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Architecture Patterns with Python
Enabling Test-Driven Development, Domain-Driven Design, and
Event-Driven Microservices
Harry Percival and Bob Gregory
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Architecture Patterns with Python
by
Harry Percival and Bob Gregory
Copyright © 2020 Harry Percival and Bob Gregory. All rights reserved.
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Preface
You may be wondering who we are and why we wrote this book.
At the end of Harry’s last book, Test-Driven Development with Python (O’Reilly), he
found himself asking a bunch of questions about architecture, such as, What’s the best
way of structuring your application so that it’s easy to test? More specifically, so that
your core business logic is covered by unit tests, and so that you minimize the number
of integration and end-to-end tests you need? He made vague references to
“Hexagonal Architecture” and “Ports and Adapters” and “Functional Core,
Imperative Shell,” but if he was honest, he’d have to admit that these weren’t things
he really understood or had done in practice.
And then he was lucky enough to run into Bob, who has the answers to all these
questions.
Bob ended up a software architect because nobody else on his team was doing it. He
turned out to be pretty bad at it, but he was lucky enough to run into Ian Cooper, who
taught him new ways of writing and thinking about code.
Managing Complexity, Solving Business Problems
We both work for MADE.com, a European ecommerce company that sells furniture
online; there, we apply the techniques in this book to build distributed systems that
model real-world business problems. Our example domain is the first system Bob
built
for MADE, and this book is an attempt to write down all the stuff we have to
teach new programmers when they join one of our teams.
MADE.com operates a global supply chain of freight partners and manufacturers. To
keep costs low, we try to optimize the delivery of stock to our warehouses so that we
don’t have unsold goods lying around the place.
Ideally, the sofa that you want to buy will arrive in port on the very day that you
decide to buy it, and we’ll ship it straight to your house without ever storing it.
Getting the timing right is a tricky balancing act when goods take three months to
arrive by container ship. Along the way, things get broken or water damaged, storms
cause unexpected delays, logistics partners mishandle goods, paperwork goes
missing, customers change their minds and amend their orders, and so on.
We solve those problems by building intelligent software representing the kinds of
operations taking place in the real world so that we can automate as much of the
business
as possible.
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