The Complexity Trap: Think Before You Leap

Recently, many people in the functional programming community, and specifically in the Scala community, seem to follow the trend of solving their programming problems with more and more fancy abstractions and techniques. If in doubt, we throw a monad at the problem, and if that’s not good enough, we’ll make it free. Naturally, to top it off, we have to sprinkle the whole thing with some type-level programming, because this is common courtesy these days.
LAMBDA WORLD 2018, Cádiz

In this talk I want to challenge some of the fundamental assumptions of how we think and work. With all our sophisticated engineering, are we actually solving the right problems? Are we rushing towards technologically exciting solutions too quickly? How much of the complexity in our software is inherent in the problem domain, and how much of it is of our own making? We may have honorable intentions, but do our solutions come at an acceptable price? Maybe it’s time to slow down, think about what the problems we have to solve actually are, and how to do so in the simplest way possible.

Transcript

1. LAMBDA WORLD CADIZ 2018 The Complexity Trap: Think Before You Leap Daniel Westheide @kaffeecoder
2. What is this talk about? Photo by Domenico Gentile on Unsplash
3. Agenda • What is complexity? • The complexity trap & how to escape it – Neglecting the costs – Embracing industry standards – Maximum zoom • Conclusions
4. complex Photo by drmaket lab on Unsplash
5. simple Photo by Johny Goerend on Unsplash
6. Types of complexity • Essential complexity • Accidental complexity
7. Metrics or it didn‘t happen! // Cyclomatic complexity = 1 def squared(x: Int): Int = x * x // Cyclomatic complexity = 2 def max(x: Int, y: Int): Int = if (x >= y) x else y
8. Cognitive complexity public static int sumOfPrimes(int max) { int total = 0; OUT: for (int i = 1; i <= max; ++i) { for (int j = 2; j < i; ++j) { if (i % j == 0) { continue OUT; } } total += i; } return total; } def sumOfPrimes(max: Int): Int = Stream .range(1, max + 1) .filter(i => (2 until i).forall(j => i % j != 0)) .sum Java version taken from: https://blog.sonarsource.com/cognitive-complexity-because-testability-understandability
9. Miller‘s law Photo by juan pablo rodriguez on Unsplash
10. Abstraction Photo by Jaciel Melnik on Unsplash
11. The sound of poison has gone off Our traps aren't malleable, beware! No dogma or deterrent can dissuade us from our torment path Said path has run nigh on eight years Dark skills in trade, we hone and sharpen arrow blade The trap is laid While we await and wait and wait Laying Traps Crippled Black Phoenix 2012 Photo by Mario Azzi on Unsplash
12. Neglecting the costs Photo by Marissa Rodriguez on Unsplash
13. Example: Scrapping your boilerplate with too much passion
14. Choose your poison Photo by Kylli Kittus on Unsplash
15. Embracing industry standards Photo by Samuel Zeller on Unsplash
16. Embracing industry standards the latest fad Photo by Shawn McKay on Unsplash
17. Example: Abstracting over monads. Everywhere. All the time.
18. Use cases • Library development • Need for multiple interpreters in your program
19. Uses in application development def showArticlePage(id: Long): Task[ArticlePage] = for { article <- fetchArticle(id) comments <- if (article.commentingAllowed) fetchComments(id) else Task.now(Seq.empty) } yield ArticlePage(article, comments) def showArticlePage(id: Long): Free[Effect, ArticlePage] = for { article <- fetchArticle(id) comments <- if (article.commentingAllowed) fetchComments(id) else Free.pure[Effect, Seq[Comment]](Seq.empty) } yield ArticlePage(article, comments)
20. The costs of abstraction
21. Foregoing abstraction Photo by Markus Spiske on Unsplash
22. Functional core, imperative shell Photo by Kelly Sikkema on Unsplash
23. Functional core, imperative shell // imperative shell: def showArticlePage(id: Long): Task[ArticlePage] = for { article <- fetchArticle(id) comments <- commentingAllowed(article) .fold(_ => Task.now(Seq.empty), _ => fetchComments(id)) } yield ArticlePage(article, comments) // functional core: def commentingAllowed(article: Article): Either[String, Unit] = { if (article.commentingAllowed) Right(()) else Left("Commenting not allowed") }
24. Discourse • Focuses on how instead of why (or why not) • Emphasis on more and more advanced techniques
25. Let’s write more about trade-offs
26. Let’s write more about boring solutions
27. Maximum zoom Photo by Drew Graham on Unsplash
28. Example: Microservices with frontend service
29. We jump towards technological solutions too quickly
30. aim42 • Architecture improvement method • Iteratively in three phases: – Analyse – Evaluate – Improve • https://aim42.org/
31. Root cause analysis
32. … applied to the latency problem • Why is our overall request latency so high? • Why do we need to make so many requests? • Why are our microservices designed around a single entity? • What if … ?
33. What if … ?
34. … applied to the JSON codecs • Why do we provide a JSON API? • Why do we have a single page app?
35. What if … • we did server-side rendering of HTML? – No JSON API – No duplicated business logic – Much simpler frontend JS code https://medium.com/@jmanrubia/escaping-the-spa-rabbit-hole-with-turbolinks-903f942bf52c
36. We love (functional) programming too much
37. Coding ~ Comfort zone Photo by Marcos Gabarda on Unsplash
38. What does it mean to be a software developer?
39. Conclusions • Leave your programmer comfort zone • Consider costs • Talk about trade-offs • Don’t ignore boring solutions • Slow down & stop meddling with symptoms
40. Thanks for your attention! Questions? Daniel Westheide @kaffeecoder