Global Error Catching

To handle errors globally in your application, add..

(within application.rb) def rescueactionin_public(exception) render :text => "

There was a global error processing your request.

" end def local_request? false end

The final def def local_request? tells rails that it should act the same way in development mode.

Local Error Catching

To catch errors locally within your form submits do...

def update return unless request.post? begin User.update(self.current_user.id, params[:user]) render :action => 'success' rescue ActiveRecord::RecordInvalid flash[:notice] = "Sorry, your profile was not saved" render :action => 'profile'
rescue flash[:notice] = "Sorry, something went wrong" render :action => 'profile' end end

Simple process, here we're basically saying if the user has submitted form data (done a POST), then process the code; if not redirect back to the sending page.

If yes then update the User object relevant to the specific user record (found by the id), updating the record with the parameters from the form. Save the record and render the 'success' page.

If we get a problem with saving the record (activerecord), display a message and goto the 'profile' page.

If we get some other error, display the second message and goto the 'profile' page.

Notify Me of Errors via Email

On top of this you can enhance it with flash messages and send off an email with the error code, here's one such way.

(in application.rb) protected

def log_error(exception) super(exception)

begin
    Alert.deliver_errormail(
      exception, 
      clean_backtrace(exception), 
      @session.instance_variable_get("@data"), 
      @params, 
      @request.env)
rescue => e
    logger.error(e)
end

end

Adding this makes it send error emails in development mode..

def local_request? false end

Now create an Mailer object with...

script/generate mailer Alert

And put this code in your generated alert.rb file

class Alert < ActionMailer::Base def errormail(exception, trace, session, params, env, sent_on = Time.now) content_type "text/html" @recipients = 'john@gmail.com' @from = 'admin@mysite.com' @subject = "[Error] exception in #{env['REQUEST_URI']}" @senton = senton @body["exception"] = exception @body["trace"] = trace @body["session"] = session @body["params"] = params @body["env"] = env end end

And create a appropriate alert/errormail.rhtml file in your view for the formatted error email...

Error report from <%= Time.now %>

<% if @session['user'] -%> <% end -%>

Message	<%= @exception.message %>
Location	<%= @env['REQUEST_URI'] %>
Action	<%= @params.delete('action') %>
Controller	<%= @params.delete('controller') %>
Query	<%= @env['QUERY_STRING'] %>
Method	<%= @env['REQUEST_METHOD'] %>
SSL	<%= @env['SERVER_PORT'].to_i == 443 ? "true" : "false" %>
Agent	<%= @env['HTTP_USER_AGENT'] %>
User id	<%= @session['user'].id %>
User name	<%= @session['user'].name %>
User email	<%= @session['user'].email %>
Registered	<%= @session['user'].created_at %>

Backtrace

Params

---

<% for key, val in @params -%>

<%= key %>

<%= val.to_yaml.to_a.join("

\n

") %>

<% end if @params -%>

Session

---

<% for key, val in @session -%>

<%= key %>

<%= val.to_yaml.to_a.join("

\n

") %>

<% end if @session -%>

Environment

---

<% for key, val in @env -%> <% end if @env -%>

<%= key %>

<%= val %>

Now whenever an error happens you'll get an email about it, good for the production environment.

Setup the Emailer

Remember to setup the emailer otherwise no emails will be sent.

By adding this to your environments/production.rb

config.actionmailer.raisedelivery_errors = true ActionMailer::Base.delivery_method = :sendmail ActionMailer::Base.sendmail_settings = { :location => '/usr/sbin/sendmail', :arguments => '-i -t' }

Or more detailed,

• my rails email tutorial

Setup a DNS MX Record so you don't get blacklisted!

A further note, remember to add an MX record for the domain your using otherwise your site will be blacklisted by anti-spam sites.

An MX record basically tells other sites where they should send emails to, it's like saying where the postman should deliver incoming letters.

Now if your only sending emails you shouldn't need this but as a previous commenter noted, most anti-spam sites blacklist you if your sending and don't have one; regardless of whether you want the site to receive emails or not. Hence you've got to include one.

A simple example is...

type: MX name: mysite.com data: ASPMX.L.GOOGLE.COM. auxilary info: 1

Now ok, this is actually telling anti-spammers your using Google Applications to handle your email (which isn't strictly true) but at least it get's them off your back until you setup your own full-blown POSTFIX mail server.

Which is something I'm working on writing an article for.

Expect that in a future posting.