Serverless 近年來成為當紅詞彙，其部署快速、彈性擴充、依用量計費等屬性，深深打中特定應用情境的需求，各家程式語言及平台無不推出對應的框架及服務來回應這樣的市場。在這股浪潮下，Kotlin 當然也不會缺席！在這場分享裡，首先概述 Serverless 的基本特性，並盤點現有開發生態系裡可選的工具有哪些。接著，將示範如何以 Serverless 架構快速打造一個 Web Service。期能透過本場分享，讓大家看到 Kotlin 在 Serverless 領域的運用方式及潛力，以及在哪些情境下 Serverless 是一個適切的選擇。

1. otlin
Serverless
(Shengyou Fan)
JCConf 2020
2020/11/19
Photo by Cam Adams on Unsplash

2. —
• Serverless
• FaaS Kotlin
• Kotless
•

3. —
Develop Build/Pack Deploy Scale Up

4. Operation …
!
Kotlin

5. Serverless
—
from Wikipedia
Serverless computing is a cloud computing execution
model in which the cloud provider runs the server,
and dynamically manages the allocation of machine
resources.
Serverless

6. —
Image source: Serverless Development With Kotlin and Kotless by Vlaadislav Tankov

7. Serverless
—
•
•
•
•

8. FaaS Java
—

9. Kotlin
"
Kotlin

10. —
?query=param
①
②
③
④
Client
FaaS
Local Development
Kotlin Functions

11. HTTP Request
—
GET http://localhost:8001/?amount={n}
Accept: application/json
1. n Contact
2. JSON

12. HTTP Response
—
{
"data": [
{
"id": ...,
"name": "...",
"email": "...",
"createdAt": "yyyy-MM-dd HH:mm:ss.nnnnnn",
"updatedAt": "yyyy-MM-dd HH:mm:ss.nnnnnn"
},
// ...
]
}
1. n
2. JSON
3. data

13. Data Class
—
// Data Class
data class Contact(
val id: Long?,
val name: String,
val email: String,
val createdAt: String,
val updatedAt: String
)
// JSON
{
"id": 1,
"name": "...",
"email": "...",
"createdAt": "yyyy-MM-dd HH:mm:ss.nnnnnn",
"updatedAt": "yyyy-MM-dd HH:mm:ss.nnnnnn"
}
• JSON Data Class

14. class ContactService() {
// ...
@ExperimentalTime
fun generate(amount: Int = 10): List<Contact> {
return (1..amount).map {
Contact(
// ...
)
}
}
}
Service Class
—
Service
• javafaker datetime
serilization library
•
•

15. JetBrains Package Search
—

16. Packages Tool Window
—
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id paulo vituperata, nam laoreet luptatum delicatissimi id. Fugit primis ullamcorper no qui,
nusquam accusamus temporibus sit ad.
Vis iudico commodo ne, ad eam quas legimus, esse dicant explicari has in. Eum ocurreret
interesset appellantur ei, quo cu timeam euismod laoreet. Per ne nisl justo. An vel laboramus
efficiantur deterruisset, nec ne mandamus scripserit, vix id rebum dicta dictas. Mel suscipit
periculis similique in.

17. // build.gradle
dependencies {
implementation "com.github.javafaker:javafaker:1.0.2"
}
// io.kraftsman.services.ContactService
val faker = Faker(Locale("en"))
Contact(
id = it.toLong(),
name = faker.name().fullName(),
email = faker.internet().emailAddress(),
createdAt = ...,
updatedAt = ...
)
Java Faker
—
• Java Faker
• Faker

18. kotlinx.datetime
• repository
•
// build.gradle
repositories {
maven { url "https://kotlin.bintray.com/kotlinx/" }
}
dependencies {
implementation "org.jetbrains.kotlinx:kotlinx-datetime:$ver"
}
// io.kraftsman.services.ContactService
val current = Clock.System.now()
val tz = TimeZone.of("Asia/Taipei")
Contact(
// ...
createdAt = current
.toLocalDateTime(tz).toString(),
updatedAt = (current + x.hours + y.minutes)
.toLocalDateTime(tz).toString()
)
Datetime
—
kotlinx.datetime
•
•
• (x + y )
•

