@awead

Technical notes and explications of code

Glob-ins

A couple of months ago, I spent a harrowing Friday afternoon deploying one of my Rails apps. All the tests were passing on my laptop and on the development server. However, once I got the same code on the production box, none of the spec tests were running. Everything was failing with same error:

NameError:
   undefined local variable or method `id' for main:Object

Not a very helpful error. So I did some initial digging around, but that didn’t yield any explanations. What was even more exasperating was that the code and environment were exactly the same in both test and production. I know because I spent a lot of time checking.

I ended up really digging into the Rails source and tracked the problem down to a line in my rspec config:

spec_helper.rb
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RSpec.configure do |config|

  [...]

  config.global_fixtures = :all

  [...]

end

When specifying ActiveRecord fixtures, by default, rspec will look in spec/fixtures. If you load all of them in the folder, as I had specified above, it does a glob on the directory to build the list of fixtures.

In most cases, this probably doesn’t make a difference, but in my case it did because one fixture file had records that depended on the other. I had two fixture files, one for the users table and another for activities. Activities needed to be loaded first, which was happening on my laptop and on my development system. However, on my production server, the users fixture was loaded first instead. This at least explained the error message: Rails was complaining that it couldn’t find the “id” method because the activities records hadn’t been loaded yet.

The Goblin in the Glob

This left me puzzling over why files would load in a different order on two identical systems. It’s true that file globing will have different results with different operating systems, but the development and production systems were both CentOS 6, both updated with the same patches, ruby versions, and gems.

On the development system, I got:

irb(main):002:0> Dir["./*"]
=> [./activities.yml", "./users.yml"]

But production was:

irb(main):002:0> Dir["./*"]
=> ["./users.yml", "./activities.yml"]

I assumed that they would load alphabetically, but this was not the case. Ideally, you would just call .sort on the results and Ruby would then sort them alphabetically, but I needed to instruct Rspec to load them in a specific order. Fortunately, this was a one-line change:

spec_helper.rb
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RSpec.configure do |config|

  [...]

  config.global_fixtures = :activities, :users

  [...]

end

Another problem remained with cucumber, which also utilized the same fixtures and needed them specified in the same order. Again, another simple fix using ActiveRecord’s new FixtureSet methods:

ActiveRecord::FixtureSet.create_fixtures(File.join(Rails.root, 'spec', 'fixtures'), [:activities, :users])

No Answer

I still do not have an answer as to why the globing order would be different on the exact same operating system. Perhaps that will be the topic of another post.