A Practical Taxonomy of Bugs and How to Squash Them-Keep Ruby Weird 2016

Catching software bugs is a mysterious magic, unknowable by science and untouchable by process.

False! Programming bugs, like real bugs, can be organized into a taxonomy. Come with me and I’ll show you how classification can help you build “programmer’s instinct” into a logical debugging process.

Transcript

1. A PRACTICAL TAXONOMY OF BUGS AND HOW TO SQUASH THEM
2. Instinctual Indications…2 Research Methods…9 Practical Taxonomy…12 Bohrbug…13 Schrödinbug…20 Fractalbug…24 Heisenbug…30 Mandelbug…36 Common Patterns…43 Resources…50 Table of Contents
3. Debugging Skills
4. “As you familiarize yourself with the application, you’ll build up some debugging instincts"
5. “Whenever I see something like this happening, the first thing I do is scan the logs to see if this process is completing or is sending a weird message.”
6. Debugging Instincts “ ”
8. “Whenever I see #{x}, I always check #{y}”
9. Research Methods • containment sometimes takes priority over squashing • we can only work with facts • we can’t squash every bug in this talk
11. Observable Attributes
12. Warning: Contrived Scenarios Ahead
13. A Practical Taxonomy of Bugs Upsettingly Observable Wildly Chaotic {
14. How to Squash Them
15. upsettingly observable bug #1 UPSETTINGLY OBSERVABLE
16. Observable Attributes is the bug observable in production? can it be reproduced locally? does it seem to be restricted to one area?
17. Bohrbug deterministic, highly reproducible UPSETTINGLY OBSERVABLE
18. Bohrbug Commonly found in code,sometimes on server UPSETTINGLY OBSERVABLE
19. Bohrbug likes to hide in complex branching in functions, classes or config UPSETTINGLY OBSERVABLE
20. Bohrbug In the wild: validation UPSETTINGLY OBSERVABLE
21. Reproduction & Resolution replicate locally and in test write the simple solution rewrite to be highly readable and extendable UPSETTINGLY OBSERVABLE
22. Bohrbug UPSETTINGLY OBSERVABLE
23. Bohrbug UPSETTINGLY OBSERVABLE
24. upsettingly observable bug #2 UPSETTINGLY OBSERVABLE
25. Observable Attributes how does this work? does this work? wait, what is this even testing? did this ever work?
26. Schrödinbug stick-like body appendages look like twigs UPSETTINGLY OBSERVABLE
27. Schrödinbug Likes to pretend to be working code. On close inspection, reveals itself to be a bug. UPSETTINGLY OBSERVABLE
28. Schrödinbug In the wild: code that never worked UPSETTINGLY OBSERVABLE
29. Schrödinbug In the wild: it didn’t work how you thought it did UPSETTINGLY OBSERVABLE
30. Logging as Verification Tool
31. Git Bisect Tool
32. Reproduction & Resolution reproduce the “broken” state locally and in test add log statements until you can verify what causes the broken state. if the bug did work at some point, find the point at which it did work. write tests to represent the configuration and flow of the fixed state
33. Schrödinbug UPSETTINGLY OBSERVABLE
34. Schrödinbug UPSETTINGLY OBSERVABLE
35. wildly chaotic bug #1 WILDLY CHAOTIC
36. Observable Attributes Does it appear non-deterministic? Does it seem to disappear once you observe or debug it?
37. Heisenbug “now you see it, now you don’t” WILDLY CHAOTIC
38. Heisenbug WILDLY CHAOTIC In the wild: a heisenbug that lives in code
39. Heisenbug WILDLY CHAOTIC In the wild: a heisenbug that lives in data
40. Profiling for Verification https://kcachegrind.github.io/html/CallgrindFormat.html Tool
41. FLAME GRAPHS http://www.brendangregg.com/FlameGraphs/cpu-mysql-updated.svg Tool
42. Reproduction & Resolution use profiling to find the trigger state use the app (not fixtures or DB manipulation) to get the data in this state recreate that state in test follow borhbug instruction
43. Heisenbug WILDLY CHAOTIC
44. Heisenbug WILDLY CHAOTIC
45. wildly chaotic bug #2 WILDLY CHAOTIC
46. Observable Attributes is everything broken? all of it? send help??
47. Mandelbug WILDLY CHAOTIC
48. Mandelbug seems like everything is broken at once WILDLY CHAOTIC
49. Mandelbug people are very upset with you WILDLY CHAOTIC
50. Mandelbug likely an issue with your system, not code WILDLY CHAOTIC
51. “The bug is huge and everywhere at once. SQL: could not connect to server: Connection refused was bubbling up all over the place. Jobs won’t run, emails won’t send, every submit button on the site fatal errored.” on-call log 24 June 2014 WILDLY CHAOTIC
52. Disk Usage Tool df -h
53. Reproduction & Resolution attempt to connect to server & view logs use df -h to find if all the storage is being used can that be restarted, rotated or killed at this time?
54. Mandelbug WILDLY CHAOTIC
55. Mandelbug WILDLY CHAOTIC
56. A Practical Taxonomy of Bugs Upsettingly Observable Wildly Chaotic { bohrbug schrödinbug mandelbug heisenbug
57. “Debugging Instincts”
58. “Debugging Instincts”
60. Resources • “Linux Debugging Tools I Love”, Julia Evans • Systems Performance, Brendan Gregg • “Why Do Computers Stop and What Can Be Done About It?”, Jim Gray • “Debug Patterns for Efficient High- levelSystemC Debugging”, Frank Rogin, Erhard Fehlauer, Christian Haufe, Sebastian Ohnewald