Consumer Driven Contracts with Spring Cloud Contract 

Disclaimer Presentations are intended for educational purposes only and not to replace independent professional judgment. The views and opinions expressed in this presentation do not necessarily reflect the official policy or position of blibli.com. Audience discretion is advised. 

Who Am I? • Alex Xandra Albert Sim • Principal R&D Engineer at blibli.com • [email protected] • bertzzie(.sim) 

The Hype MICROSERVICES! 

Our Current System • Hundreds of microservices • All on the JVM, except UIs and Mobile • Most are on Spring Framework 

How do services talk to each other? Service Client A Client B Client C Interface 

Provider Contract • The service defines the interface, everyone use it • Close and complete • Singular and authoritative • (Usually) stable and immutable 

The Microservice Problem • Managing Changes • How are people using my service(s)? • Stubs / Mocks. TONS of it. • Release Engineering requires 5 PHDs, 3 geniuses, and 1 Norse God • Short Release Cycle and Continuous Delivery only available in Wakanda • QA L 

Enter Consumer Driven Contract Service Client A Client B Client C Data A Data B 

Consumer Contract • Consumers define their interfaces to the service • There’s still conventions and limits (duh) • Open and incomplete • Multiple and non-authoritative • (Usually) stable and immutable 

Consumer Driven Contract - How does it work? Source: http://servicedesignpatterns.com/WebServiceEvolution/ConsumerDrivenContracts 1 2 3 4 

Consumer Driven Contract - How does it work? 1. Each consumer write their executable tests 2. Producer reviews and approves the tests written 3. Producer test against the tests and make sure it all passes PS. The test could be on separate repo or on producer’s 

Why Consumer Driven? • Service providers now know how their service is used • Evolving the service is easier • Could be easily integrated to CI / CD systems • Better confidence in each release • No more manual stub / less mocks 

Further Reading • https://martinfowler.com/articles/consumerD rivenContracts.html • http://cloud-samples.spring.io/spring-cloud- contract-samples/workshops.html 

Thank You