Future of Jira Software powered by Kotlin - Kotlin Night Ankara

Atlassian is on a decomposition journey. We split our monoliths in microservices and we build our microservices in Kotlin. Our services are reactive and resilient and working on them is kool.

This is a story of Jira Software’s transition to Kotlin. How we built a GraphQL gateway in Kotlin with Spring Boot and Project Reactor. Our success in interoperability with Java and how we solved issues when crossing the boundary between the reactive and non-reactive world. It also explains how Kotlin helped our developers become more productive and how resilience helps us build better services for consumers.

Transcript

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2. MARTIN VARGA | SOFTWARE DEVELOPER | @MARTINTEEVARGA
   Future of Jira Software
   Powered by Kotlin
   

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4. kotlinlang.org
   

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6. Google
   Pixel 2
   Just Black
   Simply drop
   your screenshot
   on to this
   media
   placeholder
   TRELLO MOBILE
   

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7. Jira
   For cloud and server
   Confluence
   For cloud and server
   OpsGenie
   Our recent acquisition
   Not just Trello
   

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8. Not just mobile!
   

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9. FUTURE OF JIRA SOFTWARE
   POWERED BY KOTLIN
   

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10. JIRA SOFTWARE?
    

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11. Plan, track and
    release software.
    JIRA SOFTWARE
    

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13. The Story of Jira
    From the developer’s perspective
    

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14. Server Cloud
    1001001
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    Single Code Base
    

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15. Server Cloud
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16. 1101010
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18. 1101010
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25. 1101010101010100
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26. 1101010101
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27. 1101010
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28. 1101010
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29. 1101010
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31. How Atlassian builds services
    Making developers productive with platform as a service
    

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32. PaaS that allows
    devs to create and
    deploy a service in
    matter of minutes.
    MICROS
    

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33. MICROS
    

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34. name: "animalfacts"
    compose:
    animalfacts:
    image: internal.docker.repo/animalfacts
    tag: 'PROJECT_VERSION'
    ports:
    - 8080:8080
    MICROS DESCRIPTOR
    

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35. links:
    healthcheck:
    uri: heartbeat
    port: 8080
    source:
    url: "git@bitbucket.org:atlassianlabs/animal-facts-
    graphql-gateway-demo.git"
    notifications:
    email: "animalfactsowner@atlassian.com"
    resources:
    - type: dynamo-db
    name: facts
    attributes:
    ReadWriteCapacityMode: ON_DEMAND
    

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36. Jira Software Tech Stack
    DynamoDB or PostgreSQL
    Depends on the application.
    Project Reactor
    Mature reactive library.
    Kotlin
    For all new services.
    Spring Boot
    Custom wrapper that makes
    monitoring etc. easier.
    

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37. Powered by Kotlin
    Making developers happy
    

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38. WHY KOTLIN?
    

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39. Experience
    Have we learned Kotlin enough? Was it a
    success?
    Compatibility
    How well is it going to play with our current tech
    stacks?
    Staffing
    Are we going to have enough Kotlin developers
    available?
    Adopting
    Kotlin
    

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40. Velocity
    Does it make our developers more productive?
    Industry
    Is it already adopted by the developers
    community?
    Adopting
    Kotlin
    

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41. ❤
    

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42. Experienced with Kotlin.
    Android Developer Ad
    

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43. Experience or interest in Kotlin
    development.
    Software Engineer, Developer Productivity, Jira Cloud Ad
    

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44. We happen to have a variety of
    languages within our stack
    including Kotlin, Python, and
    Ruby.
    Senior Backend Developer Ad
    

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45. A case for a reactive app
    A real world example of an app that we built recently
    

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46. LATENCY
    250ms
    250ms
    250ms
    750ms
    

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47. LATENCY
    10ms
    250ms
    10ms
    10ms
    280ms
    

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48. Operators
    Useful for modifying and combining sources.
    Allows composition of libraries that add
    resilience, tracing etc.
    Async
    Calls a service, then does mostly nothing and
    waits. Perfect fit.
    Project
    reactor
    Clean code
    No callback hell.
    

