2010-09-24 00:11:00 +0000
RubyX are the maintainers for the RailsPlugins.org website with hosting kindly donated by EngineYard. As the site is all about compatibility with Rails 3, the irony was not lost on us that the site is running on Rails 2.3.5. I will do a series of posts which cover how we updated the site to Rails 3.
First off, RailsPlugins.org is a non trivial web application. It has OpenID authentication, API integration with RubyGems.org as well as a complex versioning, voting and commenting system that includes emails out to gem owners to encourage them to get their gems up to date with Rails 3.
The site currently hosts information for over 500 plugins and gems, tracking 1,500 versions with over 6,500 opinions from users and owners alike.
First off, it is good to work out a broad process on how you plan to upgrade a Rails 2.x app to Rails 3. At RubyX, this is one of our specialties, and so we have a documented path on how we go about it.
RubyX Rails 3 Upgrade Process from Rails 2.3.x
As I mentioned, RubyX have a codified path on how we update Rails 2.3 apps to Rails 3. If you are running a version of rails that is earlier than Rails 2.3, you really need to update to 2.3.x first before trying to go to Rails 3. It will save you a lot of pain.
- Confirm all specs, tests and features are passing
- Migrate the 2.3.x app over to using Bundler and a Gemfile
- Remove all vendor’d gems and plugins that can be specified in the Gemfile
- Audit any remaining vendor’d gems and plugins that have application specific modifications, and fork these changes into our own repositories and install them from here using the Gemfile
- Review all gems and plugins in use by the app and ensure that Rails 3 versions are available.
- For any remaining vendor’d gems and plugins that can not be Gemfile’d now but do have a Rails 3 version, leave them vendor’d for now and migrate to the gem version once we have updated t Rails 3.
- For any gems that do not have a Rails 3 version, decide what to do. Contribute a Rails 3 version or replace.
- Deploy this code to staging environment, for a sanity check.
- Migrate the Rails app release by release up to Rails 2.3.9
- Handle all deprecation warnings at each release
- Migrate Gemfile and app to Rails 3
- Update gem dependencies to ensure working with Rails 3
- Do minimal modifications required to get all tests and specs passing
- Review application code and take advantage of new Rails 3 idioms
- Deploy to cloned production environment and test fully
- Deploy to production environment with roll back plan
Obviously the above gets run in a separate branch, it also gets done as rapidly as possible to avoid divergence with the production branch. There are several opportunities to merge back into production, at each update of Rails before 3.0 for example. However, this is not required.
A key point is step 6, making sure you have Rails 3 compatible versions of all gems you use in the app. This can obviously be done earlier, however, upgrading to Rails 2.3.9 is a good thing to do in any case and can be the first goal of your migration process.
You can use RailsPlugins.org to look up your gems and plugins to see what other users have found and authors have commented on in relation to Rails 3 compatibility.
So with the process codified. Lets get onto our first step, making sure the app has test coverage.
Confirm all specs, tests and features are passing
In doing this sort of upgrade you really can’t stress a good test suite enough. RailsPlugins has XXXX specs and XXXX features that exercise every part of the application, very thoroughly. So before we start changing code or files, lets run that suite:
$ rake spec .................... (...) Finished in 20.469918 seconds 234 examples, 0 failures $ rake cucumber .................... (...) 126 scenarios (126 passed) 1873 steps (1873 passed) 1m7.546s
OK, it could be a lot faster, but we have the green light on all our specs and features. Time to migrate the app to use Bundler and a Gemfile.
Migrate the 2.3.x app to use Bundler and a Gemfile
Now that we have spec coverage for our changes, the next thing we need to do on a Rails 2.3 app is to create a config/preinitializer.rb file as well as update your config/boot.rb to boot using Bundler. This is well explained on the Bundler website. Just follow along there.
