Future of Jira Software powered by Kotlin - DevFest 2019

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

2. MARTIN VARGA | SOFTWARE DEVELOPER | @MARTINTEEVARGA Future of Jira Software Powered by Kotlin
4. kotlinlang.org
6. Google Pixel 2 Just Black Simply drop your screenshot on to this media placeholder TRELLO MOBILE
7. Jira For cloud and server Confluence For cloud and server OpsGenie Our recent acquisition Not just Trello
8. Not just mobile!
9. FUTURE OF JIRA SOFTWARE POWERED BY KOTLIN
10. JIRA SOFTWARE?
11. Plan, track and release software. JIRA SOFTWARE
13. The Story of Jira From the developer’s perspective
14. 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
15. Server Cloud 1001001 0 0 1 0 0 1 0 0 1 0 0 1 1101010 1010101 0 0 1 0 0 1
16. 1101010 1010101 0 0 1 0 0 1 1101010 1010101 0 0 1 0 0 1
18. 1101010 1010101 0 0 1 0 0 1
19. 11010101010101 0010010101001 00101010111010 1010101010010 0101010010010 10101110101010
20. 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101
22. 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101
23. 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101
24. 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101 010010010101001001010101 110101010101010010010101 001001010101110101010101
25. 1101010101010100 1001010100100101 0101110101010101 010010010101001 0010101011101010 1010101001001010 1001001010101110 1 0 1 0 1 0 1010111 001001
26. 1101010101 010100100 101010010 0101010111 0 1 0 1 0 1 1011100 1 0 0 1 0 1 1 0 1 0 1 0 1010111 001001
27. 1101010 1010101 001001 0 1 0 1 0 1 1011100 1 0 0 1 0 1 1 0 1 0 1 0 1010111 001001 0 1 0 1 0 1 1011100 1 0 0 1 0 1
28. 1101010 1010101 001001 0 1 0 1 0 1 1011100 1 0 0 1 0 1 1 0 1 0 1 0 1010111 001001 0 1 0 1 0 1 1011100 1 0 0 1 0 1
29. 1101010 1010101 001001 0 1 0 1 0 1 1011100 1 0 0 1 0 1
31. How Atlassian builds services Making developers productive with platform as a service
32. PaaS that allows devs to create and deploy a service in matter of minutes. MICROS
33. MICROS
34. name: "animalfacts" compose: animalfacts: image: internal.docker.repo/animalfacts tag: 'PROJECT_VERSION' ports: - 8080:8080 MICROS DESCRIPTOR
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
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.
37. Powered by Kotlin Making developers happy
38. 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
39. Velocity Does it make our developers more productive? Industry Is it already adopted by the developers community? Adopting Kotlin
40. ❤
41. Experienced with Kotlin. Android Developer Ad
42. Experience or interest in Kotlin development. Software Engineer, Developer Productivity, Jira Cloud Ad
43. We happen to have a variety of languages within our stack including Kotlin, Python, and Ruby. Senior Backend Developer Ad
44. A case for a reactive app A real world example of an app that we built recently
45. LATENCY 250ms 250ms 250ms 750ms
46. LATENCY 10ms 250ms 10ms 10ms 280ms
47. 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.
48. val currentBoard = “5”.toMono() MONO 5
49. val recentBoards = listOf("0", "1", "2").toFlux() FLUX 0 1 2
50. 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
51. 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
52. Surfboard Skateboard Ironing board COMPOSITION & CLEAN CODE
53. currentBoard.concatWith(recentBoards) .map { boardService.getName(it) } .timeout(Duration.ofMillis(2500)) .onErrorReturn("Recent board”) .take(3) .subscribe { println(it) } COMPOSITION & CLEAN CODE
54. Surfboard Recent board Ironing board COMPOSITION & CLEAN CODE
55. ThreadLocal<Integer> value = new ThreadLocal<>(); value.set(42); … Integer integer = value.get(); REACTOR GOTCHAS
56. 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
57. 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
58. type Query { board(id: ID): Board } type Board { id: ID name: String issues: [Issue] } type Issue { id: ID key: String } SCHEMA
59. POST /jsw/graphql query { board(id: 42) { name issues { key } } } QUERY
60. { "data": { "board": { "name": "Software board” "issues": [ { "key": "KEY-1" } ] } } } RESPONSE
61. Project Reactor + GraphQL Java OUR SOLUTION
62. DataFetching Environment Subscriber Context PROJECT REACTOR GRAPHQL-JAVA
63. Let’s write some code GraphQL gateway, Jira Software style
64. GET https://catfact.ninja/fact { "fact": "The leopard is the most widespread of all big cats.", "length": 51 } CAT FACTS API
