Taming Agile Architecture

Michael Haeuslmann @

Disclaimer

The opinions expressed in this presentation and on the following slides are solely those of the presenter and not necessarily those of TNG Technology Consulting.

"Individuals and interactions over processes and tools..."

- Agile Manifesto

Let's be agile, lets interact!

Agenda

Agile/Architecture Myths

Practicing Agile Architecture

Why do we even talk about this?

“The word 'agile' has been subverted to the point where it is effectively meaningless, and what passes for an agile community seems to be largely an arena for consultants and vendors to hawk services and products.”

- Dave Thomas

The Fine Art of Baloney Detection

"The Demon-Haunted World: Science as a Candle in the Dark" - Carl Sagan

there must be independent confirmation of "facts"
arguments from authorities carry little weight
try not to get overly attached to a hypothesis, just because it's yours
...

Agile!

The Good, the Hype and the Ugly

Bertrand Meyer

"One Hacker Way"

by Erik Meijer

Agile Manifesto

Individuals and interactions
over processes and tools
Working software
over comprehensive documentation
Customer collaboration
over contract negotiation
Responding to change
over following a plan

That is, while there is value in the items on
the right, we value the items on the left more.

Myth #1

Agile means no documentation

Myth #2

Agile means no architecture

Myth #3

Good coding practices lead to good architecture

Myth #4

Agile means everything is easy to change

(even architecture)

Myth #5

Scrum === Agile

Myth #6

We're agile because ...

... we're using Jira
... we're doing Standups
... we use microservices
... we're using DDD

Architecture

"Software architecture refers to the high level structures of a software system, the discipline of creating such structures, and the documentation of these structures."

- Wikipedia

Architecture

"[Architecture] is the stuff that's hard to change"

"Architecture is not all about diagrams; it's about promoting collaboration and communication of the critical parts of the system."

- Martin Fowler

Problems with traditional architecture

ivory-tower architecture
making unnecessary decisions too early
architect not part of the team
architect not accountable

Architecture is the stuff that's hard to change?

So how do we come up with agile architecture?

Gather all known requirements

Identify nouns and verbs

Whiteboard Architecture

Class-Responsibility-Collaboration Cards (CRC)

Class

Responsibility

Collaboration

"Factor your system so that artifacts that change at similar rates are together."

- Foote & Yoder

Test your architecture

Go crazy

native support for Arabic users
Bitcoin check-out
record user interaction for audits
make all user actions undoable
create native apps for iOS, Android, ...
add offline support

Design Decisions

as little as possible, as much as needed
think big, act small
KISS - Keep It Simple, Stupid
YAGNIY - You ain't gonna need it (yet)

Architectural Decisions

"Beware of people who love to think about abstractions more than coding software." - Steve Green

Microservices

"Beware of the distributed monolith connected via a database" @lornajane #CraftConf meetup pic.twitter.com/SvsxykXiQY
— Daniel Bryant (@danielbryantuk) April 26, 2017

Fallacies of distributed computing

The network is reliable.
Latency is zero.
Bandwidth is infinite.
The network is secure.
Topology doesn't change.
There is one administrator.
Transport cost is zero.
The network is homogeneous.

You are not Netflix.

You're probably fine starting out with a Monolith.

Think in modules/services

but

distribute over the network only if absolutely necessary

Domain Driven Design

vs.

Domain Centered

Domain-Driven Design

Domain Driven Design

Tackling Complexity in the Heart of Software
introduces overhead
requires knowledge of existing architectural patterns
not a one-size-fits-all approach

Same thing goes for Event Sourcing

Everyday Architecture

sprint 0, -1, ... for big projects
architecture backlog items
code reviews also from a 30.000 foot view
retrospectices, ...
in small/medium projects, everyone is the architect

"An architect's value is inversely proportional to the number of decisions she/he makes."
- Martin Fowler

Bring your Architecture and Documentation back to life

Revive your Documentation

Single Source of Truth
Behavior Driven Development
Word < Wiki / Confluence < Markdown/TeX + Git
Extract information (e.g. screenshots from acceptance tests, architecture from code, ...)
Broken window theory (markdown linters, grammar check e.g. write-good, check changelog, ...)

Revive your Architecture

detects even the sneakiest dependencies
generates dependency visualizations
hackable (grep, sed, awk, ...)
supports PHP 5.2 to 7.1

Features

Text Output
For quick feedback, debugging, UNIX pipes etc.

Various Visualisations (UML & DSM & dot)
Detailed dependency & architectural analysis

(Metrics)

How does it work?

parses PHP code
builds an abstract representation (AST)
detects dependencies for all classes
applies filters and transformers
writes output as text, pictures e.g.


