Automatically Logging Exceptions in Ruby

Question

Is there a library or easy way to catch exceptions thrown in a Ruby program and log it to a file? I've looked over log4r and logger, but the docs on both don't provide any examples on how I would do this. I run this program remotely and lose handles to stdout and stderr, if that information helps at all.

What would you recommend?

Answer 1

Rescue from Exception. Something like this probably makes sense:

begin
  # run your code here ..
rescue Exception => exception
  # logger.error(...) ....
  raise exception
end

This will log the exception, and re-raise it so that the application actually raises an error in addition to the logging.

exception is an instance of Exception, take a look at the docs for information about what you can do with this object (such as accessing the backtrace).

Answer 2

If you want to take a walk on the wild side, try this:

class Exception
    alias real_init initialize
    def initialize(*args)
        real_init *args
        # log the error (self) or its args here
        end
    end

What this does is intercept the creation of new exception objects at the moment of creation.

Answer 3

If you're running a Rails app, the Exception Notification plugin is very handy.

Answer 4

Would it work if I did something like this:

begin
  main()
rescue Exception => e
  myCustomErrorLogger(e)
end

def main()
  # All the application code comes here.
end

What I need is to have all my uncaught exceptions move to the top-most level, and be caught there and subsequently recorded by the error logging function.

I'm trying this out now, but it would be great to have your suggestions.