So this morning I upgraded the suite of Rails apps (7 in total) that make up the product that I've been building from Rails 5.0.2 to 5.1.3. I took my usual, slow as a turtle, approach to doing this upgrade (5.1.4 has now reached RC1 status which means that 1 release behind is uite stable by now). The main change driving my desire to upgrade was the improved low level connection handling in ActiveRecord which should make developing multi-tenant applications better.

Here are a few notes on upgrading to Rails 5.1.

The Lines to Change in Gemfile

Previously I had:

gem 'rails', '~> 5.0.2'
gem 'puma', '~> 3.0'

which I changed to

gem 'rails', '~> 5.1.3'
gem 'puma', '~> 3.10'

The reason for the Puma update turned out to be unneeded but it is a core part of my stack so it is likely good to upgrade.

Useful Links

Don't Be Afraid to Delete Gemfile.lock and Re Bundle

Out of my seven apps, all built on top of the same version of Rails, two had problems with:

bundle update rails puma

These two applications had issues with the font-awesome-rails gem and railties. Rather than try and monkey around with them, I simply did a:

git rm Gemfile.lock

and then a:

bundle install

And that fixed everything.

Puma Now Needs a Space Before the Port

Right after my Rails update and before I did the Puma update, I got this bit of joy when I started my server:

bundle exec rails s -p3203
=> Booting Puma
=> Rails 5.1.3 application starting in development on http://localhost:3203
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.10.0 (ruby 2.3.1-p112), codename: Russell's Teapot
* Min threads: 2, max threads: 2
* Environment: development
* Listening on tcp://
/Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:270:in `initialize': getaddrinfo: nodename nor servname provided, or not known (SocketError)
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:270:in `new'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:270:in `add_tcp_listener'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:105:in `block in parse'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:88:in `each'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/binder.rb:88:in `parse'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/runner.rb:144:in `load_and_bind'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/single.rb:87:in `run'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/puma/launcher.rb:183:in `run'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/puma-3.10.0/lib/rack/handler/puma.rb:69:in `run'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/rack-2.0.3/lib/rack/server.rb:297:in `start'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/commands/server/server_command.rb:44:in `start'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/commands/server/server_command.rb:131:in `block in perform'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/commands/server/server_command.rb:126:in `tap'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/commands/server/server_command.rb:126:in `perform'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/thor-0.20.0/lib/thor/command.rb:27:in `run'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/thor-0.20.0/lib/thor/invocation.rb:126:in `invoke_command'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/thor-0.20.0/lib/thor.rb:387:in `dispatch'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/command/base.rb:63:in `perform'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/command.rb:44:in `invoke'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_admin/gems/railties-5.1.3/lib/rails/commands.rb:16:in `<top (required)>'
        from /Users/sjohnson/Dropbox/fuzzygroup/hyde/seira_watch/seira_admin/bin/rails:9:in `require'

This turned out to be a change somewhere in Rails where a space is now needed between the -p and the port number, so this:

bundle exec rails s -p3203

needs to be:

bundle exec rails s -p 3203

This was covered in this Github Issue. Supposedly the latest version of Puma restores the previous functionality where a space isn't needed but I have NOT found that to be so. The solution was to simply accept that a space after -p is required. Technically I could have not upgraded Puma but it feels like running the current version of is always a good thing.

Middleware Now Needs a Class Constant Not a String

What I am building uses a multi-tenant approach based on the Apartment gem and this requires an initializer that specifies a middleware layer. Prior to Rails 5.1, this was done as follows:

Rails.application.config.middleware.use 'Apartment::Elevators::Subdomain'
(in config/initializers/apartment.rb)

When I first started my application using Rails 5.1, I got this unpleasant result:

 bundle exec rails s -p 3210
=> Booting Puma
=> Rails 5.1.3 application starting in development on http://localhost:3210
=> Run `rails server -h` for more startup options
/Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/actionpack-5.1.3/lib/action_dispatch/middleware/stack.rb:35:in `build': undefined method `new' for "Apartment::Elevators::Subdomain":String (NoMethodError)
Did you mean?  next
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/actionpack-5.1.3/lib/action_dispatch/middleware/stack.rb:99:in `block in build'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/actionpack-5.1.3/lib/action_dispatch/middleware/stack.rb:99:in `each'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/actionpack-5.1.3/lib/action_dispatch/middleware/stack.rb:99:in `inject'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/actionpack-5.1.3/lib/action_dispatch/middleware/stack.rb:99:in `build'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/railties-5.1.3/lib/rails/engine.rb:508:in `block in app'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/railties-5.1.3/lib/rails/engine.rb:504:in `synchronize'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/railties-5.1.3/lib/rails/engine.rb:504:in `app'
        from /Users/sjohnson/.rvm/gems/ruby-2.3.1@seira_watch/gems/railties-5.1.3/lib/rails/application/finisher.rb:45:in `block in <module

Apparently middleware layers that used to take a string now need a class constant so this needs to be rewritten as:

Rails.application.config.middleware.use Apartment::Elevators::Subdomain

This is discussed in this Rails Issue

skip_before_filter Is Now skip_before_action

Although I was able to start my application correctly in development mode with a still in place skip_before_filter, when I tried it in production, I got:

=> Run `rails server -h` for more startup options
/Users/sjohnson/Dropbox/fuzzygroup/hyde/seira_watch/seira_watch_web_app/app/controllers/api_controller.rb:3:in   `<class:ApiController>': undefined method `skip_before_filter' for ApiController:Class (NoMethodError)
Did you mean?  skip_before_action

This was an easy change but it is still something that could easily trip you up. Obviously I have been seeing the deprecation warnings for some time now and it is my bad for not having made these changes.


While mildly annoying these are relatively small issues htat I was able to work around quite cleanly. The total time to upgrade 7 Rails apps from 5.0.2 to 5.1 was less than an hour in total even including the research and deploy time. Recommended.

Public Service Announcement

If you haven't upgraded your Ruby Gems executable, you likely should. More details are here.