Thread safety

Ruby
1

With the discussion surrounding merb/rails and thread safety, I’ve been
somewhat concerned with making my own tiny home-rolled web apps that I
write thread safe, if only to become more knowledgeable on the subject.

I know it’s probably hard to generalize, but does anybody have any
simple rules to follow (or resources to share) for writing thread safe
code?

Thanks!

2

On Feb 15, 2008, at 10:54 AM, Jeff Turc wrote:

Thanks!
Anyone else jump right in here. These are mine:

Rule #1: Don’t use global variables.
Rule #2: If you do, when you change them, wrap them in a blocking
mechanism such as a mutex or critical section so two threads can’t try
at once.
Rule #3: If you are changing the state of an object that is not thread-
local, wrap the change in a mutex (etc.)

So, for example:

require ‘thread’
my_object_sync = Mutex.new

Thread.new do

just lock on this object

my_object_sync.synchronize do
# Update that is not atomic
end
end

Rule #4: Don’t be too sure that any operation in Ruby is atomic.

3

On 15.02.2008 21:08, s.ross wrote:

On Feb 15, 2008, at 10:54 AM, Jeff Turc wrote:

I know it’s probably hard to generalize, but does anybody have any
simple rules to follow (or resources to share) for writing thread safe
code?

Rule #3: If you are changing the state of an object that is not thread-
local, wrap the change in a mutex (etc.)

Corollary: use thread confinement, i.e. design your app in a way that
most objects are used in a single thread at a time only. Restrict need
for synchronization to the minimum needed.

Rule #4: Don’t be too sure that any operation in Ruby is atomic.

Somehow this reminds me of “Blondie” and “Atomic”. :slight_smile: Those were the
days…

Cheers

robert

4

Somehow this reminds me of “Blondie” and “Atomic”. :slight_smile: Those were
the days…

One way or another :slight_smile:

5

Steve R. wrote:

Somehow this reminds me of “Blondie” and “Atomic”. :slight_smile: Those were
the days…

One way or another :slight_smile:

I’m gonna getcha!

Thanks guys. big help.

6

For anyone else starting out with threads, I also stumbled across this:

8 Simple Rules for Designing Threaded Applications
http://www.devx.com/go-parallel/Article/37034

7

On Mon, 2008-02-18 at 06:55 +0900, Jeff Turc wrote:

For anyone else starting out with threads, I also stumbled across this:

8 Simple Rules for Designing Threaded Applications
http://www.devx.com/go-parallel/Article/37034

I think this is a good article and I wouldn’t mind recommending it to
others.

Thanks Jeff!

-mental