The Groundhog Day Development Method (HackConf 2019)

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Привет!

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The Books that Every Programmer Must Read (2015)

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The blog post I still have to write :-)

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Teach Yourself Programming in 10+ years (2016)

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Longest talk in the history of conferences!

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Third time is a charm!

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Божидар

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@bbatsov

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emacsredux.com

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metaredux.com

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#7 on the list of top white hackers in Bulgaria!

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Божидар Батсов

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стацковарфлоу

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Expert in cyber security

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Expert in the following programming languages: Unix, Emacs, Perl and Ruby

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The Don Juan of IT in Bulgaria

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Bonus talk

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Personal Finance in 3 minutes

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Disclaimer: That’s not an investment advice. Just some food for thought.

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53 billion BGN in bank deposits.

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Current interest rate on deposits is around 0%.

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Ofﬁcial annual inﬂation in Bulgaria: 3%

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Real annual inﬂation in Bulgaria: Don’t ask!

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Invest some of your savings in a low-cost mutual index fund

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S&P 500

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The average annualized total return for the S&P 500 over the past 90 years is 9.8 percent.

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moneyforsomething.com

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ETFmatic

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The Main Event

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The Groundhog Development Method

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What the f*ck is a groundhog?

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The Groundhog DAY Development Method

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8.0/10

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Life has a funny way of repeating itself…

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Software development has a funny way of repeating itself

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From greenﬁeld to legacy in 2 years

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Case Studies

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A Study in Groundhogs

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Booking Engine

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• 15 year old codebase • A “magniﬁcent” monolith • 500,000+ lines of C++ code • No automated tests • Pretty poor design • make clean install was taking 20-30 minutes • all the classes were preﬁxed with “Lin”

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Let’s rewrite it in Java and that would ﬁx all the problems!

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The (Rewrite) Wasteland

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Big Bang Rewrites Almost Always Fail

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• Stabilize the existing system • Try to isolate some bounded contexts in it (e.g. billing, client-facing functionality, internal functionality) • Start extracting those components one by one (rewriting them if this seems highly beneﬁcial)

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Small improvements over a long period of time really add up!

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Compound Interest Rate

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Content Management System

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• part of a huge multi-purpose Rails monolith (1,5 million lines of code) • the inability to quickly iterate on the CMS functionality impacted directly the revenue of the business • the CMS functionality was relatively simple

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Let’s extract the CMS into a separate application!

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Original estimate - 6 months

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3 years later…

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• the extraction was mostly done, but still not quite • the new project was already considered legacy itself • internal conﬂicts within the team introduced a node.js rendering layer on top of the original CMS app, as some FE devs “disliked” Rails • the development process was still much slower than the goal we set out to achieve

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What’s the moral of the story?

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Any estimate with a 3+ months of a horizon is highly speculative.

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Sometimes WordPress is not a bad thing…

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Don’t become victims of the “Not Invented Here” syndrome

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Quote Streaming Service

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• Implemented in node.js • Solid test coverage • Pretty small codebase (around 5k) • Serious performance issues • Frequent crashes • It was deemed “unﬁxable”

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node.js is the problem

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Let’s rewrite this in Clojure!

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• we’ve encountered serious issues in an upstream Clojure library • there was a lot of internal opposition in the company towards the new service because supposedly “Clojure was too weird” • eventually we rewrote the service back to node.js • no performance issues • no crashes

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Everything is ﬁxable.

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A tool is only as good as the person wielding it.

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The choice of a tech stack should be aligned with the people who are supposed to use it.

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RuboCop

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1,500,000 downloads

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• features that add a lot of complexity get rejected • features that are not aligned with the core goals of the project get rejected • supporting obscure practices get rejected • inclusion of extra runtime dependencies happen extremely rarely • remove features

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Flexible Extension Mechanism

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Simplicity is a design choice.

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nREPL

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800,000 downloads

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•no runtime dependencies •almost no breaking changes •super ﬂexible extension mechanism

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Dependencies are the highway to hell

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Stability is a design choice.

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Hammock time

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Hammock-driven Development https://www.youtube.com/watch?v=f84n5oFoZBc

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Different design approaches for libraries/tools and applications.

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Keep it simple

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Limit external dependencies.

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Be very cautious with adding new features.

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Remove features that are rarely used/didn’t work out.

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Breaking Changes!

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Don’t rewrite anything (big)!

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Say “No!” to hype-driven development

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If you’re always chasing after the next hot technology then you’re never building something valuable.

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Incremental design

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Design

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Legacy is “complex”

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Micro-services are not a silver bullet

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I used to have one big problem, now I have many micro problems.

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Learn how to deal effectively with legacy code

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What’s the best way to learn that ﬁre burns?

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You have to get burned.

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There’s no substitute for experience.

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Felina

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Credits twitter: @bbatsov github: @bbatsov https://metaredux.com https://emacsredux.com HackConf 2019 Soﬁa, Bulgaria 12.10.2019