λ wget http://phar.dephpend.com/dephpend.phar -O ~/bin/dephpend
λ dephpend --help
      _      _____  _    _ _____               _
     | |    |  __ \| |  | |  __ \             | |
   __| | ___| |__) | |__| | |__) |__ _ __   __| |
  / _` |/ _ \  ___/|  __  |  ___/ _ \ _ \ / _` |
 | (_| |  __/ |    | |  | | |  |  __/ | | | (_| |
  \__,_|\___|_|    |_|  |_|_|   \___|_| |_|\__,_| version 0.4

 Usage: ...
λ dephpend text ~/workspace/dephpend/src
Mihaeu\PhpDependencies\Util\AbstractMap --> Mihaeu\PhpDependencies\Util\Collection
Mihaeu\PhpDependencies\Util\DI --> Mihaeu\PhpDependencies\Analyser\Analyser
...


<?php

$cmd = shell_exec('dephpend text src --no-classes');
$constraints = [
    'Model.* --> .*View',
    'View.*  --> .*Model',
];
$regex = '/('.implode(')|(', $constraints).')/x';

if (preg_match($regex, $cmd)) {
    echo 'Architecture violation'.PHP_EOL;
    exit(1);
}

ArchUnit

@ArchTest
public static final ArchRule layers_are_respected = layeredArchitecture()
        .layer("Root").definedBy("com.tngtech.archunit")
        .layer("Base").definedBy("com.tngtech.archunit.base..")
        .layer("Core").definedBy("com.tngtech.archunit.core..")
        .layer("Lang").definedBy("com.tngtech.archunit.lang..")
        .layer("Library").definedBy("com.tngtech.archunit.library..")
        .layer("JUnit").definedBy("com.tngtech.archunit.junit..")

        .whereLayer("JUnit").mayNotBeAccessedByAnyLayer()
        .whereLayer("Library").mayOnlyBeAccessedByLayers("JUnit")
        .whereLayer("Lang").mayOnlyBeAccessedByLayers("Library", "JUnit")
        .whereLayer("Core").mayOnlyBeAccessedByLayers("Lang", "Library", "JUnit")
        .whereLayer("Base").mayOnlyBeAccessedByLayers("Root", "Core", "Lang", "Library", "JUnit");

Escaping Dependency Hell

Summary

Use your baloney detection kit
be wary of agile "processes"
let's all be architects
fail fast and learn rapidly
live architecture
validate your architecture decisions
revive your documentation

Questions?

Michael Haeuslmann

@michaelhaeu

https://github.com/mihaeu

Feedback?

Books

Clean Architecture by Robert C. Martin
Agile! - The Good, the Hype and the Ugly by Bertrand Meyer
The Pragmatic Programmer by Andrew Hunt, David Thomas
Extreme Programming Explained by Kent Beck, Cynthia Andres
...

Sources

http://www.denofgeek.us/sites/denofgeekus/files/6/25/frankenstein-1931.jpg
https://www.slideshare.net/gahlawatanju21/agile-reluctancy-in-india-anju-gahlawat
http://www.bradvg.com/blog/the-problem-with-good-intentions/
KurtKamka https://www.getdpi.com/forum/leica/21559-s-show-us-your-s2-shots-22.html
https://tisquirrel.me/2016/01/03/say-agile-one-more-time/
http://www.br.de/themen/wissen/inhalt/umwelt/wueste-wuestentiere104.html
https://blogs.msdn.microsoft.com/eugeniop/2010/05/24/windows-azure-architecture-guide-part-1-release-candidate-documents-updated/
http://eduart4kids.com/painting-for-kids/
https://image.slidesharecdn.com/quangnguyencontinuousintegrationxpday2015danangquangnguyen-150520014341-lva1-app6892/95/quang-nguyen-continuous-integration-xp-day-2015-vietnam-danang-3-638.jpg?cb=1432086426
https://blogs.msdn.microsoft.com/willy-peter_schaub/2010/11/22/are-the-rangers-courageous-or-crazy-to-brainstorm-and-adapt-methodologies-from-clever-people-as-part-of-ruck/
https://dotnetcodr.files.wordpress.com/2015/07/ddd-full-diagram1.png
https://images-na.ssl-images-amazon.com/images/I/81vKl1%2BuEVL._SL1500_.jpg
https://dotnetcodr.files.wordpress.com/2015/07/ddd-full-diagram1.pnghttp://canarydwarf.co.uk/b/wp-content/uploads/2014/05/CD_questions_68942389.jpg
https://www.batimes.com/images/wick_mar4_2.jpg
https://guidedpathedge.com/wp-content/uploads/2016/01/keep-calm-and-prioritize.png