From: John Carter <john.carter@...>
Date: 2008-10-07T12:08:14+09:00
Subject: Re: Ruby lacks atfork : The evil that lives in fork...

On Tue, 7 Oct 2008, Joel VanderWerf wrote:
> You can atfork in ruby; fsdb uses this kind of construct:
>
> module ForkSafely
>  def fork
>    # clean up before forking
>    super do
>      # clean up after forking, in child
>      # clean up inconsistent mutexes, etc.
>      yield
>    end
>    # clean up after forking, in parent
>  end
> end
>
> include ForkSafely

Hmm. Cute. Really cute.

Can I chain the at fork handlers?
Does it work for Process.fork as well?

Let me try...
======================================================================

module A

    def fork
       puts "Prereal"
       pid = super do
          puts "In real"
          yield
       end
       puts "post real"
       pid
    end

end
include A

pid = fork do
    puts "Did it work?"
end

Process.waitpid2 pid


module B
    def fork
       puts "Prereal1"
       pid = super do
          puts "In real1"
          yield
       end
       puts "post real1"
       pid
    end
end
include B

pid2 = fork do
    puts "Does chained work?"
end
Process.waitpid2 pid2

puts "Yes nested did work, does Process.fork work too?"

pid3 = Process.fork do
    puts "Does Process.fork work?"
end
Process.waitpid2 pid3

puts "No it didn't"

module C

    def Process.fork
       puts "b4 proc fork"
       super do
          puts "in proc fork"
          yield
       end
       puts "Post proc fork"
    end
end

include C

pid2 = Process.fork do
    puts "Bah"
end
======================================================================
ruby -w a.rb
Prereal
In real
Did it work?
post real
Prereal1
Prereal
In real
In real1
Does chained work?
post real
post real1
Yes nested did work, does Process.fork work too?
Does Process.fork work?
No it didn't
a.rb:52: warning: redefine fork
b4 proc fork
Prereal1
Prereal
In real
In real1
in proc fork
Bah
post real
post real1
Post proc fork
======================================================================
Hmm. Almost, but I can't get rid of this warning...
   a.rb:52: warning: redefine fork

any suggestions on how to get rid of that pesky warning?

John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand