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Continuous Delivery for Legacy Code 01.02.24 Richard Gross (he/him) Developer Archaeologist Auditor richargh.de/ speakerdeck.com/richargh @arghrich

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Slides by @arghrich What are the properties of low- quality software? 2

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Slides by @arghrich 3 Dave Farely, author of the best-selling book “Continuous Delivery” The Quality of a System is Defined by Our Ability to Change it! Dave Farley @davefarley77

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Slides by @arghrich Bad (legacy) software is software where we no longer have any options 4

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Slides by @arghrich A story of the worst software I have ever and you will never see. 5 And we still got to Continuous Delivery J

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Slides by @arghrich Along comes a customer … 6 Audit Icons by Franziska Haaf binarykitten.de COTS „Apocalypto“ Please Audit Customer Me

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Slides by @arghrich 4M LoC Delivery 7 Audit Excel Webservic e Website Fat Client Jobs Database T-SQL JavaScript VBA C# Asp.NET + C# Classic Asp + VBScript WinForms + C# MIA 5M No Code delivered

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Slides by @arghrich Copy-Based Version ControlTM with production server as origin 8 Audit File tree from actual project

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Slides by @arghrich Cycle Time of 6 months 9 Audit weeks Dev Machine Cp from Prod Develop Compile Don‘t Test Release Cp to Prod 1 hour Bugfixing Return to Start 5 months 6 months

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Slides by @arghrich Too much to fix 10 Audit Icon by Franziska Haaf binarykitten.de „Interesting“ Deployment 15 years of Uncontrolled growth Horrible Cycle Time No Tests Conflated Logic, UI & SQL Not Versioned & Doesn‘t Compile

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Slides by @arghrich 11 Icons by Franziska Haaf binarykitten.de COTS „Apocalypto“ In-house „Fenix“ Buy I‘ll Customer Money

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Slides by @arghrich 12 Icons by Franziska Haaf binarykitten.de In-house „Fenix“ Please Fix Me Customer

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Oh Boy

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Ken Mugrage @kmugrage Legacy Code is code that’s too scary to update and too profitable to delete. It‘s not CD if you can‘t deploy to production right now Dylan Beattie @dylanbeattie Slides by @arghrich 14

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Slides by @arghrich Can we deploy this to production right now? Nope 15

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16 Slides by @arghrich Not Versioned & Doesn‘t Compile Icon by Franziska Haaf binarykitten.de 16

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• Code • Configuration • Deployment scripts • Infrastructure Provisioning • Alerting • Monitoring • Documentation • Onboarding.sh Scripts • … 17 Put everything into version control Slides by @arghrich 17 Git

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Slides by @arghrich Establish a Pipeline 18 Commit Stage Compile Git

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Slides by @arghrich Versioned & Automated Compile „Interesting“ Deployment 19

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Slides by @arghrich Scripts to Provision Infrastructure Same but parameterized Scripts for TST, STG and PRD • Machine • Web Server • Application Server • Database • Email Server • FTP Server • Pipeline Server 20 Phoenix Infra: With one click we can (re)create any infrastructure Gives us

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Slides by @arghrich Deploy via Pipeline to Test Env 21 Commit Stage Compile Git Deploy To TST (Cont.) STG (Click) Smoke Test

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Slides by @arghrich Can we deploy this to production right now? We have a button to do it, but do we want to? 22

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Automated Deployment Slides by @arghrich Versioned & Automated Compile 15 years of Uncontrolled growth

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Slides by @arghrich Don’t “Fix everything at once, mindset”TM 24

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Slides by @arghrich Do the “Hotspot Mindset”TM 25

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Slides by @arghrich Finding Hotspots 26

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Art by Zaufishan Slides by @arghrich 27

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Visualize metrics with CodeCharta buildings SomeService.cs Lines of code Complexity number of authors Icons by Fontawesome Open-Source Tool CodeCharta: https://maibornwolff.github.io/codecharta/ Slides by @arghrich 28

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Find potential hotspots Open-Source Tool CodeCharta: https://maibornwolff.github.io/codecharta/ Slides by @arghrich 29 Lot‘s of code, very complex, and everyone has to change it

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Slides by @arghrich No tool to rule them all 30 Shamelessly putting CodeCharta first 1 Quality Views by Colin Breck Continuously Periodically Structure101 SonarQube CodeCharta CodeScene ArchUnit TSArch SonarArchitec t Quality Views 1

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Slides by @arghrich 31 1 By Matthias Verraes 2 Graphana Graphs + Push Gateway Photo by Pixabay from Pexels Count Fixed Windows 2 Three Post-it‘s To Refactor 1 Slides by @arghrich

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Versioned & Automated Compile Automated Deployment We know what to focus on No Tests Conflated Logic, UI & SQL

