Rails - Jan 2008 - Exception Handling Approach - This is what I'm doing...

Hi - Any feedback from people re how they handle exception handling in
RoR?   Here''s what I''m doing...


I''ve ended up doing the following so far, some of which are adjustments
to
Jamis Buck''some "Exception Notification" plugin. 
I''m still optimizing this
for my own usage as I go.  Hope this helps (any ideas/feedback welcome):

Usage:
if error_situation_occurs
  raise Error.new( "Message to User Here - Will be shown on error
page",
                   "Additional message that will go to log file for
developers",
                    Logger::ERROR)
end

Features:
* Separate user & developer messages
* Do not have to catch such errors back in controller or views as the
below-mentioned rails rescue frame work will handle ( i.e. less work,
cleaner code)
* Just need to raise the Error exception which then triggers/implies/carries
out:
  (a) appropriate email message to user
  (b) developer specific additional message to logs
  (c) severity of log entry raised
  (b) triggers Email/SMS alert based on severity of the error (use of Ruby
Logger severity levels)


-----------------------------------
class Error < RuntimeError
  attr :developer_message
  attr :severity

  def initialize(user, dev=nil, sev=Logger::FATAL)
    super user                          # Use normal exception parameter for
User Message
    @developer_message = dev || user    # Set developer focused message
    @severity = sev
  end
end
-----------------------------------
def rescue_action_in_public(exception)    # Override this Rails method
  case exception
    when *exceptions_to_treat_as_404
      render_404
    else
      if exception.instance_of?(Error)   # Added by Greg
        # Custom Error (caught)
        render_custom_error
        case (exception.severity)
        when Logger::FATAL
          # trigger an email/sms for FATALs
          send_notification(exception)
        else
          # no emails/sms otherwise - future step: have this configurable in
environment.rb
        end
      else
        # 500 Error (not caught)
        render_500
        send_notification(exception)
      end
  end
end
--------------------------------
def render_custom_error
  respond_to do |type|
    type.html { render :template => "error/custom_500_error"}
    type.all  { render :nothing => true, :status => "500 Error"
}
  end
end
---------------------------------
def log_error(exception) #:doc:           # Override this Rails method
  ActiveSupport:: Deprecation.silence do
    if ActionView::TemplateError === exception
      logger.fatal(exception.to_s)
    else
      if exception.instance_of?(Error)    # Added by Greg - logs the User
Message, Log/Developer Message and limits stack trace to first 3 lines
        # Custom Error (caught)
        logger.error("#{exception.developer_message}\n" +
          "  Exception Class:#{exception.class}\n" +
          "  User Msg: #{exception.message }\n" +
          "  Backtrace:\n  " +
clean_backtrace(exception)[0..2].join("\n
") + "\n\n"
        )
      else
        logger.fatal("#{exception.developer_message }\n" +
          "  Exception Class:#{exception.class}\n" +
          "  Backtrace:\n  " +
clean_backtrace(exception)[0..2].join("\n
") + "\n\n"
        )
      end
    end
  end
end

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class SomethingsController < ApplicationController
def create
@something = Something.create!(params[:something])
flash[:success] = "Something was created!"
rescue ActiveRecord::RecordNotSaved, ActiveRecord::RecordInvalid
flash[:errors] = "Something could not be created."
render :action => "new"
end
end

You did say any feedback.

This is currently what we''re doing and hopefully later on when other
exceptions are raised we will be notified by email.

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