From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-07-30T00:24:15+09:00
Subject: Re: Allow retry to take arguments?

On Fri, 29 Jul 2005, Austin Ziegler wrote:

> It's a neat idea, though, and I think that it could be generally
> useful, not just database useful.

i use these in my personal lib (http://codeforpeople.com/lib/ruby/alib/):

     #
     # initiates a catch block to do 'something'.  if the method try_again! is
     # called the block is done over - if the method give_up! is called the block
     # is aborted.  calls to attempt may be nested.
     #
       def attempt label = 'attempt'
         ret = nil
         n_attempts = 0
         loop{ break unless catch("#{ label }"){ ret = yield(n_attempts += 1) } == 'try_again' }
         ret
       end
     #
     # see attempt
     #
       def try_again! label = 'attempt'
         throw "#{ label }", 'try_again'
       end
     #
     # see attempt
     #
       def give_up! label = 'attempt'
         throw "#{ label }", 'give_up'
       end

usage like

   attempt do |n_attempts|
     begin
       db = connect
     rescue
       sleep 2 and try_again! if n_attempts < 3
     end
   end

and can be nested like

   attempt('connect') do |connect_attempts|
     begin
       db = connect

       attempt('transaction') do |transaction_attempts|
         begin
           db.execute sql
         rescue => e
           case e
             when ConnectionError
               sleep 2 and try_again!('connect') if connection_attempts < 3
             when TransactionError
               sleep 3 and try_again!('transaction') if transaction_attempts < 4
             else
               raise
           end
         end
       end

     rescue
       sleep 2 and try_again!('connect') if connection_attempts < 3
     end
   end


and end up using it alot for network type code.

-a
-- 
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| My religion is very simple.  My religion is kindness.
| --Tenzin Gyatso
===============================================================================