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49. val currentBoard = “5”.toMono()
    MONO
    5
    

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50. val recentBoards = listOf("0", "1", "2").toFlux()
    FLUX
    0 1 2
    

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51. val currentBoard = "5".toMono()
    val recentBoards = listOf("0", "1", "2").toFlux()
    currentBoard.concatWith(recentBoards)
    COMPOSITION & CLEAN CODE
    5
    0 1 2
    0 1 2
    5
    

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52. val currentBoard = "5".toMono()
    val recentBoards = listOf("0", "1", "2").toFlux()
    currentBoard.concatWith(recentBoards)
    .map {
    boardService.getName(it)
    }
    .take(3)
    .subscribe {
    println(it)
    }
    COMPOSITION & CLEAN CODE
    

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53. Surfboard
    Skateboard
    Ironing board
    COMPOSITION & CLEAN CODE
    

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54. currentBoard.concatWith(recentBoards)
    .map {
    boardService.getName(it)
    }
    .timeout(Duration.ofMillis(2500))
    .onErrorReturn("Recent board”)
    .take(3)
    .subscribe {
    println(it)
    }
    COMPOSITION & CLEAN CODE
    

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55. Surfboard
    Recent board
    Ironing board
    COMPOSITION & CLEAN CODE
    

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56. val currentBoard = currentBoardServiceMono()
    val recentBoards = recentBoardsServiceFlux()
    return currentBoard.concatWith(recentBoards)
    .map {
    boardService.getName(it)
    }
    .timeout(Duration.ofMillis(2500))
    .onErrorReturn("Recent board”)
    .take(3)
    REAL WORLD EXAMPLE
    

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57. ThreadLocal value = new ThreadLocal<>();
    value.set(42);
    …
    Integer integer = value.get();
    REACTOR GOTCHAS
    

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58. currentUser.concatWith(recentUsers)
    .subscriberContext { sc ->
    sc.put("key", value)
    }
    .flatMap { userId ->
    Mono.subscriberContext().map { sc ->
    userService.getFullName(userId, sc.get("key"))
    }
    }
    .subscribe {
    println(it)
    }
    SUBSCRIBER CONTEXT
    

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59. Get exactly what you want
    Query multiple sources at once, specify what you
    want.
    Strongly typed schema
    Schema is a living documentation.
    Mature web clients
    Clients like Apollo let us remove dependency on
    Redux in ReactJs web apps.
    GraphQL
    

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60. type Query {
    board(id: ID): Board
    }
    type Board {
    id: ID
    name: String
    issues: [Issue]
    }
    type Issue {
    id: ID
    key: String
    }
    SCHEMA
    

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61. POST /jsw/graphql
    query {
    board(id: 42) {
    name
    issues {
    key
    }
    }
    }
    QUERY
    

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62. {
    "data": {
    "board": {
    "name": "Software board”
    "issues": [
    {
    "key": "KEY-1"
    }
    ]
    }
    }
    }
    RESPONSE
    

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63. Project Reactor + GraphQL Java
    OUR SOLUTION
    

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64. DataFetching
    Environment
    Subscriber
    Context
    PROJECT REACTOR GRAPHQL-JAVA
    

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65. Let’s write some code
    GraphQL gateway, Jira Software style
    

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66. GET https://catfact.ninja/fact
    {
    "fact": "The leopard is the most widespread of all big
    cats.",
    "length": 51
    }
    CAT FACTS API
    

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67. GET https://some-random-api.ml/facts/dog
    {
    "fact": "A dogs' first sense to develop is touch."
    }
    DOG FACTS API
    

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68. Cat Facts
    Dog Facts
    

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69. WHY NOT BOTH?
    

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70. POST https://animalfactsgateway.com/grapqhl
    query {
    dog {
    fact
    length
    }
    cat {
    fact
    length
    }
    }
    ANIMAL FACTS GRAPHQL API
    

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71. {
    "data": {
    "dog": {
    "fact": "Dog fact",
    "length": 8
    },
    "cat": {
    "fact": "Cat fact",
    "length": 8
    }
    }
    }
    

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72. dependencies {
    implementation("org.springframework.boot:spring-boot-
    starter-webflux")
    implementation("com.fasterxml.jackson.module:jackson-
    module-kotlin")
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("com.graphql-java:graphql-java:11.0")
    }
    

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73. package com.atlassian.jsw.factsdemo
    import o.s.b.autoconfigure.SpringBootApplication
    import o.s.b.runApplication
    @SpringBootApplication
    class DemoApplication
    fun main(args: Array) {
    runApplication(*args)
    }
    APPLICATION
    