In the case of RailsPlugins.org, we were already used a Gemfile, of sorts. It was running a 0.9 release of bundler, and the Gemfile looked like this:
source :gemcutter gem 'rails', '2.3.5' gem 'mysql', '2.8.1' gem 'url_field', '0.0.2' gem 'ruby-openid' gem 'hoptoad_notifier' gem 'capistrano' gem 'engineyard', '1.1.3' gem 'delayed_job', '2.0.2' group :plugins do gem 'authlogic-oid', :require => 'authlogic_openid' gem 'authlogic', '2.1.3' gem 'behavior', '0.2.0' gem 'will_paginate', '2.3.11' gem 'inherited_resources', '1.0.4' end group :test do gem 'highline', '~> 1.5.2' gem 'machinist', '>=1.0.3' gem 'cucumber', '>=0.3.103' gem 'cucumber-rails', '>=0.2.4' gem 'database_cleaner', '>=0.4.3' gem 'webrat', '>=0.6.0' gem 'rspec', '>=1.3.0' gem 'rspec-rails', '>=1.3.2' gem 'rspec', '>=1.2.9' gem 'faker', '~>0.3.1' gem 'nokogiri' gem 'ruby-debug' gem 'ZenTest' end
The above Gemfile is not TOO bad, but there are some three glaring mistakes.
Firstly is the use of “>=” While this is limited to the test group, it is also just plain not a good idea as it means any equal to or higher version of the version specified. Using “~>” is much safer as it limits updates to point releases.
Secondly, is the use of the “:plugins” group. This group is there to make sure that Bundler will check the dependency requirements for this group when you bundle install, as all of these gems are in the plugins directory and without any mention in the Gemfile, Bundler would not be able to check for dependency conflicts.
Thirdly, several production gems requirements have no version attached. This is dangerous.
So, first thing to do is get version numbers on all of those gems. And the best way to do that is to log into the production environment and do a gem list.
Doing this found the following versions for the production gems we had no versions for:
hoptoad_notifier (2.2.0) ruby-openid (2.1.2)
Additionally, we no longer use capistrano for deployment, instead relying on the nice EngineYard command line gem to handle this.
So we insert those version numbers, and delete capistrano and we get (without including the test group for now):
source :gemcutter gem 'rails', '2.3.5' gem 'mysql', '2.8.1' gem 'url_field', '0.0.2' gem 'ruby-openid', '2.1.2' gem 'hoptoad_notifier', '~> 2.2.0' gem 'engineyard', '1.1.3' gem 'delayed_job', '2.0.2' group :plugins do gem 'authlogic-oid', :require => 'authlogic_openid' gem 'authlogic', '2.1.3' gem 'behavior', '0.2.0' gem 'will_paginate', '2.3.11' gem 'inherited_resources', '1.0.4' end
With this in place, we do a bundle install followed by running our test suite, to make sure that our changes don’t break anything.
With the specs and cukes green, we can commit the above work as the first step complete.
Remove all vendor’d gems and plugins that can be specified in the Gemfile
Next step is to get rid of that plugins group, and instead use gems or github sources directly.
Looking in the vendor/plugins directory of RailsPlugins.org, we see:
email@example.com ~/Code/railsplugins $ ls vendor/plugins/ delayed_job formatted-dates high_voltage hubahuba open_id_authentication project_search timeline_fu url_field
Sharp eyes will note that we have some duplication between here and the Gemfile. Lets remove that.
Now doing this is time consuming. The steps are as follows:
- Inspect the vendor/plugins/plugin directory and see if it has a gemspec.
- If there is a gemspec, get the version and create an appropriate line in the Gemfile locked to that version
- If no gemspec, search RailsPlugins.org, RubyGems.org or the appropriate plugin home page for the right gem version to use for a Rails 2.3 app and then put this in the Gemfile
- If no gemspec and no gem released, skip and go to the next one.
- Once the gemfile has the right version, remove the vendor/plugins directory entirely
- Check the various environment.rb files (main, production, development, testing etc) and remove any config.gem line that relates to this gem. Use any information gleaned here to update the Gemfile line
- Do a new bundle install
- Run all specs or tests and cukes again and make sure you are still green
- Handle any requirement errors or coding errors (if doing this has forced you onto a different incompatible gem version)
- Once all specs and cukes are green, repeat with the next directory.
