ar_mailer¶ ↑

A two-phase delivery agent for ActionMailer

Rubyforge Project:

rubyforge.org/projects/seattlerb

Documentation:

seattlerb.org/ar_mailer

and for forked additions

github.com/adzap/ar_mailer/wikis

Bugs:

adzap.lighthouseapp.com/projects/26997-ar_mailer

Even delivering email to the local machine may take too long when you have to send hundreds of messages. ar_mailer allows you to store messages into the database for later delivery by a separate process, ar_sendmail.

Before installing you will need to make sure the original gem is uninstalled as they can’t coexist:

$ sudo gem uninstall ar_mailer

Then

$ sudo gem install adzap-ar_mailer

For Rails >= 2.1, in your environment.rb:

config.gem "adzap-ar_mailer", :lib => 'action_mailer/ar_mailer'

# or since version 2.1.7 of this gem you can now just do

config.gem "adzap-ar_mailer"

For Rails 2.0, in an initializer file:

require 'action_mailer/ar_mailer'

Go to your Rails project:

$ cd your_rails_project

Create the migration and model:

This shows the options which are only the model name, which defaults to Email

./script/generate ar_mailer -h

Then run with defaults

./script/generate ar_mailer

Or specify a custom model name

./script/generate ar_mailer Newsletter

See Alternate Mail Storage if you use a custom model name

In your mailer class methods you must be sure to set the From address for your emails. Something like:

def list_send(recipient)
  from 'no_reply@example.com'
  # ...

Edit config/environments/production.rb and set the delivery method:

config.action_mailer.delivery_method = :activerecord

Or if you need to, you can set each mailer class delivery method individually:

class MyMailer < ActionMailer::Base
  self.delivery_method = :activerecord
end

This can be useful when using plugins like ExceptionNotification. Where it might be foolish to tie the sending of the email alert to the database when the database might be causing the exception being raised. In this instance you could override ExceptionNofitier delivery method to be smtp or set the other mailer classes to use ARMailer explicitly.

Then to run it:

$ ar_sendmail

You can also run it from cron with -o, or as a daemon with -d.

See ar_sendmail -h for full details.

By default ar_mailer assumes you are using an ActiveRecord model called Email to store the emails created before sending. If you want to change this you alter it in an intializer like so:

ActionMailer::Base.email_class = Newsletter

If you are using Ruby >= 1.8.7, TLS will be enabled automatically if your SMTP server supports it. If you do not want it to automatically enabled then set the :tls option to false in your smtp_settings.

If you are on Ruby <= 1.8.6, then the TLS patch included in this plugin will be loaded, so you don’t need another TLS plugin to add the capability. This patch allows you to explicit set if the server supports TLS by setting the :tls option to true in your smtp_settings.

The biggest downside to using ar_mailer is that it loads the entire Rails app into memory. For larger apps this can be just a whole lot of wasted memory given all you need is to access the email table and mailer settings. We can get around this using a few conventions and save around 50% or more of the memory used when loading the full app.

Loading the database is not much of a problem since the config sits in its own yaml which is easy to load in isolation from the app. The mailer settings are trickier since they are usually in the environment file which depends on loading the Railties system and therefore the whole app.

To workaround for this we need to put all the SMTP settings in a yaml config file like the database settings. Like so

in config/email.yml

development:
  domain: example.com
  address: smtp.example.com
  port: 25

production:
  domain: example.com
  address: smtp.example.com
  port: 25

You can still have ActionMailer settings in each environment file but just be sure they don’t override these SMTP settings. The other settings aren’t needed when running ar_sendmail since they only apply to the generation of an email which has already happened inside the running application.

To avoid duplication of these settings you need to have an initializer which will will read the same config file and load these settings. This is in case you switch back the normal environment loading. Keeping the email settings here is good idea, since just the like the database, they are external connection settings being stored in the config folder.

The initializer in config/initializers/action_mailer.rb:

config_file = "#{Rails.root}/config/email.yml"
mailer_options = YAML::load(ERB.new(IO.read(config_file)).result)
if mailer_options[Rails.env]
  ActionMailer::Base.smtp_settings = mailer_options[Rails.env].symbolize_keys
end

At the moment if you are using a database driver that doesn’t come with Rails, the gem will need to be installed on the target system.

Now to run ar_sendmail with minimal environment we do:

ar_sendmail -e production -c /path/to/app --minimal

If you have any troubles or find any bad assumptions in the minimal set up let me know.

See ar_sendmail -h for options to ar_sendmail.

NOTE: You may need to delete an smtp_tls.rb file if you have one lying around. ar_mailer supplies it own.

For Linux both script and demo config files are in share/linux. See ar_sendmail.conf for setting up your config. Copy the ar_sendmail file to /etc/init.d/ and make it executable. Then for Debian based distros run ‘sudo update-rc.d ar_sendmail defaults’ and it should work. Make sure you have the config file /etc/ar_sendmail.conf in place before starting.

For FreeBSD or NetBSD script is share/bsd/ar_sendmail. This is old and does not support the config file unless someone wants to submit a patch.