Maintenance and Monitoring Checklist for your Ruby on Rails Application

Before your application goes into production there are some maintenance and monitoring tasks you need to consider. These tasks include:

1. Backups
2. Log Rotation
3. Monitoring
4. Scheduled Jobs

Backups

You need to maintain offsite backups for your application’s:

• database,
• shared assets, and
• source code repository.

I have a set of backup scripts (executed via a nightly cron process) that dumps the database for each of my applications, which are in turn archived, and then downloaded to my server. Shared assets, those files uploaded via your application typically located in the public folder, are synced to my server and then archived. As my source control is hosted on Github, I don’t need to worry about backing this up.

Log Rotation

Installing the logrotate package will take care of your system logs, but you will need to set up log rotation specifically for your Rails application. I typically deploy my applications using Moonshine, a server provisioning tool from the folks at Rails Machine, so log rotation has been addressed. There maybe some other logs that are generated by your application such as Ferret server. Consider these files in your applications log folder:

• production.log
• mongrel.log (not necessary if you deploy on Passenger of course)
• ferret.log (other log producing components)

Monitoring

Monitoring is split into four categories:

• Monitoring Services
• Performance Monitoring
• External Monitoring
• Exception Notification

Monitoring services such as Apache, MySQL or even processes that are apart of your application, such as the Ferret server can be monitored by Monit or God. If these services go down unexpected, they are automatically restarted by the monitor.

Performance Monitoring can be broken down further into Server and Application Performance. Munin is a good candidate for the first, while service providers such as New Relic and Scout are good for the later. With Server monitoring you will also want to consider the consumption of resources. For example, how much disk space do I have left? How much RAM do I have left?

An external monitoring service is useful. Services such as Monstatic, 24×7, or Pingdom can notify you when your server is inaccessible.

Finally, the Exception Notification plugin suits my needs to be notified of an exception, but you may prefer a service to manage this such as Airbrake Bug Tracker or Exceptional.

Cron Jobs (Schedule Jobs)

Sometimes you will need to run scheduled jobs against your application such as managing recurring subscriptions. Make sure these are installed and running. It’s best to make these a part of your deployment using whenever or again, my preference is using Moonshine.

If you are you are using ActiveRecord-based sessions in your application, then you will definitely need to setup a task to remove old records in the sessions table.

Designing Dwayne Brown Studio: Focus your website on key customer tasks

Summary: Focusing your website on key customer tasks maximizes your budget and lead generation.

I position myself as a Ruby on Rails developer in Montreal for database web applications. However, I often have to put on other hats for a project, depending on the budget and the team members involved. In the case of Dwayne Brown Studio, I was responsible for not only the programming of web pages and custom content management system, but I was also responsible for the visual design, interaction, and architecture of the site.

When defining the architecture of a website, I use a customer-centered design approach. A customer persona, a fictional representation of the target audience for your website, is defined. In this case, it was Helen Brightman, a communications manager for a private school in Ottawa. The key task for Helen is to navigate the portfolio to identify photos related to education.

Online photography portfolios are often poorly designed. They suffer from overly “creative” navigation tools, small or abstract thumbnails, and no captions, making it difficult for people like Helen to identify relevant imagery. Even Dwayne’s previous website suffered from some of these issues.

Using an agile development technique know as Do The Simplest Thing That Could Possibly Work, I focused my efforts on creating a simple portfolio that was easy to navigate.

Three guiding objectives were used in designing the portfolio:

1. Help Helen identify relevant imagery
2. Allow Helen to scan photos quickly
3. Reduce pogosticking—jumping back from thumbnails to detail pages

This resulted in the following designs:

Dividing the portfolio into sections where related photos are grouped together, allows Helen to easily identify relevant imagery:

Large thumbnails on a scrolling page allows Helen to scan photos quickly:

A navigation control allows Helen to navigate through photos without having to return to the thumbnails page:

By identifying the key tasks of your customer, you can focus the web design process on what really matters and avoid “creative” solutions that just don’t work for your target audience.

Use Stubs and Expectations to Simplify Testing with Named Scopes

Summary: Use stubs to return the original class for a named scope, and use expectations to specify scope requirements to simplify testing

Testing with chained named scopes that have complex attributes such as conditions can be tricky. I try to combine named scopes with clear names to communicate intent, rather than have long chains floating around in code. This can be done simply by creating a plain old method, with scoped procedures or this hack. This is a good way to keep named scopes DRY when using a specific combination across your application code. Of course you should test your named scopes.

However, consider the situation when adding a simple extension to your named scope that doesn't warrant a new named scope or combination. As an example I have the following code in a catalog application:

class Catalog
  ...
  # Returns a set of ordered page numbers based on the product page numbers
  def page_numbers
    Product.printable.find(:all, :select => "DISTINCT products.page_number").
      collect {|product| product.page_number}
  end
  ...
end

The printable named scope is quite complex and has been tested. I wanted to avoid duplicating test data (although factories would help here). For this method I was only concerned about a collection of products and it's page numbers, not that fact it was scoped. But it is a requirement that the products are scoped to only those that are printable.