19. // build.gradle
plugins {
id 'org.jetbrains.kotlin.plugin.serialization' version '1.4.10'
}
repositories {
jcenter()
}
dependencies {
implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:$ver"
}
• Gradle Plugin
Serialization (pt.1)
—
• Repository
•

20. // io.kraftsman.dtos.Contact
@Serializable
data class Contact(
// ...
)
// io.kraftsman.functions.Handler
val contacts: List<Contact> = ContactService().generate(amount)
Json.encodeToString(
mapOf("data" to contacts)
)
Serialization (pt.2)
—
• Annotation
JSON
• List Map data
• Map JSON

21. Cloud Functions
—
• IntelliJ IDEA
• JDK 11
• gcloud CLI
Repository: https://github.com/shengyou/gcp-cloud-functions-kotlin

22. $ brew cask install google-cloud-sdk
$ gcloud auth login
$ gcloud projects list
$ gcloud config set project PROJECT_ID
/ gcloud
—
• gcloud CLI
• GCP
• GCP Project
• GCP Project

23. 1. Kotlin
2. Gradle
3. JDK 11
—

24. configurations {
invoker
}
dependencies {
implementation "...:functions-framework-api:$ver"
invoker "...:java-function-invoker:$ver"
}
tasks.register("runFunction", JavaExec) {
main = '...'
classpath(configurations.invoker)
inputs.files(..., ...)
args(
'--target', ...Property('runFunction.target') ?: '',
'--port', ...Property('runFunction.port') ?: ...
)
doFirst {
args('--classpath', ...)
}
}
Gradle
—
Cloud Function
• functions-framework-api
• java-function-invoker
Gradle Task
$ gradle runFunction
Java Invoker

25. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
}
}
Handler
—
• Class
• HttpFunction (
functions-framework-api)
• service()
• req res

26. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
val param = request.getFirstQueryParameter("amount")
.orElse("")
val amount = param.toIntOrNull() ?: 10
}
}
Query
—
• HttpRequest Query
•

27. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
val param = request.getFirstQueryParameter("amount")
.orElse("")
val amount = param.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
}
}
/
—
• Service
• JSON

28. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
val param = request.getFirstQueryParameter("amount")
.orElse("")
val amount = param.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
with(res) {
setStatusCode(HttpURLConnection.HTTP_OK)
setContentType("application/json")
writer.write(jsonString)
}
}
}
Response
—
• HTTP Status Code
• Content-Type
• JSON

29. $ ./gradlew runFunction
-PrunFunction.target=CLASS
-PrunFunction.port=PORT
—
• Gradle Task
• Run Configuration

30. $ gcloud functions deploy PUBLIC_PATH
--region REGION
--runtime java11
--trigger-http
--memory 256MB
--entry-point ENTRY_POINT_CLASS
--allow-unauthenticated
—
• gcloud

31. Azure Functions
—
• IntelliJ IDEA + Plugins
• JDK 8
• Azure CLI
• Azure Functions Core Tools
Repository: https://github.com/shengyou/microsoft-azure-functions-kotlin

32. $ brew update
$ brew install azure-cli
$ az login
$ az account -a SUBSCRIPTION_ID
$ brew tap azure/functions
$ brew installazure-function-core-tools@3
—
• Azure CLI
• Azure
• Azure Functions Core Tools
• Azure Toolkit for IntelliJ

33. 1. Azure Functions
2. Gradle
3. JDK 8
—

34. 1. Azure Functions
2. Gradle
3. JDK 8
Kotlin
— ①
②
③
④

35. 1. Project
2. Class
3.
Kotlin Class
—

36. class Handler {
@FunctionName("...")
fun run(
@HttpTrigger(
name = "...",
route = "...",
methods = [HttpMethod.GET],
authLevel = AuthorizationLevel.ANONYMOUS
)
request: HttpRequestMessage<Optional<String?>>,
context: ExecutionContext
): HttpResponseMessage {
// ...
}
}
Handler
—
• Class Method
• Annotation
• route methods
• request context

