Better APIs, faster tests and more resilient systems with Spring Cloud Contract

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About me Software Engineer in Spring Cloud Team ● Spring Cloud LoadBalancer (Spring Cloud Commons) ● Spring Cloud Contract ● Spring Cloud OpenFeign ● Spring Cloud Netﬂix https://github.com/OlgaMaciaszek https://twitter.com/olga_maciaszek

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What will we try to improve?

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Faster Tests

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The Monolith Service 1 Service 2 Service 3

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A LOT of E2E tests

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Failing pipelines source: https://www.jenkins.io/blog/2016/05/26/introducing-blue-ocean/

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Long build and test times source: https://ci.jenkins.io/

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Hell automation @venkat_s

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E2E tests Slow Unstable Rely on collaborators Reliable

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Distributed architectures IoT API Gateway Mobile Browser Service 1 Service 3 Conﬁg Server Service Registry Spring Cloud Sleuth Service 2 Metrics Store Databases Message Brokers PLATFORM

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Fast development, fast tests

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Decoupling deployment

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Agile teams, agile releases

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Fail Safe Safe To Fail

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Shift to the Left

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Network Communication Stubs

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A new endpoint { “request” : { “method”: “GET”, “url” : “/endpointX”, }, “response” : { “status” : 200 } }

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A new endpoint { “request” : { “method”: “GET”, “url” : “/endpointX”, }, “response” : { “status” : 200 } }

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A new endpoint

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A new endpoint

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A new endpoint { “request” : { “method”: “GET”, “url” : “/endpointX”, }, “response” : { “status” : 200 } } { “request” : { “method”: “GET”, “url” : “/endpointY”, }, “response” : { “status” : 200 } }

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Messaging topic: yyy class Product { int productId; String productName; } topic: xxx class Product { int id; String productName; } topic: xxx class Product { int productId; String productName; }

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Stubs alone don’t guarantee ANYTHING

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Stubbed tests Unreliable Fast Stable Independent

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Better APIs

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The Monolith Service 1 Service 2 Service 3

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A server with limited clients

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Limited APIs

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External APIs

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Limited Network Communication for Internal Apps

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Distributed architectures IoT API Gateway Mobile Browser Service 1 Service 3 Conﬁg Server Service Registry Spring Cloud Sleuth Service 2 Metrics Store Databases Message Brokers PLATFORM

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Network communication as ﬁrst-class citizen

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Multiple instances of many services communicating with each other over the network

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Numerous fast-growing and (even) changing internal APIs

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Possibility of COLLABORATION between API producers and consumers

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Some terms Producer Consumer

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Why would we want to do that?

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It’s the consumer that actually CONSUMES the API.

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It makes sense for the consumer to actually DRIVE the creation of the APIs

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No content

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Potential Answer: Consumer-Driven Contracts

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Contracts Contract Consumer Input A Producer Output B

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Consumer-Driven Contracts https://martinfowler.com/articles/consumerDrive nContracts.html https://martinfowler.com/bliki/ContractTest.html

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Possible Implementation: Spring Cloud Contract

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Spring Cloud Contract - Consumer-Driven Contract Flow Consumer ● Checks out Producer code repo and works locally on a contract ● Creates a pull request with the new Contract ● Collaborates with the Producer on the Contract PR ● Uses stubs published by the producer along the app for integration tests Producer ● Reviews the Contract PR ● Runs build on the PR branch (FAILURE) ● Adds required endpoints ● Runs build on the PR branch (PASSING) ● Code Deployed along with generated stubs jar

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Producer Build Setup org.springframework.cloud spring-cloud-contract-maven-plugin 2.2.3.RELEASE true JUNIT5 WEBTESTCLIENT FraudCheckTestsBaseClass org.springframework.boot spring-boot-maven-plugin

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Contract Contract.make { request { method 'POST' url '/fraudcheck' body( clientId: anyUuid(), loanAmount: 99999 ) headers { header('Content-Type', 'application/vnd.fraud.v1+json;charset=UTF-8')} } response { status 200 body( fraudCheckStatus: "FRAUD", rejectionReason: "Amount too high") headers { header('Content-Type': 'application/vnd.fraud.v1+json;charset=UTF-8')} } }

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Contract request: method: POST url: /fraudcheck body: clientId: 437ea752-7361-4d55-ad3d-2dcc40204acf loanAmount: 99999 headers: Content-Type: application/vnd.fraud.v1+json;charset=UTF-8 matchers: body: - path: $.['clientId'] type: by_regex predefined: uuid response: status: 200 body: fraudCheckStatus: "FRAUD" rejectionReason: "Amount too high" headers: Content-Type: application/vnd.fraud.v1+json;charset=UTF-8

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Generated Contract Test @Test public void validate_shouldMarkClientAsFraud() throws Exception { // given: WebTestClientRequestSpecification request = given() .header("Content-Type", application/vnd.fraud.v1+json;charset=UTF-8") .body("{\"clientId\":\"437ea752-7361-4d55-ad3d-2dcc40204acf\",\"loanAmount\":99999}"); // when: WebTestClientResponse response = given().spec(request) .post("/fraudcheck"); // then: assertThat(response.statusCode()).isEqualTo(200); assertThat(response.header("Content-Type")) .isEqualTo("application/vnd.fraud.v1+json;charset=UTF-8"); // and: DocumentContext parsedJson = JsonPath.parse(response.getBody().asString()); assertThatJson(parsedJson).field("['fraudCheckStatus']").isEqualTo("FRAUD"); assertThatJson(parsedJson).field("['rejectionReason']").isEqualTo("Amount too high"); }