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Slides by @arghrich Start with tests for critical use cases and hotspots • ~10 E2E Tests For critical use cases • DB-Integration Tests For direct-db-access hotspots that you will refactor • Unit tests (should give 80% confidence) For refactored hotspots For no-direct-db-access hotspots For new code 33

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Slides by @arghrich Categorization test1: Write Tests for code that you don’t understand 34 1 Also called approval or golden master test. 2 Put system in a known (database) state is also an input. 3 Log messages you add are also an output. vX - redesigned v1 - legacy Input for UI/API/DB 2 Output 3 Output 3 Continuous Compare

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Slides by @arghrich Understand Coupling and Cohesion High Coupling Low Cohesion Low Coupling High Cohesion 35 Unknown source

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Slides by @arghrich Uncouple your Code 36 Delete Obsolete (unreachable or unused) Code Categorization Test, then Refactor Code Sprout new tested Code Break Dependencies (Seams) Strangler Fig Unfixable code Feature Flag Legacy Code Write ArchUnit Tests

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Slides by @arghrich Can we deploy this to production right now? Hmm, it’s somewhat tested but can we really be sure nothing breaks in production? 37

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38 Automated Deployment Slides by @arghrich Versioned & Automated Compile Seperated Logic, UI & SQL In Hotspots Critical Use Case Tests Growing Unit Tests Unit tested new code We know what to focus on Horrible Cycle Time

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Slides by @arghrich Do Monitor in Production 39

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Slides by @arghrich RED Metrics 40 1 https://thenewstack.io/monitoring-microservices-red-method/ Community Dashboard https://community.grafana.com/t/how-can-i-configure-red-dashboard/69885 R -> Request Rate E -> Errors / second D -> Duration per request

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Slides by @arghrich New Cycle Time, without bug-cycle 41 Slide adapted from Dave Farley Commit Stage Compile Unit Test Lint Security Docker Release Git Monitor Logs Events Metrics Alerts Automated Performance testing 20 min Deploy To TST (Cont.) STG (Click) Smoke Test <1 min Manual Testing 30 min Automated Acceptance Testing User Acceptance Test DB-Integration Test 20 min 5 min 60 min

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Slides by @arghrich Can we deploy this to production right now? Yes. Depending on where we make the change, even within 30min. 43

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Slides by @arghrich But there is still a problem… 44

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Slides by @arghrich How did the previous developers get here? 45

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Slides by @arghrich Healthy Software 46 Ideas Product Process Mindset Predicts

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Slides by @arghrich GIGO 47 Ideas Product Process Mindset Predicts

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Slides by @arghrich A Feature Factory helps no one 48 https://cutlefish.substack.com/p/tbm-4952-your-calendar-your-priorities

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Slides by @arghrich 49 Henrik Kniberg @henrikkniberg Culture is the sum of everyone's attitude and actions, so model the behaviour you want to see! Observe behavior: • Who does the management promote? • Is there fear of failure? • Is quality appreciated or story points or …? • What is the delivery „process“? • Is there some kind of learning exchange?

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Slides by @arghrich Make the desired behavior … 50 Obvious • Define Principles together • Shared purpose Attractive • Reduce (time) pressure • (Refactoring) score Atomic Habits 4 Laws of behavior change Easy • Tech-coach • Reduce friction Satisfying • Pair up • Never break the chain (twice)

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Slides by @arghrich CD is a change in mindset 51

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Slides by @arghrich CD = Working in a way that software is always in a releasable state It’s not about the tools, even though they are getting better all the time 52

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Slides by @arghrich Thanks 53 Developer Richard Gross (he/him) Archaeologist Auditor richargh.de/ speakerdeck.com/richargh @arghrich Works for maibornwolff.de/ Tailored Software by People who Care. DE TN ES

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Slides by @arghrich Backup 55

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Slides by @arghrich 10 customer installations 57 Frobozz Co. Oceanic Airlines … Umbrella Corp Soylent Corp

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Slides by @arghrich And also 10 separate codebases 58 … Oceanic Airlines Soylent Corp Frobozz Co. Umbrella Corp Similar C/P Copy/ Paste Feature Copy/Paste

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Slides by @arghrich 10 codebases And 10 database schemata 59 Similar Similar

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Slides by @arghrich Our Legacy CD Principles • Build quality in • Focus on current tree, not on the forest • Tackle fear head on • Focus on reducing batch size • Decouple Deployment and Release • Computers perform repetitive tasks, people solve problems 60 CD Principles by Jez Humble Four Principles of Low-Risk Software Releases by Jez Humble

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Slides by @arghrich Our branching strategy • Don‘t Branch • Don‘t Even Branch • Branch and you’re screwed • Never Branch to Refactor • Branches indicate Ci =Continuous Isolation 61

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Slides by @arghrich The True Cost of Rewrites 62 Original Article by Doug Bradbury The True Cost of Rewrites Features Releases over time Catch Up Missing Features Sub-Par Parity Enhancements Planned Rewrite Actual Features Undiscovered Scope Old App Adoption