Presentation at JOIN 2019 (https://join.di.uminho.pt/)

1. Shifting to microservices in the
real world
Luís Barbosa | 4th June 2019

2. The Microservice Ecosystem

3. 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.
-- James Lewis & Martin Fowler
Microservice oriented architecture

4. Strong Module Boundaries
Independent Deployment
Technology Diversity
Microservices provide benefits…
Independent Scalability

5. Distribution
Eventual Consistency
Operational Complexity
…but come with costs
Testing Complexity

6. Use Case: e-Commerce Application

7. The Monolith
Discount
Pricing
Checkout
Identity
…

8. The real world challenges
100% growth/year
More projects than teams capacity to deliver
All projects are priority
Value perceived by the business

9. Embrace the journey

10. What to extract first?
Simple fairly decoupled capability
Edge services
Practice the operational prerequisites
Decoupling capabilities deeply embedded as next step

11. Avoid dependencies to the monolith
Couples the service to the monolith's release cycle
Reverse dependency direction
Minimize dependency to the Monolith

12. Leaky, not well defined domain concept
Identify leaky capabilities
Deconstruct into a well defined domain concept
Split sticky capabilities
Refactor and extract into new services

13. Decouple the data along with service
Data migration strategy
Anti-pattern: decoupling façades
Decouple vertically

14. Extract code or rewrite
Reuse and Extract high value code with low toxicity
Rewrite and Retire low value code with high toxicity
Decouple capability and not code

15. Start with larger services around a rich domain concept
Breakdown services to smaller domain concepts
DDD Bounded Contexts
Go macro first
Anti-pattern: Anemic Services

16. Decouple the new service
Redirect all consumers to new service
Retire the old code path in the monolith
Do it in atomic steps
Anti-pattern: Split new and old consumers

17. Q&A
Thank you!