# Deadlocks in Drb Server

**URL:** <https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117>\
**Category:** Ferret\
**Created:** [October 2, 2007, 4:13pm UTC](https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117 "2007-10-02T16:13:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![turnkeytraders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ba8739/32.png) [@turnkeytraders](https://www.ruby-forum.com/u/turnkeytraders)\
**Post date:** [October 2, 2007, 4:13pm UTC](https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117/1 "2007-10-02T16:13:47Z")

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Hi,

we still have the problem in that the Ferret Drb server dies on us  
sometimes. Looking through ferret\_server.out and we come accross this:

deadlock 0xb7261cb0: sleep:F(1012) - /usr/lib/ruby/1.8/drb/drb.rb:566  
deadlock 0xb71d8654: sleep:F(409) - /usr/lib/ruby/1.8/drb/drb.rb:566  
deadlock 0xb723f3e0: sleep:F(7) - /usr/lib/ruby/1.8/drb/drb.rb:566  
deadlock 0xb72607c0: sleep:F(11) - /usr/lib/ruby/1.8/drb/drb.rb:566  
deadlock 0xb7d44754: sleep:J(0xb71fab64) (main) -  
/var/www/web1/oms/current/script/ferret\_start:70  
deadlock 0xb71fab64: sleep:F(6) - /usr/lib/ruby/1.8/drb/drb.rb:944  
deadlock 0xb726f158: sleep:S - /usr/lib/ruby/1.8/drb/drb.rb:626  
/usr/lib/ruby/1.8/drb/drb.rb:626: Thread(0xb726f158): deadlock (fatal)

Anyone have an idea what may be causing the problem and what we can do  
to get round it?

Thanks

Matthew

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<div class="post-metadata">

**Author:** ![turnkeytraders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ba8739/32.png) [@turnkeytraders](https://www.ruby-forum.com/u/turnkeytraders)\
**Post date:** [October 2, 2007, 5:50pm UTC](https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117/2 "2007-10-02T17:50:52Z")

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Hey …

do you have very high load on your drb? I serialize  
my indexing requests and did not yet have a deadlock,  
but then again, i’m not using aaf … afaik, aaf uses  
separate threads to add documents to the index, so  
there _might_ be a problem when you have a really  
high load… but that’s just speculation …

can you provide us with more information about the  
circumstances?

Ben

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**Author:** ![turnkeytraders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ba8739/32.png) [@turnkeytraders](https://www.ruby-forum.com/u/turnkeytraders)\
**Post date:** [October 3, 2007, 2:05pm UTC](https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117/3 "2007-10-03T14:05:16Z")

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On Tue, Oct 02, 2007 at 04:13:47PM +0200, Matthew L.ham wrote:

> /var/www/web1/oms/current/script/ferret\_start:70  
> deadlock 0xb71fab64: sleep:F(6) - /usr/lib/ruby/1.8/drb/drb.rb:944  
> deadlock 0xb726f158: sleep:S - /usr/lib/ruby/1.8/drb/drb.rb:626  
> /usr/lib/ruby/1.8/drb/drb.rb:626: Thread(0xb726f158): deadlock (fatal)
> 
> Anyone have an idea what may be causing the problem and what we can do  
> to get round it?

To be honest, I have no idea where this might come from - this trace  
looks like it would be worth an email to DRb’s author.

As Ben wrote, changing the way the DRb server works might help to  
prevent this.

Option 1) would be to synchronize all calls to the DRb server’s methods,  
#method\_missing in ferret\_server.rb would be a good place to implement  
this. Performance will suffer, but it might be worth a try.

Option 2) is how we did it in [omdb.org](http://omdb.org)’s DRb server - queue all indexing  
requests and work through the queue in a separate thread. [Omdb.org](http://Omdb.org) uses  
local IndexSearcher instances to save the DRb server from handling  
search.

Cheers,  
Jens

PS: There are plans to give aaf and especially the DRb server a major  
overhaul, and to incorporate several of the ideas from the [omdb.org](http://omdb.org)  
solution. However this won’t be ready before November, I guess.

–  
Jens Krämer  
[http://www.jkraemer.net/](http://www.jkraemer.net/) - Blog  
[http://www.omdb.org/](http://www.omdb.org/) - The new free film database

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<div class="post-metadata">

**Author:** ![turnkeytraders](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/ba8739/32.png) [@turnkeytraders](https://www.ruby-forum.com/u/turnkeytraders)\
**Post date:** [October 4, 2007, 11:50am UTC](https://www.ruby-forum.com/t/deadlocks-in-drb-server/116117/4 "2007-10-04T11:50:07Z")

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Thanks for the tips guys. We’ll look closer and see if we can come up  
with more specific details on when this happens.

At the moment we have low load on the system but call rebuild\_index  
every now and again. Our guess is that this may be causing the problems

- but again, we’ll give it a closer look.

Matthew