Well the message definitely doesn’t come > from my code. If it really doesn’t come from Drb neither Ruby, > maybe it > is a system message? > > Also, I’ve read your Seattle.rb presentation slides and on one of your > slides you seem to say that ACL shouldnt be used and could cause > deadlocks; is this right? I’m asking cause we’re using it in our > system > to restrain the accepted calls from the localhost only. I don’t recall, which URL? ---
**Author:** ![renuplex](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f04885/32.png) [@renuplex](https://www.ruby-forum.com/u/renuplex)\ **Post date:** [October 17, 2007, 10:03am UTC](https://www.ruby-forum.com/t/drb-communication-problem-and-crash/117084/9 "2007-10-17T10:03:32Z")
Eric H. wrote: > On Oct 16, 2007, at 09:44 , Laurent Francioli wrote: > > > doc on Drb and that’s a great piece! > > Ah, even with an ACL it is still possible for people to do bad stuff > > to your DRb processes. ACLs by themselves won’t cause deadlocks, but > > they can’t prevent malice. Ok, thanks for the explanation! 🙂