Problem with exception not beeing caught

ruby-talk
1

Dear rubyists!

I have a problem with a small programm, that's fetching emails from my
account and then goes to sleep for X seconds.
The code looks somehow like this:

loop do
  begin
    load FILTERFILE
    BOXES.each{|box| check_mailbox(box)}
    $log.debug("Gehe für #{SLEEPTIME} Sekunden schlafen!")
    sleep(SLEEPTIME)
  rescue
    $log.warn("Fehler aufgetreten:#{$!}\n#{$!.backtrace}")
  end
end

From time to time I get an exception in check_mailbox because the mailserver
doesn't respond so I'm gettin:
mi@ceres:~$ mail-forward.rb -n
/usr/local/lib/ruby/1.8/timeout.rb:42:in `new': execution expired
(Timeout::Error)
        from /usr/local/lib/ruby/1.8/net/protocol.rb:83:in `connect'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:82:in `timeout'
        from /usr/local/lib/ruby/1.8/timeout.rb:55:in `timeout'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:82:in `connect'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:64:in `initialize'
        from /usr/local/lib/ruby/1.8/net/pop.rb:427:in `open'
        from /usr/local/lib/ruby/1.8/net/pop.rb:427:in `do_start'
        from /usr/local/lib/ruby/1.8/net/pop.rb:415:in `start'
        from /home/mi/bin/mail-forward.rb:45:in `check_mailbox'
        from /home/mi/bin/mail-forward.rb:89
        from /home/mi/bin/mail-forward.rb:89:in `each'
        from /home/mi/bin/mail-forward.rb:89
        from /home/mi/bin/mail-forward.rb:86:in `loop'
        from /home/mi/bin/mail-forward.rb:86

I guess that's kinda normal, but: Why isn't this exception caught??? I
expected the exception in my logfile and the program to continue, but
obviously the program exits before getting into the rescue block??

Any ideas what i'm doing wrong?

Michael

2

When you don't specify an exception class to rescue from, it defaults to StandardError. Timeout::Error doesn't inherit from StandardError, so it goes uncaught:

   # show the ancestors: no StandardError!
   Timeout::Error.ancestors
     ==>[Timeout::Error, Interrupt, SignalException, Exception, Object, Kernel]

   # test rescuing the lowest exception class possible: Exception.
   begin
     raise Timeout::Error
   rescue Exception
     p 'rescued!'
   end
   "rescued!"
     ==>nil

   # test an unspecified exception class:
   begin
     raise Timeout::Error
   rescue
     p 'rescued!'
   end
   (irb):9:in `irb_binding': Timeout::Error (Timeout::Error)
         from /usr/local/lib/ruby/1.9/irb/workspace.rb:52:in `irb_binding'
         from /usr/local/lib/ruby/1.9/irb/workspace.rb:52

In fact, this made IRB die off on me; IRB didn't catch the error either.

HTH,
Mark

···

On Aug 9, 2004, at 12:16 AM, Michael Mueller wrote:

Dear rubyists!

I have a problem with a small programm, that's fetching emails from my
account and then goes to sleep for X seconds.
The code looks somehow like this:

loop do
  begin
    load FILTERFILE
    BOXES.each{|box| check_mailbox(box)}
    $log.debug("Gehe für #{SLEEPTIME} Sekunden schlafen!")
    sleep(SLEEPTIME)
  rescue
    $log.warn("Fehler aufgetreten:#{$!}\n#{$!.backtrace}")
  end
end

From time to time I get an exception in check_mailbox because the mailserver
doesn't respond so I'm gettin:
mi@ceres:~$ mail-forward.rb -n
/usr/local/lib/ruby/1.8/timeout.rb:42:in `new': execution expired
(Timeout::Error)
        from /usr/local/lib/ruby/1.8/net/protocol.rb:83:in `connect'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:82:in `timeout'
        from /usr/local/lib/ruby/1.8/timeout.rb:55:in `timeout'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:82:in `connect'
        from /usr/local/lib/ruby/1.8/net/protocol.rb:64:in `initialize'
        from /usr/local/lib/ruby/1.8/net/pop.rb:427:in `open'
        from /usr/local/lib/ruby/1.8/net/pop.rb:427:in `do_start'
        from /usr/local/lib/ruby/1.8/net/pop.rb:415:in `start'
        from /home/mi/bin/mail-forward.rb:45:in `check_mailbox'
        from /home/mi/bin/mail-forward.rb:89
        from /home/mi/bin/mail-forward.rb:89:in `each'
        from /home/mi/bin/mail-forward.rb:89
        from /home/mi/bin/mail-forward.rb:86:in `loop'
        from /home/mi/bin/mail-forward.rb:86

I guess that's kinda normal, but: Why isn't this exception caught??? I
expected the exception in my logfile and the program to continue, but
obviously the program exits before getting into the rescue block??

Any ideas what i'm doing wrong?

3

Hi Mark,

When you don't specify an exception class to rescue from, it defaults
to StandardError. Timeout::Error doesn't inherit from StandardError, so
it goes uncaught:

Ups! Didn't think about that possibility!
I changed the code the rescue Timeout::Error and now it works :slight_smile:

Thanks!

Michael