Stubbing and setting expectations help us simplify the test and express the requirement. By stubbing the named scope and returning the Product class we can focus on creating test data for which we are concerned -- products with page numbers. The expectation "find printable products", ensures that we have scoped products as required.

class CatalogTest < ActiveSupport::TestCase

  context "with page numbers" do

    setup do
      Product.stubs(:printable).returns(Product)      
    end

    context "generally" do
      setup do
         Catalog.page_numbers
      end

      before_should "find printable products" do
        Product.expects(:printable).returns(Product)
      end      
    end

    context "when no products" do
      should "return an empty array" do
        assert_equal [], Catalog.page_numbers
      end
    end

    context "when multiple products" do
      setup do
        Factory(:catalog_with_page_numbers)
      end

      should "return an array of page numbers" do
         assert_equal [0, 1, 2, 3], Catalog.page_numbers
      end     
    end
  end
end

Although setting this expectation increases coupling to the implementation, we are justified in that it expresses the requirement in the test example.

Combining Named Scopes

This is a useful way to combine named scopes:

# add to lib/named_scopes.rb for example
class ActiveRecord::Base
  def self.named_scopes(name, &block)
    metaclass.send(:define_method, name) {|*args| block.call(*args) }
  end
end 

Usage:

class Product
  named_scope :live, :conditions => {:active => true}
  named_scope :created_recently, :conditions => [created_at > ?", Time.now - 10.days]
  named_scopes(:recently_released) { live.created_recently  }   
end

Source: http://august.lilleaas.net/combining_named_scopes (no longer available)

Ask for help: background-image disappears on Internet Explorer 7 when in a div with float

I came across a strange CSS bug with IE 7 today. When I have a container that is floating and I use a text replacement technique the image does not show. Remove the float and it does. Or alternatively remove the DocType and it also works.

Browsing the 'net I haven't managed to find this bug. Have you come across this before? Do you have an explanation?

Personas: rich insight developed through research and making it an actionable design and decision-making tool

A great quote I discovered regarding the purpose of personas in the comments on a post titled Putting personas under the microscope in The Cooper Journal: It's important to remember that personas aren't an end in themselves, but a way of taking all that rich insight developed through research and making it an actionable design and decision-making tool (by talking about personas engaged in scenarios, etc, etc.). -- Dave Cronin

Adaptive Path: Making Strategy Tangible

Reading Adaptive Path's article on Marking Strategy Tanglible, I came across a brilliant definition of strategy. While the dictionary defines strategy as:

a plan of action or policy designed to achieve a major or overall aim

Jared Cole provides a more practical definition:

… a way of communicating the value of a pursuing a particular goal, the activities required to attain the goal, and the ways that leadership will guide the process.

undefined method `reenable' (Rake)

Having an issue with rake db:migrate? Update rake:

$ sudo gem update rake

Installing Feedzirra on CentOS 5.2 64-bit

I was installing Feedzirra gem on Centos 5.2 64-bit. It appeared I had a few 32-bit libraries installed instead of the 64-bit libraries which gave me a bunch of incompatible library messages. Anyway the following yum install and symlink got me on the right track:

sudo yum install libxml2-devel libxslt-devel krb5-devel libidn-devel
sudo ln -sf /lib64/libcom_err.so.2 /lib64/libcom_err.so

Hint: After updating a Bundle you should update Textmate Support

$ /Library/Application Support/TextMate
$ svn co http://svn.textmate.org/trunk/Support

For example, after updating the Ruby Bundle I got this error:

run_script.rb:1:in `require': no such file to load -- /Applications/Editors/TextMate.app/Contents/SharedSupport/Support/lib/tm/executor (LoadError) from /Users/user/Library/Application Support/TextMate/Bundles/Ruby.tmbundle/Support/RubyMate/run_script.rb:1

For more information about Bundles see the Textmate site. Credits: http://lists.macromates.com/textmate/2008-September/026802.html

Cannot connect with Capistrano or sFTP on CentOS

If you are trying to do a "get" operation with Capistrano and receive the following error:

/Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:156:in `[]=': undefined method `[]=' for nil:NilClass (NoMethodError)
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:207:in `handle_error'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:48:in `process!'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:43:in `loop'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:43:in `process!'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/transfer.rb:11:in `process'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/configuration/actions/file_transfer.rb:40:in `transfer'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/configuration/connections.rb:170:in `execute_on_servers'
 from /Library/Ruby/Gems/1.8/gems/net-ssh-2.0.3/lib/net/ssh/transport/algorithms.rb:296:in `each_slice'
  ... 17 levels...
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/lib/capistrano/cli/execute.rb:14:in `execute'
 from /Library/Ruby/Gems/1.8/gems/capistrano-2.5.3/bin/cap:4
 from /usr/bin/cap:19:in `load'
 from /usr/bin/cap:19

or a simple sftp connection and get the following error:

Request for subsystem 'sFTP' failed on channel 0

It is likely your sftp server is not running due to a mis-configuration in the /etc/ssh/ssh_config file. For CentOS 5.2 Final on a 64-bit architecture I made the following change:

  # The default is incorrect
  # Subsystem sftp /usr/lib/openssh/sftp-server
  Subsystem sftp /usr/libexec/openssh/sftp-server  

The restart ssh server using:

$ sudo /etc/init.d/sshd restart