require() bombed my multi-threaded app!
summary
A Ruby app crashes under Sidekiq when autoloading mixes with manual requires causing double loads, constant redefinition warnings and hard-to-trace circular dependencies; Ruby 2 fixes autoload thread safety but ActiveSupport defaults to autoload vs require using Kernel.load which triggers repeats. Fixes: switch ActiveSupport to require, use eager_load_paths (not nested autoload paths), and adopt an isolated spec helper. Real results: three codebases drop test startup from 5–10 minutes to ~30 seconds; reproducing the original bug takes ~6 months of debugging.
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chapters (7)
- 0:00Introduction and setup
- 3:36Ruby code loading basics
- 15:27Active Support and autoloading
- 28:26Circular dependencies explained
- 31:58Rails autoload paths pitfalls
- 36:11Optimizing Rails test suites
- 39:01Best practices and takeaways
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