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([email protected] [email protected])

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 [email protected]
ExceptionNotifier.sender_address =
  %("Application Error" <[email protected]>)

# 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.