Future of Jira Software Powered by Kotlin

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

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kotlinlang.org

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

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

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Not just mobile!

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FUTURE OF JIRA SOFTWARE POWERED BY KOTLIN

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JIRA SOFTWARE?

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Plan, track and release software. JIRA SOFTWARE

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The Story of Jira From the developer’s perspective

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Server Cloud 1001001 0 0 1 0 0 1 0 0 1 0 0 1 1101010 1010101 0 0 1 0 0 1 1110001001 0011110010 1100101011 01111110001 Single Code Base

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Server Cloud 1001001 0 0 1 0 0 1 0 0 1 0 0 1 1101010 1010101 0 0 1 0 0 1

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How Atlassian builds services Making developers productive with platform as a service

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

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MICROS

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

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

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❤

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Experienced with Kotlin. Android Developer Ad

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

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

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

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LATENCY 250ms 250ms 250ms 750ms

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LATENCY 10ms 250ms 10ms 10ms 280ms

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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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val currentUser = "martinId".toMono() MONO

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val recentUsers = listOf("alexId", "bobbieId", "charlieId", "drewId").toFlux() FLUX

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val currentUser = “martinId”.toMono() val recentUsers = listOf("alexId", "bobbieId", "charlieId", "drewId").toFlux() currentUser.concatWith(recentUsers) .map { userService.getFirstName(it) } .take(3) .subscribe { println(it) } COMPOSITION & CLEAN CODE

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Martin Alex Bobbie COMPOSITION & CLEAN CODE

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currentUser.concatWith(recentUsers) .map { userService.getFirstName(it) } .timeout(Duration.ofMillis(2500)) .onErrorReturn("Recent user") .take(3) .subscribe { println(it) } COMPOSITION & CLEAN CODE

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Martin Recent User Bobbie COMPOSITION & CLEAN CODE

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

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

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

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Project Reactor + GraphQL Java OUR SOLUTION

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DataFetching Environment Subscriber Context PROJECT REACTOR GRAPHQL-JAVA

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

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

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Cat Facts Dog Facts

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WHY NOT BOTH?

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

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

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import org.jetbrains.kotlin.gradle.tasks.KotlinCompile plugins { id("org.springframework.boot") version "2.1.6.RELEASE" id("io.spring.dependency-management") version "1.0.7.RELEASE" kotlin("jvm") version "1.2.71" kotlin("plugin.spring") version "1.2.71" } PROJECT DESCRIPTOR

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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") } tasks.withType { kotlinOptions { freeCompilerArgs = listOf("-Xjsr305=strict") jvmTarget = "1.8" } }

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

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

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

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

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

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@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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{ "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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Resilience Protect the downstream services from the upstream.

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250ms 380ms 380ms

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CAT FACTS BROKEN 250ms 30s 30s

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

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TIMEOUT 250ms 5000ms 5000ms

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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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{ "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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CIRCUIT BREAKER 250ms 0ms 250ms

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CIRCUIT BREAKER Closed Open Half-open

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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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@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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{ "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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CIRCUIT BREAKER 250ms 0ms 250ms But we might miss some cat facts.

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

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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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Beyond Future Because you were going to ask about coroutines…

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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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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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Resources Write your own reactive and resilient GraphQL gateway in Kotlin

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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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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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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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1 Why not both? https://knowyourmeme.com/memes/why-not-both-why-dont-we-have-both Resources / Memes

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

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