From: Kirk Haines <khaines@...>
Date: 2005-04-10T05:14:40+09:00
Subject: Re: My threading concern.

Aaron  Rustad wrote:

> When two theads enter a method that can change a value of an instance
> variable, does the possiblity exist that one thread's changes will
> clobber the other's?
> 
> The reason stems from the ApplicationController of Rails, when a
> request is received, the request is handled by a method that has access
> to instance variables (session, request, params). Coming from the
> Java/Struts world, this is a concern, and methods should not access
> instance variables.
> 
> Is there a different model of theading in Ruby, or, would I be missing
> something in Rails.

Threading is no different in Ruby than it is in other languages, with regard
to guarding against concurrent access.

If there is a section of code that should only be accessed in a serial
fashion, control that access with a Mutex:

m = Mutex.new
m.synchronize do
  @foo.update
  @bar.count += 1
end

Ruby provides a rich set of support beyond mutexes for dealing with
threading issues, should you need them.


Kirk Haines