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Generated WireMock Stub { "id" : "88dd475b-005d-4a1d-a6c5-3d40493c8d37", "request" : { "url" : "/fraudcheck", "method" : "POST", "headers" : { "Content-Type" : { "equalTo" : "application/vnd.fraud.v1+json;charset=UTF-8" }}, "bodyPatterns" : [ { "matchesJsonPath" : "$[?(@.['loanAmount'] == 99999)]" }, { "matchesJsonPath" : "$[?(@.['clientId'] =~ /([a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12})/)]" } ] }, "response" : { "status" : 200, "body" : "{\"fraudCheckStatus\":\"FRAUD\",\"rejectionReason\":\"Amount too high\"}", "headers" : { "Content-Type" : "application/vnd.fraud.v1+json;charset=UTF-8" }, "transformers" : [ "response-template" ]}, "uuid" : "88dd475b-005d-4a1d-a6c5-3d40493c8d37"}

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Consumer Build Setup org.springframework.cloud spring-cloud-starter-contract-stub-runner test

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Consumer Tests @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE) @ExtendWith({SpringExtension.class}) @AutoConfigureStubRunner(ids = {"io.github.olgamaciaszek:scc-producer-demo:+:stubs:8080"}, stubsMode = StubRunnerProperties.StubsMode.REMOTE) class SccConsumerDemoApplicationTests { @Test void shouldBeRejectedDueToAbnormalLoanAmount() { LoanApplication application = new LoanApplication(new Client(UUID.randomUUID()), new BigDecimal("99999"), UUID.randomUUID()); LoanApplicationResult loanApplication = loanApplicationService .loanApplication(application).block(); assertThat(loanApplication.getLoanApplicationStatus()) .isEqualTo(LoanApplicationStatus.APPLICATION_REJECTED); assertThat(loanApplication.getRejectionReason()).isEqualTo("Amount too high"); }}

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Consumer Tests @StubRunnerPort port; stubrunner: ids: - org.springframework.cloud.contract.verifier.stubs:loanIssuance - org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer - org.springframework.cloud.contract.verifier.stubs:bootService

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Consumer Tests @Rule public StubRunnerRule rule = new StubRunnerRule() .downloadStub("com.example","fraud-service") .stubsMode(StubRunnerProperties.StubsMode.LOCAL) .withStubPerConsumer(true) .withConsumerName("loan-service"); int fraudServicePort = rule.findStubUrl("fraud-service").getPort()

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Code Demo

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Messaging Contract Contract.make { label "payment_successful" input { triggeredBy "makeSuccessfulPayment()" } outputMessage { sentTo "payments" body( uuid: "d64c361b-29bb-43a9-8fe8-5e7e05493842", status: "SUCCESS" ) headers { header("contentType", applicationJson())}}}

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Generated Contract Test @Test public void validate_should_payment_fail() throws Exception { // when: makeFailingPayment(); // then: ContractVerifierMessage response = contractVerifierMessaging.receive("payments"); assertThat(response).isNotNull(); // and: assertThat(response.getHeader("contentType")).isNotNull(); assertThat(response.getHeader("contentType").toString()).isEqualTo("application/json"); // and: DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.getPayload())); assertThatJson(parsedJson).field("['uuid']").isEqualTo("d64c361b-29bb-43a9-8fe8-5e7e05493842"); assertThatJson(parsedJson).field("['status']").isEqualTo("FAILURE"); }

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Consumer Test @SpringBootTest @AutoConfigureStubRunner(stubsMode = StubRunnerProperties.StubsMode.LOCAL, ids = "com.example:scc-payment") class PaymentProcessingSpec extends Specification { @Autowired StubTrigger stubTrigger def 'should handle successful payment'() { when: stubTrigger.trigger('payment_successful') then: accountingService.successfulPayments.size() == 1 }

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Code Demo

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Spring Cloud Contract A few highlighted features out of many: ● Contracts in a separate repository ● Spring Cloud Netﬂix and Spring Cloud LoadBalancer integration ● Creating Spring Rest Docs from Contracts and Contracts from Spring Rest Docs ● Polyglot support (using provided Docker image) ● Community support for Swagger ﬁles

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Architecture and Deployments

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Architecture/ API TDD Refactor Red Green

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Backward Compatibility Checks in Pipelines New API version Test with PROD contracts Deploy Test with new contracts

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Deferred updates Deployment Contract ﬁelds Application ﬁelds 0 { "buildTime": 5 } { "buildTime": 5 } 1 { "buildTime": 5, "buildTimeMillis": 5000 } { "buildTime": 5, "buildTimeMillis": 5000 } 2 { "buildTimeMillis": 5000 } { "buildTime": 5, "buildTimeMillis": 5000 } 3 { "buildTimeMillis": 5000 } { "buildTimeMillis": 5000 }

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Lessons Learnt and Good Practices

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Usage Logic tests in lower layers

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Resilience Monitoring Logging Alerting

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Maintenance Skipping contracts for non-essential functionalities

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Maintenance Skipping multiple values

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Resources ● Project page ● Samples ● https://github.com/OlgaMaciaszek/scc-producer-demo ● https://github.com/OlgaMaciaszek/scc-consumer-demo ● https://github.com/OlgaMaciaszek/scc-payment ● https://github.com/OlgaMaciaszek/scc-shop ● Spring Cloud Contract at Devskiller - case study ● https://gitter.im/spring-cloud/spring-cloud-contract