Rails migrations: creating a MySQL BIGINT

add_column :facebook_user_id, :integer, :limit => 8 # BIGINT

Running individual tests with rake

rake TEST=test/units/foo_test.rb

Source: http://rails.lighthouseapp.com/projects/8994/tickets/168-patch-generators-create-tests-with-require-test_helper-which-doesn-t-work

Ruby: returning an array of single attributes from an array of objects

You can do this:

animals.collect(&:name)

…to return an array of animal names. This is essentially a shorthand version of:

animals.collect { |animal| animal.name }

Source

Ignore columns in a legacy database with ActiveRecord

Add this to the model:

# prevent ActiveRecord stumbling on the column named 'hash' 
# by removing it from the column list
  class << self # Class methods 
    alias :all_columns :columns 
    def columns 
      all_columns.reject {|c| c.name == 'hash'} 
    end 
  end

Solution half-inched from: http://groups.google.com/group/compositekeys/msg/202d04713ecbd6ee

ActiveRecord: has the object been saved to the database yet?

Cleaner than checking if the value of fruit.id is nil:

fruit.new_record?

Rails controller: logic for a specific request format

  if request.format.html?
    # do stuff
  end

Works for any valid MIME type…

  if request.format.xml?

More details at http://ryandaigle.com/articles/2007/2/15/what-s-new-in-edge-rails-mime-type-convenience-methods

Rails: access the controller name in the view

@controller.controller_name

Writing to the Rails log

RAILS_DEFAULT_LOGGER.error('log message')

…will write to the log file of the current environment.

Rails console reload

When you make changes to your model objects, you can reload them in the console using:

reload!

Rails with Mongrel on Plesk

I set up Mongrel on a server using Plesk 7. Each Rails app has a single Mongrel webserver¹ running on the local interface (port 8001 and up). The Mongrel webservers are not accessible to the outside world. They are proxied through Apache using mod_proxy. Just add this snippet to the vhost.conf for the appropriate domain:

ProxyRequests Off
ProxyPreserveHost On
ProxyPass / http://0.0.0.0:8001/
ProxyPassReverse / http://0.0.0.0:8001/

Replace 8001 with the chosen port for your app. (The block does not need to be inside a VirtualHost or Directory container.) Remember to rebuild the Plesk configs afterwards with:

/usr/local/psa/admin/sbin/websrvmng -a -v

You’ll now need to add a Mongrel webserver for the app in /etc/init.d/mongrel:

apps = {
  'firstapp'=> 8001,
  'secondapp' => 8002
}

Enter the app name and your chosen port number into the ‘apps’ hash, and save the file.

Deployment with Capistrano

You’ll now need to get your Rails app ready to deploy using Capistrano. Open a shell and navigate to a working copy of your app. Then run:

capify .

This will generate some Capistrano files in your working copy folder, including a generic deployment recipe (deploy.rb). We need to customise deploy.rb to work with our setup. If the SVN repository isn’t accessible from the live server, you’ll also need to install a Capistrano module to enable use of a local Subversion repository - download from here: Capistrano module for local SVN access The zip file contains two .rb files that you’ll need to put into your app’s lib/tasks directory. Make sure you add and check in all of the Capistrano files to Subversion when you’re done. Now we’re ready to deploy the app for the first time. In your working copy directory, do:

cap deploy:setup
cap deploy

This will export the latest copy of your project from Subversion, upload it to the server, and start Mongrel. To update the version of your app on the server, use:

cap deploy

If you have any problems with your release, you can easily roll back to the previous version with:

cap deploy:rollback

Importing and updating your database

To import your schema for the first time, upload your db/schema.rb if you haven’t already. Then, on the live server, do:

RAILS_ENV=production rake db_schema_import

The RAILS_ENV=production part ensures that the production database details are used by rake. If your database is already on the live server and you need to run migrations against it, you can do:

RAILS_ENV=production rake db:migrate

Or from kermit:

cap deploy:migrations

How apps are stored

It is not essential to know this, because this is all done for you by Capistrano! All Rails applications live in the /u/apps/ directory. Every time you do a ‘cap deploy’, a new dated folder is created in the /u/apps/APPNAME/releases folder. For example:

# ls -l /u/apps/firstapp/releases/
drwxr-xr-x  13 root root 4096 Dec 18 14:48 20061218144553
drwxr-xr-x  13 root root 4096 Dec 18 15:23 20061218152030
drwxr-xr-x  13 root root 4096 Dec 18 15:54 20061218155131

The most recent release is symlinked to /u/apps/APPNAME/current. This is where Mongrel serves the application from. Some files (including log files) are shared between releases, so you don’t lose them when you deploy a new version. These live in the /u/apps/APPNAME/shared folder. If you’re concerned about the releases folder getting too full, you can delete all but the most recent 5 releases with:

cap deploy:cleanup

Footnotes

1. I had intended to set up Rails using a Mongrel cluster but you need Apache 2.1 or higher to use mod_proxy_balancer.

2. Plesk password protection will not work. All requests to the domain are proxied to Mongrel, so Apache auth is ignored.

Links

• Excellent Capistrano cheatsheet