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74. type Query {
    cat: Fact
    dog: Fact
    }
    type Fact {
    fact: String
    length: Int
    }
    GRAPHQL SCHEMA
    

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75. interface FactFetcher: DataFetcher>
    FETCHERS
    public interface DataFetcher {
    T get(DataFetchingEnvironment env) throws Exception;
    }
    

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76. data class Fact(val fact: String, val length: Int)
    FACT CLASS
    

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77. @Component
    class CatFactFetcher(val webClient: WebClient) :
    FactFetcher {
    override fun get(environment:
    DataFetchingEnvironment): CompletionStage =
    webClient.get().uri("https://catfact.ninja/fact")
    .retrieve()
    .bodyToMono(CatFact::class.java)
    .map { Fact(it.fact, it.length) }
    .toFuture()
    }
    data class CatFact(val fact: String, val length: Int)
    CAT FACTS FETCHER
    

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78. @Component
    class DogFactFetcher(val webClient: WebClient) :
    FactFetcher {
    override fun get(environment:
    DataFetchingEnvironment): CompletionStage =
    webClient.get().uri("https://.../facts/dog")
    .retrieve()
    .bodyToMono(DogFact::class.java)
    .map { Fact(it.fact, it.fact.length) }
    .toFuture()
    }
    data class DogFact(val fact: String)
    DOG FACTS FETCHER
    

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79. @Configuration
    class GraphqlConfig {
    @Bean
    fun schema(wiring: RuntimeWiring): GraphQLSchema =
    SchemaGenerator().makeExecutableSchema(
    parseSchema(“/graphql/schema.graphqls"),
    wiring
    )
    }
    GRAPHQL CONFIGURATION
    

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80. @Configuration
    class GraphqlConfig {
    @Bean
    fun factsWiring(
    dogFactFetcher: DogFactFetcher,
    catFactFetcher: CatFactFetcher
    ): RuntimeWiring =
    RuntimeWiring.newRuntimeWiring()
    .type(
    newTypeWiring("Query")
    .dataFetcher("dog", dogFactFetcher)
    .dataFetcher("cat", catFactFetcher)
    )
    .build()
    }
    

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81. override fun processQuery(
    query: String
    ): Mono = Mono.fromFuture(
    GraphQL
    .newGraphQL(graphQLSchema)
    .build()
    .executeAsync(
    ExecutionInput.newExecutionInput()
    .query(query)
    .build()
    )
    )
    SERVICE METHOD
    

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82. @PostMapping(
    path = ["/graphql"],
    consumes = [MediaType.APPLICATION_JSON_VALUE],
    produces = [MediaType.APPLICATION_JSON_VALUE]
    )
    fun graphql(
    @RequestBody body: Map
    ): Mono> {
    val query: String = body["query"] as String? ?: "{}"
    return graphQLService.processQuery(query)
    .map { it.toSpecification() }
    }
    REACTIVE API
    

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83. {
    "data": {
    "dog": {
    "fact": "“Him” and “Her” were the names of President
    Lyndon Johnson's two beagles.",
    "length": 73
    },
    "cat": {
    "fact": "Jaguars are the only big cats that don't
    roar.",
    "length": 46
    }
    }
    }
    RESULT
    

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84. Resilience
    Protect the downstream services from the upstream.
    

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85. 
    250ms 380ms
    380ms
    

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86. CAT FACTS BROKEN
    
    
    
    250ms 30s
    30s
    

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87. {
    "data": {
    "dog": {…},
    "cat": null
    },
    "errors": [
    {
    "message": "Exception while fetching data (/cat) :
    Operation timed out",
    "path": [
    "cat"
    ]
    }
    ]
    }
    

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88. TIMEOUT
    
    
    
    250ms 5000ms
    5000ms
    

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89. class CatFactFetcher(
    val webClient: WebClient
    ) : FactFetcher {
    override fun get(environment:
    DataFetchingEnvironment): CompletionStage =
    webClient.get().uri("https://catfact.ninja/fact")
    .retrieve()
    .bodyToMono(CatFact::class.java)
    .map { … }
    .timeout(Duration.ofMillis(5000))
    .toFuture()
    }
    CAT FACTS WITH TIMEOUT
    

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90. {
    "data": {
    "dog": {…},
    "cat": null
    },
    "errors": [
    {
    "message": "Exception while fetching data (/cat) :
    Did not observe any item or terminal signal within 5000ms
    in 'map' (and no fallback has been configured)",
    "path": [
    “cat"
    ]
    }
    ]
    }
    

