Designing, building, testing and deploying microservices. A stairway to heaven or a highway to hell? - Sander Hoogendoorn - Codemotion Amsterdam 2016

@aahoogendoorn | www.ditisagile.nlMicroservices. Stairway to heaven or highway to hell? 1
@aahoogendoorn | www.ditisagile.nl
Microservices.
Stairway to heaven
or highway to hell?
Sander Hoogendoorn
ditisagile.nl
Mentoring ▪ Consulting ▪ Training
Agile ▪ Software
architecture ▪ Code

Sander Hoogendoorn
Me
Dad
Mentor, trainer, software architect,
programmer
Books, articles, conferences
Work
Owner ditisagile.nl
CTO Klaverblad Verzekeringen
Web
www.sanderhoogendoorn.com
@aahoogendoorn
sander@ditisagile.nl

As a project manager
I would like to demo untested code so I embarrass myself

Monoliths
Hard to deliver,
even harder to test
and impossible to maintain

Who doesn’t have a system that is too big
and that really should be broken up?

Advantages
A single (layered) architecture
A single technology stack
A single code base maintained by multiple teams
Disadvantages
All parts are interconnected
Many other systems are connected to your system
Hard to change, hard to maintain
Long time between releases, thereby increasing risks
Slow innovation
Hard to move to newer technologies
Doesn’t scale very well
Monoliths
Advantages and disadvantages

Dependencies will kill you
A typical systems landscape

A brief history
of components
and services

My first computer

Client server

Component based development

Service oriented architecture

Microservices

Microservices
Beyond the hype?

Gartner hype cycle

Microservices
The clear benefits

But first … a definition

In short, the microservice architectural style is an approach
to developing a single application as a suite of small services,
each running in its own process and communicating with
lightweight mechanisms, often an HTTP resource API.
These services are built around business capabilities and
independently deployable by fully automated deployment
machinery. There is a bare minimum of centralized
management of these services, which may be written in
different programming languages and use different data
storage technologies.
Martin Fowler

Monoliths
Scalability

Microservices
Scalability

Microservices
Running in their own processes

Monoliths
Persistence

Microservices
Polyglot persistence

Products not projects
Scalable
Decentralized governance
Replaceable parts
High performance
Technology independent
Polyglot persistence
Easy to build
Easy to test
Easier deployment than monoliths
Microservices
Promises

What is a microservice exactly?
How small is a microservice?
Requirements in a microservice world
Components or services
Who owns a microservice?
What technologies do you use?
What protocols do you apply?
How to define messages
How to test microservices
How to coordinate when business services run
across components?
How to build deployment pipelines?
Microservices
But…

Opinions, opinions, opinions

Are microservices
a stairway to
heaven?

Or are they
a highway to hell?

Where do we come from?
Case 1

Case 1

Where are we going to?
Case 1

For the things we have to learn
before we can do them,
we learn by doing themAristotle

Welcome under
the umbrella

So what did
we learn?

Microservices require
an evolutionary software architecture

Start with some
guiding principles

Client thinks in business processes, so we implement business
processes
We move away from the mainframe, to a new systems
landscape, consisting of micro-applications and micro-
components
Requirements and documentation are modeled rather than
written
Applications implement a single (elementary) business
process
Components serve a single purpose and offer services
Applications and components all have their own bounded
context – a domain model
Applications and components will have an similar internal
software architecture to facilitate ease of maintenance and
allow for harvesting re-use
Communication between applications and components will
use a simple open protocol - REST
Some guiding principles
Case 1

Designing
microservices
Modular design and
bounded contexts

Doing big up-front design is dumb,
doing no design is even dumber
Dave Thomas

Bounded contexts

Domain driven design
The paradigm of designing software based on models
of the underlying domain
The domain model helps the business and the
developers to reason about the functionality
A model needs to be unified – internally consistent
without contradictions
Bounded context
The bounded context is a central pattern in domain
driven design
When you model larger domains, it becomes
progressively harder to create this single unified model
So, instead of creating a single unified model, you create
several, all valid within their bounded context
Bounded context

The single unified domain model
Or more often the humongous data model

Bounded contexts

Modeling
resources

RESTfulness
is not as easy
as it seems

HTTP return codes cheat sheet
1**. Hold on
2**. Here you go
3**. Go away
4**. You fucked up
5**. I fucked up

Be conservative in what you send,
be liberal in what you accept
Postel’s Law

Postel’s Law
Be conservative in what you send, be liberal in what you accept

Testing
microservices

Fail fast, fail often, fail forward

Even though you might have really brilliant testers…

A service development lifecycle

… please automate all your tests

Towards minimal
viable products
Kaizen and continuous
delivery

Small increments or big releases?
What if Twitter…

Minimal viable product

From projects to continuous delivery

An approach in which teams ensure that every
change to the system is releasable, and that we
can release any version at the push of a button.
Aimed to make releases boring, so we can deliver
frequently and get fast feedback on what users
care about.
Jez Humble

You build it, you run it
Werner Vogels

DevOps is not easy
It feels like showing up at the wrong re-enactment

In retrospective
Some final thoughts

Microservices are not for everyone (yet)
Under the umbrella

The hockey stick model

Minimal viable product

Allow your teams
to learn
continuously

And don’t forget
to have fun

References
and questions
www.sanderhoogendoorn.com
www.smartusecase.com
www.speedbird9.com
sander@ditisagile.nl
@aahoogendoorn

Designing, building, testing and deploying microservices. A stairway to heaven or a highway to hell? - Sander Hoogendoorn - Codemotion Amsterdam 2016

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Designing, building, testing and deploying microservices. A stairway to heaven or a highway to hell? - Sander Hoogendoorn - Codemotion Amsterdam 2016