[RailsConf 2024] From slow to go: Rails profiling hands-on

Transcript

1. None

2. From slow to go: Rails test profiling hands-on Vladimir Dementyev

   Evil Martians

3. palkan_tula palkan Why are we here? What's the plan? Who

   are you? 3 Warming up Or waiting for everyone's dip rspec to pass

4. palkan_tula palkan You are here = = your tests are

   slow 4

5. palkan_tula palkan Longer CI builds (also more expensive) Longer local

   runs (or "local CI" builds) 5 Slow tests

6. palkan_tula palkan Longer CI builds (also more expensive) Longer local

   runs (or "local CI" builds) Longer feedback loops More distraction, less productivity 6 Slow tests

7. palkan_tula palkan 🔍 Identify slowness causes and patterns 💊 Treat

   them well 🔁 Repeat until satisfied 7 From slow to go

8. palkan_tula palkan 8

9. palkan_tula palkan Specialized profiler for Ruby test suites Optimization toolbox

   to speed up tests with less refactoring 9 TestProf test-prof.evilmartians.io

10. palkan_tula palkan Used by GitHub, Discourse, Gitlab, Dev.to, and many

    more Used by YOU at this workshop! 10 TestProf test-prof.evilmartians.io

11. 11 github.com/palkan

12. 12 evilmartians.com

13. 13

14. palkan_tula palkan 14 X

15. palkan_tula palkan 15 Disclaimer: Mastodon team already did some test

    performance work (via TestProf), so I had to revert a few optimizations in the workshop's version of the codebase (so we can have more fun)

16. palkan_tula palkan General profiling (Stackprof, Vernier, sampling) Focused profiling (TagProf,

    EventProf) Factories overhead elimination (let_it_be) 16 The plan

17. palkan_tula palkan Local time: 8 : 30 ➡ 2 :

    30 CI time: 14 : 30 ➡ 8 : 00 17 Results

18. palkan_tula palkan Rails tests occupy only for a portion of

    a CI build time No need to optimize beyond other components 18 CI vs Rails tests

19. palkan_tula palkan General profiling 19

20. 20

21. palkan_tula palkan Workshop instructions 21 # rails_helper.rb TestProf::EventProf.monitor( Paperclip::Attachment, 'paperclip.post_process',

    :post_process )

22. palkan_tula palkan Workshop instructions 22 TAG_PROF=type \ TAG_PROF_FORMAT=html \ TAG_PROF_EVENT=sql.active_record,factory.create,

    sidekiq.inline,paperclip.post_process \ be rspec

23. palkan_tula palkan Coverage: opt-out ➡ opt-in gem "debug", require: false

    Webpacker: cache_manifest: true 23 Findings

24. palkan_tula palkan Logging—no effect when disk write is fast (SSD,

    Docker volumes on Mac) Thousands of I18n YAMLs—handled by Bootsnap 24 Findings

25. 25

26. palkan_tula palkan Do not require test-specific profiling skills Takes the

    most significant amount of time (sampling helps) Highlights low-hanging fruits 26 General profiling

27. palkan_tula palkan Focused profiling 27

28. palkan_tula palkan Similar tests has similar problems Focus on most

    time consuming test types, not individual outliers 28 Focused profiling

29. 29

30. palkan_tula palkan Reduced the number of tests to analyze by

    ~2x Divided tests into smaller groups (~1min run time) for further analysis 30 Focused profiling

31. palkan_tula palkan TagProf EventProf RspecStamp (RSTAMP) 31 Tools

32. palkan_tula palkan Sidekiq: inline! ➡ fake! Paperclip::Testing.fake! 32 Findings

33. 33

34. palkan_tula palkan Workshop instructions 34 # .rspec-local --tag ~paperclip:process

35. palkan_tula palkan 35 What's next?

36. palkan_tula palkan Factories 36

37. palkan_tula palkan 37 FPROF = 1 \ EVENT_PROF=factory.create \ be

    rspec spec/models Workshop instructions

38. palkan_tula palkan Factory cascades Too many disposable records (no reuse

    or recycle) Create vs. build 38 Factories vs. slow tests

39. 39

40. palkan_tula palkan FactoryProf RSpecDissect before_all / let_it_be 40 Tools

41. palkan_tula palkan No cascades found Many tests share the same

    context Reusing records between examples brings up to 6x speed up! 41 Findings

42. palkan_tula palkan Replacing let/let! with let_it_be works in ~90% of

    tests The rest may require some refactoring (usually minor) 42 Findings

43. palkan_tula palkan Every file must be treated individually (routine) Extracting

    shared contexts may help simplify future optimizations (e.g., adding fixtures) 43 Findings

44. palkan_tula palkan Homework 44

45. palkan_tula palkan Discover more TestProf tools (Autopilot, RuboCop cops, Factory

    Doctor) Make YOUR tests faster Become a Mastodon contributor! 45 Homework

46. Thank you Visit TestProf and Evil Martians at the Hack

    Day!