I’ve had this Rails 2.3.2 app running on an Amazon EC2 small instance since March 2009. The app does some back-end processing for the media player software I created for SecondLife. The App stack is nginx, Rails 2.3.2, and some Mongrels. I decided to switch to a micro instance. This will cut my monthly bill from $60 to around $15. The 613MB RAM available on the micro-instance should be more than enough for my app. Amazon also just announced free basic resource monitoring for EC2 instances which means i can easily monitor resource usage to be sure my app isn’t running out of resources.
Packaging Rails Apps with Bundler
I first discovered Bundler while looking for an easy way to deploy Ragios. Ragios now uses Bundler for dependency management. With bundler I can just package my Rails app with all its dependencies (gems) and copy it to a new system. Bundler will install the right version of all the rubygems required for my app to run on the new system.
This is how I used it;
On the old Server
First install the Bundler Rubygem
sudo gem install bundler
Change directory to the root of your rails app
Create a GemFile for your rails app
The Gemfile is created in the root directory of your rails app.
Edit the Gemfile and add the gems used by your app.
gem "rails" , "2.3.2"
Include version number if you want bundler to use a specific version of the gem.
In my case, I wanted every gem on the new server to be exactly the same version as the gems on the old server. So I added version numbers for each gem.
If you want to list all the gems on your system to see their version number, run the ‘gem list’ command;
Below is a copy of my Gemfile:
source "http://rubygems.org" gem "rails", "2.3.2" gem "hpricot","0.8.1" gem "simple-rss","1.2" gem "rake","0.8.7" gem "mongrel","1.1.5" gem "mongrel_cluster","1.0.5"
You don’t need to add every gem on gem list to your Gemfile. You just need the gems you installed and required on your app. Bundler will detect the rest and install all dependencies. Example activesupport, actionmailer etc. will be installed by Bundler for the Rails gem.
sudo bundle install
With this command, bundler will download and install all the listed gems and their dependencies. If you already have the gems installed on your system, bundler will use the one you already have. Below is the output from running bundle install with my Gemfile;
Fetching source index for http://rubygems.org/ Using rake (0.8.7) Using activesupport (2.3.2) Using actionpack (2.3.2) Using actionmailer (2.3.2) Using activerecord (2.3.2) Using activeresource (2.3.2) Using cgi_multipart_eof_fix (2.5.0) Using daemons (1.1.0) Using fastthread (1.0.7) Using gem_plugin (0.2.3) Using hpricot (0.8.1) Using mongrel (1.1.5) Using mongrel_cluster (1.0.5) Using rails (2.3.2) Using simple-rss (1.2) Using bundler (1.0.7) Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.
When you run bundle install, it will creates a file Gemfile.lock, this file contains a map of all your gems and their dependencies. Bundler will use this file to install gems on the new server.
Now copy the entire directory of your rails app to the new server. Make sure you have Gemfile and Gemfile.lock in the root directory of your Rails app when you copy it to the new server.
On the new server
With your Rails app now copied to this server,
sudo gem install bundler
Change directory to the root of your rails app;
Run bundler to download and install the gems required for your rails app to run on this server
After this, your Rails app is ready to run on the new server. You can test it with WEBrick.
I then installed Apache and Phusion Passenger.
Ruby has come a long way, it took only a few minutes to move the app from the old server and setup it up on a new server.
You can see I also switched the app from nginx/mongrels to Apache/Passenger.
There are other ways to use bundler with Rails 2.3, since this is the only Rails app I plan to run on this server, I simply needed Bundler to install the right version of all my gems globally in the system for MRI to use.
Hope this was helpful.
More info on Bundler here.