65. GET https://some-random-api.ml/facts/dog { "fact": "A dogs' first sense to develop is touch." } DOG FACTS API
66. Cat Facts Dog Facts
67. WHY NOT BOTH?
68. POST https://animalfactsgateway.com/grapqhl query { dog { fact length } cat { fact length } } ANIMAL FACTS GRAPHQL API
69. { "data": { "dog": { "fact": "Dog fact", "length": 8 }, "cat": { "fact": "Cat fact", "length": 8 } } }
70. 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") }
71. package com.atlassian.jsw.factsdemo import o.s.b.autoconfigure.SpringBootApplication import o.s.b.runApplication @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) } APPLICATION
72. type Query { cat: Fact dog: Fact } type Fact { fact: String length: Int } GRAPHQL SCHEMA
73. interface FactFetcher: DataFetcher<CompletionStage<Fact?>> FETCHERS public interface DataFetcher<T> { T get(DataFetchingEnvironment env) throws Exception; }
74. data class Fact(val fact: String, val length: Int) FACT CLASS
75. @Component class CatFactFetcher(val webClient: WebClient) : FactFetcher { override fun get(environment: DataFetchingEnvironment): CompletionStage<Fact?> = 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
76. @Component class DogFactFetcher(val webClient: WebClient) : FactFetcher { override fun get(environment: DataFetchingEnvironment): CompletionStage<Fact?> = 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
77. @Configuration class GraphqlConfig { @Bean fun schema(wiring: RuntimeWiring): GraphQLSchema = SchemaGenerator().makeExecutableSchema( parseSchema(“/graphql/schema.graphqls"), wiring ) } GRAPHQL CONFIGURATION
78. @Configuration class GraphqlConfig { @Bean fun factsWiring( dogFactFetcher: DogFactFetcher, catFactFetcher: CatFactFetcher ): RuntimeWiring = RuntimeWiring.newRuntimeWiring() .type( newTypeWiring("Query") .dataFetcher("dog", dogFactFetcher) .dataFetcher("cat", catFactFetcher) ) .build() }
79. override fun processQuery( query: String ): Mono<ExecutionResult> = Mono.fromFuture( GraphQL .newGraphQL(graphQLSchema) .build() .executeAsync( ExecutionInput.newExecutionInput() .query(query) .build() ) ) SERVICE METHOD
80. @PostMapping( path = ["/graphql"], consumes = [MediaType.APPLICATION_JSON_VALUE], produces = [MediaType.APPLICATION_JSON_VALUE] ) fun graphql( @RequestBody body: Map<String, Any> ): Mono<Map<String, Any>> { val query: String = body["query"] as String? ?: "{}" return graphQLService.processQuery(query) .map { it.toSpecification() } } REACTIVE API
81. { "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
82. Resilience Protect the downstream services from the upstream.
83. 250ms 380ms 380ms
84. CAT FACTS BROKEN 250ms 30s 30s
85. { "data": { "dog": {…}, "cat": null }, "errors": [ { "message": "Exception while fetching data (/cat) : Operation timed out", "path": [ "cat" ] } ] }
86. TIMEOUT 250ms 5000ms 5000ms
87. class CatFactFetcher( val webClient: WebClient ) : FactFetcher { override fun get(environment: DataFetchingEnvironment): CompletionStage<Fact?> = webClient.get().uri("https://catfact.ninja/fact") .retrieve() .bodyToMono(CatFact::class.java) .map { … } .timeout(Duration.ofMillis(5000)) .toFuture() } CAT FACTS WITH TIMEOUT
88. { "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" ] } ] }
89. CIRCUIT BREAKER 250ms 0ms 250ms
90. CIRCUIT BREAKER Closed Open Half-open
91. class CatFactFetcher( val webClient: WebClient, val catBreaker: CircuitBreaker ) : FactFetcher { override fun get(environment: DataFetchingEnvironment): CompletionStage<Fact?> = webClient.get()
 … .timeout(Duration.ofMillis(2500)) .transform( CircuitBreakerOperator.of(catBreaker) ) .toFuture() } CAT FACTS FETCHER WITH CIRCUIT BREAKER
92. @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 ) }
93. { "data": { "dog": {…}, "cat": null }, "errors": [ { "message": "Exception while fetching data (/cat) : CircuitBreaker 'CatCCB' is OPEN and does not permit further calls", "path": [ "cat" ] } ] }
94. CIRCUIT BREAKER 250ms 0ms 250ms But we might miss some cat facts.
95. Takeaways Even if you forget everything else I said, please try…
96. GraphQL For APIs consumed from the front-end. Resilience To prevent propagating errors downstream. Reactive For I/O heavy apps. Takeaways
97. Beyond Future Because you were going to ask about coroutines…
98. 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
99. fun processQuery(query: String): Map<String, Any> @PostMapping( path = ["/graphql"], consumes = [MediaType.APPLICATION_JSON_VALUE], produces = [MediaType.APPLICATION_JSON_VALUE] ) fun graphqlCoroutines( @RequestBody body: Map<String, Any> ): Mono<Map<String, Any>> = mono(Unconfined) { val query: String = body["query"] as String? ?: "{}" graphQLService.processQuery(query) } REACTOR WITH COROUTINES
100. Resources Write your own reactive and resilient GraphQL gateway in Kotlin
101. 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
102. 4 GraphiQL https://github.com/graphql/graphiql Resources / Code 5 Coroutines-reactor https://github.com/Kotlin/kotlinx.coroutines/tree/master/reactive/kotlinx-coroutines- reactor
103. 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
104. 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
105. MARTIN VARGA | SOFTWARE DEVELOPER | @MARTINTEEVARGA Future of Jira Software Powered by Kotlin