Strangle Your Legacy Code

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

[schmonz.com/talk<br />/2019-nyc-february](https://schmonz.com/talk/2019-nyc-february/)
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### <a href="https://twitter.com/schmonz">@schmonz</a>

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

[schmonz.com/talk<br />/2019-nyc-february](https://schmonz.com/talk/2019-nyc-february/)
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# Strangle Your Legacy Code

## Amitai Schleier

???

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

#### 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:

1. Whole team, same problem, same computer

2. Think out loud, together

3. Driver, Navigator, rotate
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- Full rewrites don't _always_ fail
- Your legacy system is more complex than SMTP
- Limit interactions between Strangler and Strangled
- When to choose Strangler?
    - Incremental rehab isn't worth the cost
    - Goal: eventually decommission existing system
    - Or: maybe we will, maybe we won't!
    - Or: instrument actual usage, then decide
    - Might reflect org's bias for action (try something)
- Biggest risk: deploying the initial Strangler, hoping nothing changes
- Mobbing:
    - Knowledge better shared and retained
    - Team and org issues magnified
    - Peer pressure to cut corners, perhaps, but also shared feedback about consequences
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- [SMTP Strangler](https://github.com/schmonz/smtp-strangler/tree/ny-xpagile) (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/nyxp19](https://leanpub.com/agilein3minutes/c/nyxp19)

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

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