BIG REWRITE STRIKES AGAIN Sabrina Leandro @saleandro The Lead Developer UK 2017

Lessons from Big rewrite projects

BIG REWRITE STRIKES AGAIN

This talk • The problem • How to start it • How to run it • How to finish it • How to not need it again!

The problem Stop me if you think you’ve heard this one before

Software Entropy

No content

How to start it

•Is it the right time? •Is it the right reason?

Product discovery Is it the right time?

Product discovery Product delivery Is it the right time?

Is it the right time? Yes, if the product has a clear business value today.

What difference does it make? Is it the right reason?

•Do you have a business case?
 


•Do you have a business case? •Can you explain it to anyone in your organisation?

Is it the right reason? Yes, if there’s one clear business case.

PLEASE PLEASE PLEASE Let me get what I want

Have one clear business case How to sell it

How to sell it Show what a great new world 
 it will be!

How to sell it Find allies outside of your team

Make the pain visible How to sell it

How to sell it Do Repeat Yourself

How to sell it Do Repeat Yourself Do Repeat Yourself

How to run it

Technical vision and strategy Now The future!

Now The future! Technical vision and strategy

Technical approaches

Now Bright future! Team 2: Building new application Rewrite from scratch Legacy application Team 1: Maintaining legacy application New New application New application VALUE! Legacy application Legacy application

Now Bright future! Team 2: Building new application Rewrite from scratch Legacy application Team 1: Maintaining legacy application New New application New application VALUE! Legacy application Legacy application Legacy application

The strangler application

Now Bright future! Team 1: Maintaining legacy and building new application New application Rewrite using strangler approach

Now Bright future! Team 1: Maintaining legacy and building new application New application VALUE! Rewrite using strangler approach

“ Deleting is faster than rewriting.

Bones Muscle Fat Cut features to move faster

“ If we were starting over, what would we build today, knowing what we know now?

1) Find the biggest blocker 2) Remove it completely 3) Repeat What to do first?

During the project

How to run it Show internal progress

How to run it Celebrate your successes!

No content

No content

No content

No content

That joke isn’t funny anymore… How to run it Do Repeat Yourself, again

How to finish it I started something I couldn’t finish

These things 
 take time How to finish it

How to not need it again

Software Entropy

How to not need it again Make the cost visible

No content

DELETE CODE FEATURES PRODUCTS

“ If we were starting over, what would we build today, knowing what we know now?

How to not need it again Make it part of your day-to-day

“ A refactor a day keeps the rewrite away!

How to not need it again Get used to inconsistencies

How to not need it again Promote a culture of collaboration

Technical migrations Continuously deliver value Delete what’s not valuable One business goal

Sustainable Software Make maintenance cost visible Learn and collaborate Refactor a little bit and often

Bigmouth Strikes Again This Charming Man Stop Me If You Think You’ve Heard This One Before What Difference Does It Make? Please, Please, Please, Let Me Get What I Want That Joke Isn’t Funny Anymore I Started Something I Couldn’t Finish These Things Take Time Sheila Take A Bow Thanks! Sabrina, take a bow… [email protected] @saleandro

References Songkick.com rewrite • https://devblog.songkick.com/the-path-to-soa-d986a18d4a8b • https://devblog.songkick.com/our-object-based-rails-frontend-3e2ddc048d12 • https://www.youtube.com/watch?v=-VEf8j6aGMk • https://www.martinfowler.com/bliki/StranglerApplication.html Celebrate your successes • https://medium.com/@Songkick/gamify-your-product-team-to-power-level-9000-261e9fceaa22 Hoarders metaphor / Liveable code • https://twitter.com/sarahmei/status/783115752794492928 • https://www.youtube.com/watch?v=mz3l_oEA2cU • https://twitter.com/kentbeck/status/856537528886673408 Product discovery and product delivery • http://jpattonassociates.com/dual-track-development/ • https://martinfowler.com/bliki/DesignStaminaHypothesis.html • https://www.facebook.com/notes/kent-beck/teams-in-3x/1244519748914220/

References Make the cost visible • http://codemanship.co.uk/parlezuml/blog/?postid=1433 • http://blogs.msdn.com/b/elee/archive/2009/03/11/source-code-is-a-liability-not-an- asset.aspx Make it part of your day-to-day • https://martinfowler.com/bliki/OpportunisticRefactoring.html • http://ronjeffries.com/xprog/articles/refactoring-not-on-the-backlog/ • http://firstround.com/review/forget-technical-debt-heres-how-to-build-technical-wealth/ • https://www.infoq.com/presentations/microservices-replaceability-consistency • https://www.sandimetz.com/blog/2017/6/1/the-half-life-of-code • https://www.infoq.com/presentations/remove-unneeded-code Playlist :) • https://open.spotify.com/user/saleandro/playlist/6i3RVHtys4djlYlLLGZc26