Exception notifier plugin causing internal server error

I am using the exception notifier plugin to send me emails on the details of all unhandled exceptions in my web app (read about this plugin on my earlier blog posting, Exception notification plugin).  I recently put my web app on a new server, and when an unhandled exception occurred, Internal Server Error was displayed to the user, and no email was sent.  After digging in to this, I found that the exception notification code itself was generating an exception.  The offending file is views/exception_notification/_environment.rhtml.  Turns out there is a syntax error in that file when using Ruby 1.8.6 patch level 110 or higher.  The plugin was fixed in November 2007, but I had downloaded the plugin before that time.  

The fix is described at http://dev.rubyonrails.org/ticket/9940.  Simply edit the plugsin/exception_notification/views/exception_notification/_environment.rhtml file, and change the third line to:

* <%= "%-*s: %s" % [max.length, key, filter_sensitive_post_data_from_env(key, @request.env[key].to_s.strip)] %>

The only difference is that the first *- is changed to -*.

Exception_notification plugin for automated exception emailing

I found a really useful plugin called exception_notification that I've been using on my servers for several months now. It will send emails to addresses that you configure any time an exception is generated on your server, if the server is in production mode. The email contains the full details of the exception, including the call stack. It's almost as useful as the error page that gets displayed for exceptions in development mode.

The plugin has helped me discover and fix a whole bunch of obscure errors that I never would have discovered on my own or through users complaining.

This may not be appropriate for a server where you have a large volume of users. You probably wouldn't want to get thousands of emails of the exact same error a day especially if it's a bug that you already know about. But it works great for servers with a low volume of users, or for internal test servers. For a test server, your testers won't need to record the details of the error and send it to you separately, it will automatically be sent to you!

To get started, run

script/plugin install exception_notification

Then edit your config/environment.rb file to include the following line, specifying the email addresses to send exceptions to:

ExceptionNotifier.exception_recipients = %w(email_recipient_1@address.com email_recipient_2@address.com)

Another useful option you can add to environment.rb specifies who the sender of the exception should appear as:

ExceptionNotifier.sender_address = "\"App Error\" <apperror@domain.com>"

Then add this to your application controller if you want all actions in your application to generate exception emails.

class ApplicationController < ActionController::Base
include ExceptionNotifiable 

You can also include this only on the controllers that you want to generate exception emails.

The full source for this is at http://dev.rubyonrails.org/browser/plugins/exception_notification. Read the README file there for more detailed information on configuring it.