The above can take time.
In our case, we had a few situations.
a) We had a pluginized version of hubahuba, but in the entire app, this plugin was used ONCE. So instead, I removed the code we were using and made a lib/file that implemented the code we needed and just nuked the directory. Less code is good.
b) We were not using project_search any more. So this got the boot.
c) high_voltage is a gem, but that Gem only works on Rails 3. As I know that the Rails 3 version is available we will leave it vendor’d for now as there is no point doing anything else with it.
With all that done, our Gemfile looked like this:
source :rubygems gem 'rails', '2.3.5' gem 'mysql', '~> 2.8.1' gem 'url_field', '~> 0.0.2' gem 'ruby-openid', '~> 2.1.7' gem 'rack-openid', '~> 1.0.3' gem 'hoptoad_notifier', '~> 2.2.5' gem 'engineyard' gem 'will_paginate', '~> 2.3.11' gem 'delayed_job', '~> 2.0.0' gem 'authlogic', '2.1.3' gem 'behavior', '~> 0.2.0' gem 'inherited_resources', '~> 1.0.4' gem 'formatted-dates', '~> 0.0.1' gem 'timeline_fu', '~> 0.3.0' group :test do gem 'ZenTest' gem 'highline', '~> 1.5.2' gem 'machinist', '>=1.0.3' gem 'cucumber', '>=0.3.103' gem 'cucumber-rails', '>=0.2.4' gem 'database_cleaner', '>=0.4.3' gem 'webrat', '>=0.6.0' gem 'rspec', '>=1.3.0' gem 'rspec-rails', '>=1.3.2' gem 'faker', '~>0.3.1' gem 'nokogiri' gem 'ruby-debug' end
With only high_voltage left in vendor/plugins from the original bunch.
However, I needed to add in open_id_authentication and a fork of authlogic_openid to get OpenID working again. Looking through the various codes, it looks like authlogic has some issues with OpenID at the moment, so part of the Rails 3 update may be converting to Devise.
Note also how I changed the requirements to be “~>” instead of locked at a version. If you do this, run bundle update once and run all your specs again to make sure everything passes. Then commit your Gemfile.lock to your source control so the same version gets deployed on your production environment.
Deploy this code to staging environment, for a sanity check.
Next step is to deploy our new Gemfile based Rails app to a staging environment. On EngineYard this is painfully easy to do, simply snapshot your production environment, and then clone it to a new name (staging). Once done, boot up your app and do an ey deploy -e staging. For other hosts, I am sure you will know how to do this as well.
We ran into a problem in doing this. Our production RubyGems.org was still running on 1.8.6 and there was a gem requiring Ruby 1.8.7 as a minimum. So we updated our Ruby version to 1.8.7 and tried again. Due to this we now know that we will have to update our production environment to 1.8.7, so I scheduled a time to do this on the website, which gave me a good opportunity to use the new sites feature from tellthemwhen.com
This is what our command line deploy looks like:
$ ey deploy -e staging Beginning deploy for 'railsplugins' in 'staging' on server... Successfully installed engineyard-serverside-1.3.3 1 gem installed ~> Deploying revision e94f047... Removing project_search, don't need that ~> Pushing code to all servers ~> Starting full deploy ~> Copying to /data/railsplugins/releases/20100923133736 ~> Ensuring proper ownership ~> Gemfile detected, bundling gems ~> Symlinking configs ~> Migrating: cd /data/railsplugins/releases/20100923133736 && PATH=/data/railsplugins/releases/20100923133736/ey_bundler_binstubs:$PATH RAILS_ENV=production RACK_ENV=production MERB_ENV=production rake db:migrate --trace ~> Symlinking code ~> Restarting app servers ~> Cleaning up old releases Deploy complete
Now the staging environment deployed and tested OK, it’s time to update the production site during the scheduled maintenance window and then move onto the next step, Migrate the Rails app release by release up to Rails 2.3.9.
For that, I will leave until the next post.