= Exception Notifier Plugin for Rails
The Exception Notifier plugin provides a mailer object and a default set of
templates for sending email notifications when errors occur in a Rails
application. The plugin is configurable, allowing programmers to specify:
* the sender address of the email
* the recipient addresses
* the text used to prefix the subject line
The email includes information about the current request, session, and
environment, and also gives a backtrace of the exception.
== Usage
First, include the ExceptionNotifiable mixin in whichever controller you want
to generate error emails (typically ApplicationController):
  class ApplicationController < ActionController::Base
    include ExceptionNotifiable
    ...
  end
Then, specify the email recipients in your environment:
  ExceptionNotifier.exception_recipients = %w(joe@schmoe.com bill@schmoe.com)
And that's it! The defaults take care of the rest.
== Configuration
You can tweak other values to your liking, as well. In your environment file,
just set any or all of the following values:
  # defaults to exception.notifier@default.com
  ExceptionNotifier.sender_address =
    %("Application Error" <app.error@myapp.com>)
  # defaults to "[ERROR] "
  ExceptionNotifier.email_prefix = "[APP] "
Email notifications will only occur when the IP address is determined not to
be local. You can specify certain addresses to always be local so that you'll
get a detailed error instead of the generic error page. You do this in your
controller (or even per-controller):
  consider_local "64.72.18.143", "14.17.21.25"
You can specify subnet masks as well, so that all matching addresses are
considered local:
  consider_local "64.72.18.143/24"
The address "127.0.0.1" is always considered local. If you want to completely
reset the list of all addresses (for instance, if you wanted "127.0.0.1" to
NOT be considered local), you can simply do, somewhere in your controller:
  local_addresses.clear
== Customization
By default, the notification email includes four parts: request, session,
environment, and backtrace (in that order). You can customize how each of those
sections are rendered by placing a partial named for that part in your
app/views/exception_notifier directory (e.g., _session.rhtml). Each partial has
access to the following variables:
* @controller: the controller that caused the error
* @request: the current request object
* @exception: the exception that was raised
* @host: the name of the host that made the request
* @backtrace: a sanitized version of the exception's backtrace
* @rails_root: a sanitized version of RAILS_ROOT
* @data: a hash of optional data values that were passed to the notifier
* @sections: the array of sections to include in the email
You can reorder the sections, or exclude sections completely, by altering the
ExceptionNotifier.sections variable. You can even add new sections that
describe application-specific data--just add the section's name to the list
(whereever you'd like), and define the corresponding partial. Then, if your
new section requires information that isn't available by default, make sure
it is made available to the email using the exception_data macro:
  class ApplicationController < ActionController::Base
    ...
    protected
      exception_data :additional_data
      def additional_data
        { :document => @document,
          :person => @person }
      end
    ...
  end
In the above case, @document and @person would be made available to the email
renderer, allowing your new section(s) to access and display them. See the
existing sections defined by the plugin for examples of how to write your own.
== Advanced Customization
By default, the email notifier will only notify on critical errors. For
ActiveRecord::RecordNotFound and ActionController::UnknownAction, it will
simply render the contents of your public/404.html file. Other exceptions
will render public/500.html and will send the email notification. If you want
to use different rules for the notification, you will need to implement your
own rescue_action_in_public method. You can look at the default implementation
in ExceptionNotifiable for an example of how to go about that.
Copyright (c) 2005 Jamis Buck, released under the MIT license