Ruby threading deadlocks

Question

I'm writing a project at the moment that involves running two parallel threads to pull data from different sources at regular intervals. I am using the Threads functionality in ruby 1.9 to do this but am unfortunately running up against deadlock problems. Also I have a feeling that the Thread.join method is causing the threads to queue rather than run in parallel.

I'm new to multithreading programming and any advice would be greatly appreciated

Cheers

Patrick

EDIT: The shared resource that both these threads are accessing is a mysql database which could be the problem. The deadlock arrises after a few iterations of these threads being run.

Answer 1

You can use synchronization mechanisms such as Mutex, Monitor, Queue, SizedQueue from standart library. Or problem in using them?

Answer 2

It's very difficult to diagnose what could be going wrong without more details but deadlock is (obviously) caused by multiple threads trying to acquire resources held by others. That really means that you must have at least two mutexes and two threads. Could that be happening in your code?

Thread.join doesn't have anything to do with parallel executiion - it's a synchronization method to enable one (usually the master) thread to wait for one or more threads to complete.

Answer 3

Which Ruby 1.9 implementation are you using? YARV cannot run Ruby Threads in parallel. At the moment, there is no production-ready implementation of Ruby 1.9 which can run threads in parallel. JRuby can threads in parallel, but its Ruby 1.9 implementation is not quite complete yet. (Although it is stable, so if all the features you need are there, you can use it.)