From: nobu.nokada@...
Date: 2002-05-10T07:59:23+09:00
Subject: Re: timeout.rb problem

Hi,

At Fri, 10 May 2002 06:56:16 +0900,
Nikodemus Siivola wrote:
> The scripts below prints out "achived enlightenment, exiting
> gracefully...", which is in this context quite understandable -- but
> extremely surprising if the inner timeout is "more distant", in a library
> module for example.

You can use particular exception classes.

> #!/usr/bin/ruby
> 
> require 'timeout'
> 
> def meditate
>   begin
      to = Class.new(TimeoutError)
      timeout(10, to) { loop { self.inspect } }
    rescue to
>     puts "achived enlightenment, exiting gracefully..."
>     exit
>   end
> end
> 
> def try_to_meditate
>   begin
      to = Class.new(TimeoutError)
      timeout(1, to) { meditate }
    rescue to
>     puts "meditation takes too long, rush to abort!"
>     abort
>   end
> end
> 
> try_to_meditate
> 
> __END__

>  - Is this technically correct? Should a rescue block rescue
>    an exception that is raised from outside of it's scope?

Yes, that's exception.

>  - Is this really the way timeout's should behave? Maybe TimeoutError
>    could contain information of it's nesting level so that when
>    rescuing a timeout one could reraise it so that the higher level
>    code would have a chance to rescue it too...

Like this?


Index: timeout.rb
===================================================================
RCS file: /cvs/ruby/src/ruby/lib/timeout.rb,v
retrieving revision 1.10
diff -u -2 -p -r1.10 timeout.rb
--- timeout.rb	2002/01/16 03:36:32	1.10
+++ timeout.rb	2002/05/09 22:53:52
@@ -27,8 +27,11 @@
 
 class TimeoutError<Interrupt
+  class NestedInternal<Interrupt
+  end
 end
 
-def timeout(sec, exception=TimeoutError)
+def timeout(sec, exc = nil)
   return yield if sec == nil
+  exception = exc || Class.new(TimeoutError::NestedInternal)
   begin
     x = Thread.current
@@ -39,4 +42,7 @@ def timeout(sec, exception=TimeoutError)
     yield sec
 #    return true
+  rescue exception => e
+    raise if exc
+    raise TimeoutError, e.message, e.backtrace
   ensure
     y.kill if y and y.alive?


-- 
Nobu Nakada