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91. CIRCUIT BREAKER
    
    
    
    250ms 0ms
    250ms
    

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92. CIRCUIT BREAKER
    Closed
    Open
    Half-open
    
    
    

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93. class CatFactFetcher(
    val webClient: WebClient,
    val catBreaker: CircuitBreaker
    ) : FactFetcher {
    override fun get(environment:
    DataFetchingEnvironment): CompletionStage =
    webClient.get()

    …
    .timeout(Duration.ofMillis(2500))
    .transform(
    CircuitBreakerOperator.of(catBreaker)
    )
    .toFuture()
    }
    CAT FACTS FETCHER WITH CIRCUIT BREAKER
    

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94. @Bean
    fun catCircuitBreaker(): CircuitBreaker {
    val circuitBreakerConfig =
    CircuitBreakerConfig.custom()
    .ringBufferSizeInClosedState(3)
    .ringBufferSizeInHalfOpenState(3)
    .waitDurationInOpenState(Duration.ofMillis(5000))
    .failureRateThreshold(0.5f)
    .build()
    return circuitBreakerRegistry.circuitBreaker(
    "CatCCB",
    circuitBreakerConfig
    )
    }
    

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95. {
    "data": {
    "dog": {…},
    "cat": null
    },
    "errors": [
    {
    "message": "Exception while fetching data (/cat) :
    CircuitBreaker 'CatCCB' is OPEN and does not permit
    further calls",
    "path": [
    "cat"
    ]
    }
    ]
    }
    

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96. CIRCUIT BREAKER
    
    
    
    250ms 0ms
    250ms
    But we might miss some cat facts.
    

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97. Takeaways
    Even if you forget everything else I said, please try…
    

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98. GraphQL
    For APIs consumed from the front-end.
    Resilience
    To prevent propagating errors downstream.
    Reactive
    For I/O heavy apps.
    Takeaways
    

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99. Beyond Future
    Because you were going to ask about coroutines…
    

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100. GraphQL Java
     There are already pure Kotlin libraries. Spring
     boot has a set of starters too.
     Coroutines
     Support in Spring. New utilities for Project
     reactor.
     Alternatives
     

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101. fun processQuery(query: String): Map
     @PostMapping(
     path = ["/graphql"],
     consumes = [MediaType.APPLICATION_JSON_VALUE],
     produces = [MediaType.APPLICATION_JSON_VALUE]
     )
     fun graphqlCoroutines(
     @RequestBody body: Map
     ): Mono> = mono(Unconfined) {
     val query: String = body["query"] as String? ?: "{}"
     graphQLService.processQuery(query)
     }
     REACTOR WITH COROUTINES
     

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102. Resources
     Write your own reactive and resilient GraphQL gateway in Kotlin
     

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103. 1
     2
     3
     Animal Facts GraphQL Gateway
     https://bitbucket.org/atlassianlabs/animal-facts-graphql-gateway-demo/src/
     master/
     graphql-java
     https://www.graphql-java.com/
     Resilience4j
     https://github.com/resilience4j/resilience4j
     Resources / Code
     

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104. 4 GraphiQL
     https://github.com/graphql/graphiql
     Resources / Code
     5 Coroutines-reactor
     https://github.com/Kotlin/kotlinx.coroutines/tree/master/reactive/kotlinx-coroutines-
     reactor
     

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105. 1
     2
     3
     Kotlin at Trello
     Trello tech blog:

     https://tech.trello.com/kotlin-at-trello/
     Engineering stateless, high-availability cloud services at Atlassian
     Atlassian Engineering Blog:
     https://www.atlassian.com/blog/technology/aws-scaling-multi-region-low-latency-
     service
     More about Micros
     Slightly outdated, but still relevant.

     https://www.youtube.com/watch?v=dc2nqzgqH24
     Resources / Further information
     

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106. 1 Why not both?
     https://knowyourmeme.com/memes/why-not-both-why-dont-we-have-both
     Resources / Other
     2 We are hiring!
     Jira Software is looking for engineers, Java and Kotlin
     http://go.atlassian.com/jsw-hiring
     

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107. MARTIN VARGA | SOFTWARE DEVELOPER | @MARTINTEEVARGA
     Future of Jira Software
     Powered by Kotlin
     

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