epilogue_1_how_to_get_there_from_here.asciidoc

Epilogue: How Do I Get There From Here?

Note	TODO, chapter under construction

OK, but how do I get there from here?

• Option 1: carve out microservices one by one

• Option 2: refactoring inside your monolith

In either case, you’ll need to figure out what the correct Bounded Context is.

• fork the repo and delete stuff that’s not in your bounded context

• strangler pattern. can start with just an HTTP proxy

• what are peloton doing?

What do you want to achieve?

What’s the problem with a monolith? there’s no domain model because everything is trying to be all things to all people

-→ you need to carve out bounded contexts and probably microservices

Is it that all the logic is hard to find because it’s mixed between all the layers?

A django story

• introducing a Service Layer first

  • define use cases

  • messagebus can come later

  • push all the logic down into the models

• once we have rich django models

  • migrate them one by one to POPO classes

  • add repository to translate

  • ⇒ now we can refactor the model (semi/more) independently from the DB

• and we can keep going and add UoW and a messagebus

  • now we have the event-driven / command handler pattern

  • almost any business requirement can be decomposed sensibly

see [appendix_django]

an event-driven approach to go microservices via strangler pattern

• get your system to produce events

• consume them in your new service. we now have a separate db and bounded context

• the new system produces

  • either the same events the old one did (and we can switch those old parts off)

  • or new ones, and we switch over the downstream things progressively

Footguns

This is a part 2 thing really, but basically, don’t sally forth and implement your own event-driven microservices architecture without reading lots, lots more on the subject.

https://martinfowler.com/books/eip.hgirl rubytml[Enterprise Integration Patterns] by (as always) Martin Fowler is a pretty good start.