Consumer Driven Contracts for Microservices

By Reshmi Krishna By Vinay Upadhya @reshmi9k @vinayu

About Us Reshmi Krishna

● Software Engineer● Platform Architect, Pivotal Cloud

Foundry● Women In Tech Community Member

Twitter : @reshmi9k MeetUp : Cloud-Native-New-York

Vinay Upadhya

● Software Engineer● Platform Architect, Pivotal Cloud

Foundry● Application Architecture Evangelist

Twitter : @vinayu

Agenda

What are Consumer Driven Contracts?

What problems are we trying to solve?

Spring Cloud Contract for microservices

Demo

What are Consumer Driven Contracts?

Internal Marketing

App

External Reseller

App

Product SearchService

API

{ catalogid, name, price, manufacturer }

{ catalogid, name, price }

Product Schema

{ catalogid, name, price, manufacturer,inStock }

Producer Contract

Expectation

Consumer Contract

Consumer Driven Contract

What are Consumer Driven Contracts ( CDC )

Not a new concept but becoming more prevalent in today’s world of microservices.

It is a pattern for evolving services and their API’s without breaking backward or forward compatibility.

CDC driven testing is TDD applied at an architectural level of the project.

What problems are we trying to solve?1.Provide a framework for consumers

to set expectations with consumer contracts and drive the producer API.

2.Producer test lifecycle includes validating consumer contracts.

3.Provide reusable producer stubs for consumers to use in their integration tests.

4.Minimize E2E integration tests.

Spring Cloud ContractSpring Cloud Contract provides support for CDC and service schemas in Spring

Apps.

Being part of Spring Cloud it can help stub out Spring Cloud components like Eureka, Consul etc.

Comprised of three main projects :-

Spring Cloud Contract Verifier : Library on server side to test if the server isn’t breaking any consumer contracts.

Spring Cloud Contract Wiremock : Wrapper around wiremock to help start stubs with wiremock json stubs.

Spring Cloud Contract Stub Runner : Helper library to pull stubs from maven and run them with wiremock.

What is a contract?

Demo

I want to login Can Reshmi/123 login ?

YES !!!! OK

Demo

I want to login Can Vinay/321 login ?

No !!!! NOT_OKAY

Typical CDC Flow Consumer Phase 1 Producer Phase Consumer Phase 2

Consumer Offline Work

Producer Implementing Feature

Consumer Online Work

Consumer Flow 1 (Login Client)Start TDD - writes the test for the feature

Write the missing implementation

Clone the Producer (LoginServerService) repository locally

Define the contract locally in the repo of Producer

Add the Spring Cloud Contract Verifier plugin

Run the integration tests

Producer Flow (Login Server)

Take over the PR

Write the missing implementation that will make the autogenerated

tests pass

Merge PR and deploys the JARs with the app and the stubs

Consumer Flow 2 (Login Client)

Switches off the Stub Runner’s offline mode once the producer

uploads the stubs

Configure Stub Runner by providing the URL to a repo with stubs

Will have its test broken if the producer makes any breaking changes

of the API

Demo : Add additional parameter to login

Login Validate(UN,PWD,AC)

Response Response

ResourcesDocs : https://cloud.spring.io/spring-cloud-contract/spring-cloud-contract.html

MeetUp Demo : https://github.com/reshmik/spring-cloud-contract-login-demo.git

Consumer Driven Contracts (MarcinGrzejszczak) : http://www.slideshare.net/MarcinGrzejszczak/consumer-driven-contracts-and-your-microservice-architecture-67641511

More Samples : https://github.com/spring-cloud/spring-cloud-contract/tree/1.0.x/samples

Talk to the SpringCloudContract Team : https://gitter.im/spring-cloud/spring-cloud-contract