The 4 Horsemen of Bad Rust Code

Slide 1

Slide 1 text

No content

Slide 2

Slide 2 text

No content

Slide 3

Slide 3 text

No content

Slide 4

Slide 4 text

About me • Living in Düsseldorf, Germany • Backend engineer, open source maintainer, consultant at corrode.dev • Using Rust since 2015 • "Hello Rust" YouTube and "Rust in Production" Podcast

Slide 5

Slide 5 text

The Four Horsemen of Bad Rust Code Ignorance Excessive Abstraction Premature Optimization Omission

Slide 6

Slide 6 text

I. Ignorance

Slide 7

Slide 7 text

Ignorance • Uses "stringy-typed" APIs • Mutates liberally • Bad or no error handling • Lack of architecture • Prototype-style code

Slide 8

Slide 8 text

Ignorance: Red Flags • Imperative code • Magic return values (-1, "") instead of errors • Everything is a string • u nwr a p() • "c l on e () all the things!" • "mut"

Slide 9

Slide 9 text

Introducing the task

Slide 10

Slide 10 text

No content

Slide 11

Slide 11 text

Rusty Rooms Residences;Brussels;2023-04-12;Deluxe;132.19 Ferris Motel One;Athens;2024-10-09;Family;227.43 Cargo Cabin;Oslo;2023-01-24;Double;170.17 Lifetime Lodge;Istanbul;2024-10-15;Family;177.94 Mutable Manor;Budapest;2023-03-26;Executive;197.24 Ownership Oasis;Prague;2024-11-07;Suite;77.94 Pattern Palace;Madrid;2023-03-17;Executive;195.5 Trait Towers;Amsterdam;2024-05-06;Double;141.94 Async Apartments;Rome;2023-06-28;Single;84.36 Binary Bungalows;Dublin;2024-05-01;Executive;146.57 Crates Cottage;Athens;2023-03-05;Suite;248.67 Data Den;Paris;2023-11-19;Single;238.3 Enum Estate;Berlin;2024-06-12;Double;277.98 Function Flat;Paris;2023-03-05;Double;277.88

Slide 12

Slide 12 text

Hotel Price in Brussels • Minimum: 40.13 • Mean: 80.42 • Maximum: 150.20 Expected Result:

Slide 13

Slide 13 text

No content

Slide 14

Slide 14 text

120 90 50 120 150 40 60 80 140

Slide 15

Slide 15 text

No content

Slide 16

Slide 16 text

No content

Slide 17

Slide 17 text

No content

Slide 18

Slide 18 text

No content

Slide 19

Slide 19 text

No content

Slide 20

Slide 20 text

No content

Slide 21

Slide 21 text

INDEX OUT OF BOUNDS?

Slide 22

Slide 22 text

INDEX OUT OF BOUNDS.

Slide 23

Slide 23 text

No content

Slide 24

Slide 24 text

No content

Slide 25

Slide 25 text

No content

Slide 26

Slide 26 text

No content

Slide 27

Slide 27 text

No content

Slide 28

Slide 28 text

CSV is tricky... • Properly handling delimiters is hard. • h e l l o;r u st; f os d e m vs "h e l l o;r u st"; f os d e m • Encodings • Headlines? / No headlines? • etc. • Watch "Stop Using CSV"

Slide 29

Slide 29 text

No content

Slide 30

Slide 30 text

No content

Slide 31

Slide 31 text

No content

Slide 32

Slide 32 text

No content

Slide 33

Slide 33 text

No content

Slide 34

Slide 34 text

No content

Slide 35

Slide 35 text

No content

Slide 36

Slide 36 text

No content

Slide 37

Slide 37 text

No content

Slide 38

Slide 38 text

No content

Slide 39

Slide 39 text

Fighting Ignorance • Embrace Rust's type system • Lean into ownership and borrowing • Learn design patterns • Learn different programming paradigms

Slide 40

Slide 40 text

https://github.com/mre/idiomatic-rust

Slide 41

Slide 41 text

II. Excessive Abstraction

Slide 42

Slide 42 text

Excessive Abstraction • Over-Engineers solutions • Layers indirections • Excessive use of traits, generics, and lifetimes

Slide 43

Slide 43 text

Excessive Abstraction: Red Flags • "FileBuilder, 'a>" • "I might use this again. Let's make it generic!" • "Traits! Traits everywhere!"

