Top Legacy Sins - Speaker Deck

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Top Legacy Sins Eberhard Wolff Fellow @ewolff

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http://microservices-buch.de/ http://microservices-book.com/

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What should a Software Architect do?

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Create a Proper Architecture.

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Create a Proper Architecture. Agree??

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I’m a Software Architect. But I’m not doing architecture. !

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How important is Software Architecture?

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Why would we care about Software Architecture?

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Software Architecture =Structure

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Architecture Goals: Quality > All kinds of quality > Performance > Security > … > Focus of this presentation: Changeability > Architects must understand customers & priority

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Architects must understand customer

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Software Architecture Set of structures comprise software elements, relations among them, and properties of both.

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Why? > Can work on modules in isolation > Can work on collaboration of modules > Fits in my head Dan North

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Does He Care?

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Why? Great Architecture Software Easy to change High productivity Low Cost

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He Cares €

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Why? Great Architecture Software Easy to change High productivity Low Cost

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What He Cares About Great Architecture Software Easy to change High productivity Low Cost

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Is architecture the only factor for changeability?

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What is the best thing we can have in a legacy code?

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Great architecture or automated tests?

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No Automated Tests > No way to find bugs > Changes almost impossible > Legacy code = code without tests > Michael Feathers Working Effectively with Legacy Code

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Let’s add some automated UI tests

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Automated UI Tests > Easy to implement > Exactly what testers do manually > Easy to understand for customers > Test business processes > Safety net

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Unit Tests or automated UI tests?

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Many UI Tests Worse > Fragile: Changes to UI break test > Business meaning of tests easily lost > Takes long > Often not reproducible

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Automated UI Tests Automated Integration Tests Unit Tests Manual Tests

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Automated UI Tests Automated Integration Tests Unit Tests Manual Tests

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Slow Unreliable Expensive

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Alternatives to automated UI tests?

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Textueller Akzeptanztest

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Szenario > Möglicher Ablauf in einer Story > Standardisierte Bestandteile: > Gegeben... (Kontext) > Wenn... (Ereignis) > Dann... (erwartetes Ergebnis)

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Szenario: Beispiel Szenario: Kunde registriert sich erfolgreich Kontext Ereignis Erwartetes Ergebnis Erwartetes Ergebnis Gegeben ein neuer Kunde mit EMail [email protected] Vorname Eberhard Name Wolff Wenn der Kunde sich registriert Dann sollte ein Kunde mit der EMail [email protected] existieren Und es sollte kein Fehler gemeldet werden

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RegistrationService registrationService; // Initialisierung RegistrationService // ausgelassen private User kunde; private boolean fehler = false; @Given("ein neuer Kunde mit "+ "EMail $email Vorname $vorname"+ " Name $name") public void gegebenKunde(String email, String vorname, String name) { kunde = new User(vorname, name, email); }

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@When("der Kunde sich registriert") public void registerKunde() { try { registrationService.register(kunde); } catch (IllegalArgumentException ex) { fehler = true; } } @Then("sollte ein Kunde mit der EMail $email existieren") public void existiert(String email) { assertNotNull(registrationService.getByEMail(email)); } @Then("es sollte kein Fehler gemeldet werden") public void keinFehler() { assertFalse(fehler); } }

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Test is about handling risk

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Tests for Risks > Algorithm / calculation wrong: Unit test > System failures: Unit tests > Wiring / collaboration: Integration tests > Business process: Integration test > UI: UI test

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Example: User Registration > Unit test Validations Database failure > Integration test Process > UI test Everything shown?

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Not Tested > UI won’t test validation > …or algorithms > …or the process > Risks handled elsewhere

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Automated UI Tests Automated Integration Tests Unit Tests Manual Tests

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Automated UI Tests. Automated Integration Tests Unit Tests Manual Tests Test Pyramid

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Test Pyramid instead of Automated UI Tests

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Great architecture or fast & easy deployment?

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Deployment > Manual deployment is error prone > Slow deployment > Lots of code developed but not deployed > i.e. more lean waste > Slow feedback > Slow time to recovery

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Leseprobe: http://bit.ly/CD-Buch

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Continuous Delivery: Build Pipeline Commit Stage Automated Acceptance Testing Automated Capacity Testing Manual Explorative Testing Release

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Continuous Delivery > Testing > + automated deployment > Testing: reduce probability of errors > Automated deployment: better mean time to repair

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Continuous Delivery > Make software easier to change > & deploy > Reliable and reproducible tests > Automated deployed > Fast & reliable

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What is a great architecture?

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UI Logic Database

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Is Three Tier a great architecture?

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Three Tier > Actually layer: no distribution > By technology > Layers can be replaced > Layers can be developed independently

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Do you replace e.g. the persistence layer?

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Is it really simple to add e.g. mobile clients?

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A better reason: Fits in my head.

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Redo the order processing!

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Add feature to the registration! Can we change the persistence technology instead? Please?

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What is a persistence technology??

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Registration Order Billing UI Logic

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Architecture > Should support changes > …with business value > Needs to model the domain > Hard to get right > Architect needs to understand the domain

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Is a great architecture free of cyclic dependencies?

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A B A depends on B Changes to B influence A

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A B A depends on B Changes to B influence A B depends on A Changes to A influence B In fact one component Should be two components

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Is a great architecture free of cyclic dependencies?

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Cyclic dependencies: Architects’ Mortal Sin

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A B A B 42 2 200

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Other Architecture Metrics > High cohesion > Elements of a module should belong together > Low coupling > Modules should not depend on each other

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Great Architecture > Don’t overrate cyclic dependencies! > Consider other metrics > Architecture by domain

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The worst legacy problems?

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The project has a lot of cyclic dependencies! I know. …but that doesn’t cause a lot of trouble

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Architects must understand customer & his quality demands

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Quality > Changeability > Performance > Security > …

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No two projects are alike.

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No general rules.

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Sorry!

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Software Easy to change Automated tests Test pyramid Fast & easy deployment Great Architecture No cyclic dependencies Low coupling High cohesion

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What should a Software Architect do?

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Create a Proper Architecture.

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Create a Proper Architecture.

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I’m a Software Architect. But I’m not doing architecture. There is more to changeable software than architecture.

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Thank You! @ewolff