Some kind of race condition in v0.3.21

[hron]

I've stumbled upon a very strange error after the upgrade of mysql2 gem from 0.3.20 to 0.3.21. Here is the exception the app raises on a very simple code.

Couldn't find Thing with id=100 [WHERE `things`.`id` = 33]
  vendor/bundle/ruby/2.1.0/gems/activerecord-3.2.22/lib/active_record/relation/finder_methods.rb:344:in `find_one'

The code is very simple:

Thing.find(100)

The app is run by unicorn, here is the exact versions of essential software:

• Ruby 2.1.5
• Ruby on Rails: 3.2.22.5
• Unicorn: 4.9.0 (I also tried 5.1.0)
• mysql2 0.3.21.

The exception is generated only under load and after some time. There is clearly some kind of race condition. Downgrading mysql2 to 0.3.20 resolves the problem. Let me know if you need any other information.

[hron]

@sodabrew Maybe this is related to 1bdda90?

[sodabrew]

Interesting, hm.