TIL, 2018-02-06

Musings

• HN/Rust: Skylight uses an agent embedded in Rails applications. Ruby = high memory, C++ = high risk of crashes.
  • 92% smaller than Ruby agent.

Optimize Rails performance bottleneck with caching and Rack middleware

Reference

• Redis for slow AR queries. For Heroku, you can have Redis to Go.
• Sidekiq Cron used to update the cache every half an hour.
• A Redis hit means no database query and also reduces memory usage because you don’t need to instantiate ActiveRecord objects.
• Rack middleware: You can create your own middleware, so that the app doesn’t pass through Rails.

Limit Rails memory usage, fix R14 and save money on Heroku

Reference

• gem derailed_benchmarks to see which gems consume a lot of memory.
• jemalloc as an alternative to the official MRI memory allocator.
• Limiting concurrency and workers. Just 1?
• Optimize JSON parsing? gem yaji-ruby.

Ruby under a Microscope

• defs/keywords contains all the keywords in Ruby.
• redo and retry are used to execute parts of the loop. redo repeats the current iteration, retry repeats the whole loop from the start. Reference
• undef apparently is a reserved word, but how would you use it?
  • Reference
  • Reference
  • This is used in things like mocking.
  • Rails codebase: Used for testing the behavior of classes with and without modules mixed-in.
  • This can be used for blocking a class explicitly defined in the superclass.
  • For mixins: you can include the whole mixin, but remove the methods it shouldn’t support. Ex: in the graphics library shoes, the button class mixes in clickable, but undef’s the release method because buttons don’t support it.
• You can sort of include methods dynamically.
  • Form.send(:include, FormExportingMethods) if you really need to.

99 Bottles of OOP

• Shameless green.
• Transformation Priority Premise: It makes sense, but it’s like, too robot-like/nuanced?
• Tests: Sometimes it’s just better to test the hardcoded strings rather than pass through a function.