Slide 44

Slide 44 text

CSV JSON DATABASE

Slide 45

Slide 45 text

No content

Slide 46

Slide 46 text

No content

Slide 47

Slide 47 text

No content

Slide 48

Slide 48 text

No content

Slide 49

Slide 49 text

FN READ<'A>(&MUT SELF, READ: &'A MUT DYN READ) -> BOX> + 'A>;

Slide 50

Slide 50 text

CSV JSON DATABASE

Slide 51

Slide 51 text

No content

Slide 52

Slide 52 text

THOU SHALT HAVE NO NEED OF IT

Slide 53

Slide 53 text

MACROS COMPILE TIMES

Slide 54

Slide 54 text

Fighting Excessive Abstraction • Keep it simple • Avoid unnecessary complexity • Watch newcomers use your code • Ensure that abstractions add value

Slide 55

Slide 55 text

III. Premature Optimization

Slide 56

Slide 56 text

Premature Optimization • Optimizing code before it's necessary • Using complex data- structures where simple ones would suffice • Neglecting benchmarks

Slide 57

Slide 57 text

Premature Optimization: Red Flags • "Without a lifetime, this needs to be cloned!" • "Let me help the compiler here." • "Ooof, Box is so much overhead!" • "I use BTreeMap because it's faster than HashMap." • "No need to measure if you've got years of experience." • "Zero-copy abstraction" • "Alocaaaaations!!!"

Slide 58

Slide 58 text

clone()

Slide 59

Slide 59 text

No content

Slide 60

Slide 60 text

No content

Slide 61

Slide 61 text

No content

Slide 62

Slide 62 text

No content

Slide 63

Slide 63 text

CSV Parsing (deserialize) String object creation Floating Point operations HashMap access

Slide 64

Slide 64 text

E: Forgetting to run with --release

Slide 65

Slide 65 text

Find actual performance improvements • Measure! • Profile! •s u d o c a r g o f l a m e g r a ph --r e l e a s e • Benchmark! • criterion • divan

Slide 66

Slide 66 text

No content

Slide 67

Slide 67 text

No content

Slide 68

Slide 68 text

No content

Slide 69

Slide 69 text

No content

Slide 70

Slide 70 text

No content

Slide 71

Slide 71 text

34 seconds

Slide 72

Slide 72 text

34 seconds

Slide 73

Slide 73 text

32 seconds

Slide 74

Slide 74 text

No content

Slide 75

Slide 75 text

21 seconds

Slide 76

Slide 76 text

No content

Slide 77

Slide 77 text

13 seconds

Slide 78

Slide 78 text

No content

Slide 79

Slide 79 text

3.5 seconds

Slide 80

Slide 80 text

No content

Slide 81

Slide 81 text

C Developer Rust Performance overhead!

Slide 82

Slide 82 text

No content

Slide 83

Slide 83 text

Fighting Premature Optimization • Measure, don't guess. • Focus on algorithms and data structures, not micro- optimizations • You can get carried away quickly. Be more pragmatic. • Focus on readability and maintainability • Use profiling tools to make informed decisions

Slide 84

Slide 84 text

VI. Omission

Slide 85

Slide 85 text

Omission • Insufficient Testing • Lack of Documentation • Exposing too large APIs • Lack of modularity and encapsulation

Slide 86

Slide 86 text

Omission: Red Flags • "It compiles. My work is done here." • "The code is the documentation." • "Let's just make it all pub." • "I'll refactor that later."

Slide 87

Slide 87 text

No content

Slide 88

Slide 88 text

No content

Slide 89

Slide 89 text

No content

Slide 90

Slide 90 text

No content

Slide 91

Slide 91 text

Fighting Omission • Write more documentation • Write unit tests for your code • Use tools like clippy, cargo udeps, etc. • Set up CI/CD • Create releases • Keep a changelog

Slide 92

Slide 92 text

The Four Horsemen of Bad Rust Code Ignorance Excessive Abstraction Premature Optimization Omission

Slide 93

Slide 93 text

Further reading • RustFest Kiev 2017: Pascal Hertleif - Writing Idiomatic Libraries in Rust • FOSDEM 2018: Matthias Endler - Idiomatic Rust • EuroRust 2023: Nikolai Vazquez - Publishing High-Quality Crates