Strangle Your Legacy Code

#### <a href="https://twitter.com/hashtag/softwerkskammer">#softwerkskammer</a>

[schmonz.com/talk<br />/2018-muenchen](https://schmonz.com/talk/2018-muenchen/)
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.left-column[
<a href="https://www.meetup.com/munich-software-craft-community/"><img src="./150x150-logo.png" width="150" height="148" alt="Munich Software Craft Community" class="img" /></a>
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#### <a href="https://twitter.com/hashtag/softwerkskammer">#softwerkskammer</a>

[schmonz.com/talk<br />/2018-muenchen](https://schmonz.com/talk/2018-muenchen/)
]

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# Strangle Your Legacy Code

## Amitai Schleier

### 2018/08/30

???

1. Press 'C' to clone and move it to projector
2. Press 'P' to show these here presenter notes

### 90 minutes or whatever

Given an ancient codebase that makes refactoring risky and expensive, how do you clear a path to continued delivery? The old wisdom says the best time to plant a tree was 20 years ago, and the next best time is today. But if you already have a gnarled old source tree, preserve your software investment by planting a Strangler: a pattern for reaping continuous value from your existing system while growing new functionality alongside it.

We'll take a quick look at a Strangler, demonstrate the basics of Mob Programming, then split into small groups to test-drive new features into the system. You'll leave with a powerful strategy for extending the useful life of working, valuable software -- *especially* when it's hard to change -- and with a free bonus development practice to accelerate your team's learning. For a limited time only!

### How to introduce the problem

- Responsible for production email service
- Keep having to extend it (business, regulatory requirements)
- Look at ofmipd code
- On my 20% time, I had an idea for how to make development easier, cheaper, safer
- Run ofmipd
- Run ofmipd behind env AUTHUP_USER=tim fixsmtpio
- Note the differences?
- We're going to do the same kind of thing, in Python
- Let's run it and say "WORD UP" to the server
- See how that works
- Okay, let's make a new test pass

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## 1. Introduction to Strangler

## 2. Develop in a real Strangler

## 3. Collect learnings
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## Is there one for this meetup?

## Remind ourselves how we want to behave

## Like TDD, declaring our intentions helps us live up to them
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> "One of the natural wonders of [the Queensland coast] are the huge
> strangler vines. They seed in the upper branches of a fig tree and
> gradually work their way down the tree until they root in the soil.
> Over many years they grow into fantastic and beautiful shapes,
> meanwhile strangling and killing the tree that was their host."  
> --[Martin Fowler](https://www.martinfowler.com/bliki/StranglerFigApplication.html)
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## Alternative to Big Rewrite

## Mitigates risk to business

## Likely reduces cost to business
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## We're responsible for AcmeCo's email service

## C code from 1998

## We like it, and have invested a lot in it

## But each new feature is expensive to build
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## Mob Programming:

### Whole team, same problem, same computer

### Think out loud, together

### Driver, Navigator, rotate

## [github.com/schmonz/smtp-strangler](https://github.com/schmonz/smtp-strangler/tree/munich-software-craft)
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- Keyboards and mice always get in someone's way
- Python is sort of readable to most devs
- These tests aren't precise enough for good TDD
- Automated integration tests would give more safety
- Mob gives more ideas about how the code might work
- Mob gets stuck less, is more fun
- Running timer adds a feeling of time pressure
- Short enough timer to not feel scary
- Both Driver (just listen) and Navigator (get ideas for your teammates) are safe
- When driving, it's hard to stop thinking
- Strangler: move incrementally to microservices, instrument features in use
- Strangler migration: duplicate functionality until we trust new impl
- Many tradeoffs in choosing to mob: social dynamics, tech stack, willingness
]

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- [SMTP Strangler](https://github.com/schmonz/smtp-strangler) (github.com)
- [Strangler Application](https://www.martinfowler.com/bliki/StranglerApplication.html) (martinfowler.com)
- [Mob Programming Guidebook](https://leanpub.com/mobprogrammingguidebook) (leanpub.com)
- [Mob Programming RPG](https://github.com/willemlarsen/mobprogrammingrpg) (github.com)
- [Coding Tour Summer 2018](https://schmonz.com/talk/2018-tour/) (schmonz.com)
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## <a href="https://agilein3minut.es/">agilein3minut.es</a>

> "Before Agile in 3 Minutes, I couldn't get my team to have a
> conversation about important topics. Now I have to timebox it."

- <a href="https://agilein3minut.es/8">8: Care</a>
- <a href="https://agilein3minut.es/32">32: Mob</a>
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## [leanpub.com/agilein3minutes<br />/c/mscc](https://leanpub.com/agilein3minutes/c/mscc)

The simplest _essays_ that could possibly work.
Lowest allowable price on Leanpub, today!
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# Strangle Your Legacy Code

## Amitai Schleier

## [latentagility.com](https://latentagility.com)