From: Sylvain Viart <sylvain@...>
Date: 2008-09-30T01:22:52+09:00
Subject: exception in thread?

Hi,

I'm trying to use Net::SSH::Multi.  http://net-ssh.rubyforge.org/

It seems that ruby have difficulties to catch exception in multi 
threaded mode, any hint?

the doc said, if we put (:on_error => :warn) it shouldn't fail, be the 
exception begin/rescue bloc did catch the exception, here 
Errno::EHOSTUNREACH

/var/lib/gems/1.8/gems/net-ssh-multi-1.0.0/lib/net/ssh/./multi/session.rb
468     def next_session(server, force=false) #:nodoc:
[...]
482       begin
483         server.new_session
484       rescue Exception => e
485         server.fail!
486         @session_mutex.synchronize { @open_connections -= 1 }
487
488         case on_error
489         when :ignore then
490           # do nothing
491         when :warn then
492           warn("error connecting to #{server}: #{e.class} 
(#{e.message})")
493         when Proc then
494           go = catch(:go) { on_error.call(server); nil }
495           case go
496           when nil, :ignore then # nothing
497           when :retry then retry
498           when :raise then raise
499           else warn "unknown 'go' command: #{go.inspect}"
500           end
501         else
502           raise
503         end
504
505         return nil
506       end
[...]


As we can test, we are able to catch the exception at to level, could 
you confirm its tread related?

require 'rubygems'
require 'net/ssh/multi'
Net::SSH::Multi.start(:on_error => :warn) do |session|
  # define the servers we want to use
  session.use 'root@server-04'
  session.use 'root@server-07'  # doesn't exist
  session.use 'root@server-08'

  # execute commands on all servers
 begin
    session.exec( "hostname" )
 rescue Exception => e
    p "main:#{e}"
 end

  # run the aggregated event loop
  session.loop
end

ruby 1.8.5 (2006-08-25) [x86_64-linux]

Regards,
Sylvain.