After two release candidates in the last few weeks, Rails 2.2 has finally been released. Although the version number doesn't indicate a huge step, there are a lot of new features in Rails.
Internationalization
A long anticipated issue finally resolved—Rails now offers a framework for internationalization tasks. Mind that this doesn't mean that Rails now supports any other locale than en-US out of the box, it just makes it easier to hook other internationalization implementations into Rails. Sven Fuchs explains the goals and motivation of Rails' internationalization support in his blog:
The first part is the API itself which is just a Ruby module with a bunch of methods that will be used by Rails and delegate all requests to a backend.
The second part is the Simple backend which implements whatever is necessary to re-localize Rails back to en-US.
If you would rather see a quick example, have a look at Trevor Turk's simple localization blog.
Thread Safety
With version 2.2, Rails is finally thread-safe, thanks to Josh Peek's Google Summer of Code project. With this step also comes the necessity of connection pools. But what does thread safety actually mean for Rails? From the release notes:
Depending on your web server infrastructure, this means you can handle more requests with fewer copies of Rails in memory, leading to better server performance and higher utilization of multiple cores.
JRuby's Charles Nutter also wrote a detailed blog entry answering that question: "it means removing the single coarse-grained lock around every incoming request and replacing it with finer-grained locks around only those resources that need to be shared across threads".
Improved Documentation
The internal documentation of Rails has been improved at many places, and there's also the Ruby on Rails guides site with many extensive and profound articles on topics such as security, testing, debugging.
Other changes include the new mailer layouts, or comfortable memoization to make your code more readable. Another new feature is the simpler conditional get support, which we already covered in a recent Rails roundup on ETags. Some last minute changes were done in RC2, namely the improvement of the request forgery protection and tuning of the ActiveRecord connection pooling code.
Upgrading
There are a lot more changes than what we've presented here, you can find a more comprehensive list in the Rails 2.2 release notes.
Rails 2.2 depends on very recent Ruby Gems 1.3.1 installation. If you are having trouble with the update of Ruby Gems, take a look at Eric Hodel's blog for details.
Afterwards, you should be all set to install Rails:
gem install rails