Project Boomerang aims to fundamentally transform the bol.com returns process. I’ll share the underlying architectural structure, explain how the code matches the structure and how we’ve applied test autonomy concepts within this architecture. Spoiler alert: it turns out they fit together surprisingly well. Ultimately, I want to convince you of the value of having a clear idea on how to structure your service. This presentation was given during the the Spaces Summit, an internal IT conference by and for the engineers of bol.com.

1. Building a Boomerang that doesn't come back
(to haunt you)
BOL.COM SPACES SUMMIT 2017
By Mattijs Meiboom ( )mmeiboom@bol.com

2. 3 years at bol.com
So ware Engineer (Fulfilment Space)
Team 21b (C4)
Today: Boomerang!
About me

6. Provides a structure to the code base
Helps us develop & test in isolation
Protects us against the scary world
outside
WE WANT SOMETHING THAT…

7. HEXAGONAL ARCHITECTURE
TEST AUTONOMY
“Allow an application to equally be
driven by users, programs, automated
tests or batch scripts, and to be
developed and tested in isolation from
its eventual run-time devices and
databases.”— Alistair Cockburn
“Improve testability by building tests
that are reliable, give fast feedback,
are independent and isolated.”

15. Execute a task on a single node at some interval
Scheduling
Leadership election
Internal locking
AN EXAMPLE: JOB SCHEDULING

16. AN EXAMPLE: JOB SCHEDULING
public interface Job {
void run();
}

17. AN EXAMPLE: JOB SCHEDULING
public interface Scheduler {
void register(Job job);
}

18. AN EXAMPLE: JOB SCHEDULING
public class ReceivedReturnsJob implements Job {
private final ReceivedReturnsCollector collector;
public ReceivedReturnsJob (
ReceivedReturnsCollector collector,
Scheduler scheduler
) {
this.collector = collector;
scheduler.register(this);
}
@Override
public void run() {
collector.collect();
}

19. AN EXAMPLE: JOB SCHEDULING
public class SingleNodeScheduler extends ... implements Scheduler {
@Override
public void register(Job job) {
jobs.add(job);
}
@Override
protected void onAcquiredLeadership() {
jobs.forEach(this::scheduleJob);
}
private void scheduleJob(Job job) {
Subscription subscription = Observable.interval(...)
.subscribe(timeout -> { // hiding locking and other details
job.run();
});
}
}

20. HEXAGONAL ARCHITECTURE
TEST AUTONOMY
“Allow an application to equally be
driven by users, programs, automated
tests or batch scripts, and to be
developed and tested in isolation from
its eventual run-time devices and
databases.”— Alistair Cockburn
“Improve testability by building tests
that are reliable, give fast feedback,
are independent and isolated.”

27. Structure
Separation of responsibilites…
…also for testing
It hasn’t been perfect, but the common ground proves
very valuable.
WHAT HAS IT BROUGHT US SO FAR?

28. RESOURCES
Freeman & Pryce — Growing object oriented so ware
Pryce — Visualising Test Terminology
Techlab — How structure helps me to maintain so ware
Confluence — Test Autonomy

29. Questions?
BOL.COM SPACES SUMMIT 2017
Mattijs Meiboom ( )mmeiboom@bol.com