ExceptionManager

Gem for better exception recording.

Installation

Add this line to your application's Gemfile:

gem 'exception_manager'

And then execute:

$ bundle

Or install it yourself as:

$ gem install exception_manager

Usage

First of all, make sure that ExceptionManager is enabled in your application.

# config/initializers/exception_manager.rb
ExceptionManager.enable!

That's it! Now you can use it.

class TestClassThatRaisesException
  @@class_variable = :class_value

  def test_error(*args)
    @instance_variable = :instance_value

    raise 'Test error'
  end
end

begin
  TestClassThatRaisesException.new.test_error(1, 2, 3)
rescue => e
  puts "Subject: #{e.subject}"
  puts "Locals: #{e.locals}"
  puts "Instance variables: #{e.subject_instance_variables}"
  puts "Class variables: #{e.subject_class_variables}"
  puts "Summary: #{e.summary.inspect}"
end

And if you have pry, you can combine it:

e._binding.pry

Integration with monitoring systems like NewRelic

NewRelic uses to_s method for fetching message from exception: source.

Unfortunately you cannot override to_s method like this:

# DO NOT ADD THIS CODE TO YOUR PROJECT
# IF YOU DON'T WANT TO GET SEGFAULT
class YourApiBaseException < StandardError
  def to_s
    [super, summary.inspect].join(' ')
  end
end

The solution is in this line: source

Instead of overriding to_s method we can override original_exception method:

# This code is safe
class YourApiBaseException < StandardError
  def original_exception
    message_for_new_relic = [message, summary.inspect].join(' ')
    self.exception(message_for_new_relic)
  end
end

From this moment all exceptions inherited from YourApiBaseException will have message with exception summary:

begin
  raise YourApiBaseException, 'my custom message'
rescue YourApiBaseException => e
  puts e.original_exception.to_s # this is exactly what NewRelic gem calls
end
# => 'my custom message {:locals=>..., :subject=>..., }'

Other systems may use message method, so the code will look like:

class YourApiBaseException < StandardError
  def message
    [super, summary.inspect].join(' ')
  end
end

If you don't know exactly which method is used in your monitoring system, you can simply override both :smile:

Contributing

1. Fork it ( https://github.com/[my-github-username]/exception_manager/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request