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

How can we better collaborate on creating useful APIs? How to reduce the testing time of your application? How can the team build API backwards compatibility verification into their deployment process?

In this talk, I will discuss how to leverage the Consumer-Driven Contracts approach to solve these and other issues and present one of CDC implementations - Spring Cloud Contract. We will discuss practical use-cases and look at code examples. I will also point out some of the possible issues and ways of handling them, as well as some good practices I have learnt while working both as a CDC tools end-user and their developer.

Transcript

1. Olga Maciaszek-Sharma
   June 2020
   Better APIs, faster tests and more
   resilient systems with Spring Cloud
   Contract
   Copyright © 2020 VMware, Inc. or its affiliates.
   

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2. 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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3. What will we try to improve?
   

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4. Faster Tests
   

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5. The Monolith
   Service 1 Service 2 Service 3
   

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6. A LOT of E2E tests
   

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

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

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9. Hell automation
   @venkat_s
   

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10. E2E tests
    Slow
    Unstable
    Rely on collaborators
    Reliable
    

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11. 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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12. Fast development, fast tests
    

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13. Decoupling deployment
    

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14. Agile teams, agile releases
    

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15. Fail Safe Safe To Fail
    

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16. Shift to the Left
    

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17. Network Communication
    Stubs
    

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

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

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20. A new endpoint
    

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21. A new endpoint
    

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

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23. 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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24. Stubs alone don’t guarantee
    ANYTHING
    

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25. Stubbed tests
    Unreliable
    Fast
    Stable
    Independent
    

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26. Better APIs
    

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27. The Monolith
    Service 1 Service 2 Service 3
    

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28. A server with limited clients
    

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29. Limited APIs
    

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30. External APIs
    

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31. Limited Network
    Communication for Internal
    Apps
    

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32. 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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33. Network communication as
    first-class citizen
    

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

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35. Numerous fast-growing and
    (even) changing internal APIs
    

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36. Possibility of
    COLLABORATION between
    API producers and
    consumers
    

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37. Some terms
    Producer Consumer
    

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38. Why would we want to do
    that?
    

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39. It’s the consumer that
    actually CONSUMES the API.
    

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

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42. Potential Answer:
    Consumer-Driven Contracts
    

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43. Contracts
    Contract
    Consumer
    Input A
    Producer
    Output B
    

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

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45. Possible Implementation:
    Spring Cloud Contract
    

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46. 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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47. 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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48. 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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49. 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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50. 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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51. 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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52. 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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53. 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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54. 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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55. 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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56. 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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57. 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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58. 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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59. Consumer Build Setup
    
    org.springframework.cloud
    spring-cloud-starter-contract-stub-runner
    test
    
    

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60. 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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61. 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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62. 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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63. Code Demo
    

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64. 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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65. 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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66. 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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67. Code Demo
    

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68. 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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69. Architecture and Deployments
    

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70. Architecture/ API TDD
    Refactor
    Red
    Green
    

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

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72. 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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73. Lessons Learnt and Good
    Practices
    

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74. Usage
    Logic tests in lower layers
    

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75. Resilience
    Monitoring
    Logging
    Alerting
    

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76. Maintenance
    Skipping contracts for non-essential
    functionalities
    

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77. Maintenance
    Skipping multiple values
    

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78. 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
    

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79. Thank you
    Contact me at omaciaszeksh@vmware.com
    © 2020 Spring. A VMware-backed project.
    

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