37. class Handler {
@FunctionName("...")
fun run(/* . . . */): HttpResponseMessage {
val query = request.queryParameters["amount"]
val amount = query?.toIntOrNull() ?: 10
}
}
Query
—
• request Query
•

38. class Handler {
@FunctionName("...")
fun run(/* . . . */): HttpResponseMessage {
val query = request.queryParameters["amount"]
val amount = query?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
}
}
/
—
• Service
• JSON

39. class Handler {
@FunctionName("...")
fun run(/* . . . */): HttpResponseMessage {
val query = request.queryParameters["amount"]
val amount = query?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
return request.createResponseBuilder(HttpStatus.OK)
.header("Content-Type", "application/json")
.body(jsonString)
.build()
}
}
Response
—
• HTTP Status Code
• Content-Type
• JSON

40. —
• Gradle Task

41. azurefunctions {
subscription = '...'
resourceGroup = '...'
appName = '...'
pricingTier = 'Consumption'
region = '...'
runtime {
os = 'linux'
}
authentication {
type = 'azure_cli'
}
}
—
• Azure Gradle
• Gradle Task

42. AWS Lambda
—
• IntelliJ IDEA + Plugin
• JDK 11
• Docker
• AWS CLI
• AWS SAM CLI
Repository: https://github.com/shengyou/amazon-lambda-kotlin

43. $ brew update
$ brew install awscli
$ aws configure
$ aws sts get-caller-identity
$ brew tap aws/tap
$ brew install aws-sam-cli
—
• AWS CLI
• AWS
• Account ID
• IAM (User & Role)
• AWS SAM CLI
• AWS Toolkit

44. 1. Kotlin
2. Gradle
3. JDK 11
—
1. AWS

45. plugins {
id 'java'
id 'com.github.johnrengelman.shadow' version '6.1.0'
}
dependencies {
implementation "...:aws-lambda-java-core:1.2.1"
implementation "...:aws-lambda-java-events:3.1.0"
runtimeOnly "...:aws-lambda-java-log4j2:1.2.0"
}
Gradle
—
AWS Lambda
• aws-lambda-java-core
• aws-lambda-java-events
• aws-lambda-java-log4j2
Gradle Plugin
• java
• shadow

46. class Handler : RequestHandler <
APIGatewayProxyRequestEvent,
APIGatewayProxyResponseEvent
> {
@Throws(IOException::class)
override fun handleRequest(
request: APIGatewayProxyRequestEvent,
context: Context
): APIGatewayProxyResponseEvent {
// ...
}
}
Handler
—
• Class Method
• RequestHandler ( aws-
lambda-java-core)
• Handler Method
• reqest context

47. class Handler : RequestHandler <...> {
@Throws(IOException::class)
override fun method(/* ... */): ...ResponseEvent {
val param = request.queryStringParameters["amount"]
val amount = param?.toIntOrNull() ?: 10
}
}
Query
—
• request Query
•

48. class Handler : RequestHandler <...> {
@Throws(IOException::class)
override fun method(/* ... */): ...ResponseEvent {
val param = request.queryStringParameters["amount"]
val amount = param?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
}
}
/
—
• Service
• JSON

49. class Handler : RequestHandler <...> {
@Throws(IOException::class)
override fun method(/* ... */): ...ResponseEvent {
val param = request.queryStringParameters["amount"]
val amount = param?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val jsonString = Json.encodeToString(
mapOf("data" to contacts)
)
return APIGatewayProxyResponseEvent()
.withStatusCode(HttpURLConnection.HTTP_OK)
.withHeaders(
mapOf("Content-Type" to "application/json")
)
.withBody(jsonString)
}
}
Response
—
• HTTP Status Code
• Content-Type
• JSON

50. $ aws lambda create-function --function-name NAME
--zip-file fileb://build/libs/SHADOWJAR.jar
--handler CLASS::METHOD
--runtime java11
--timeout 15
--memory-size 128
--role ROLE
—
• aws
• AWS Console

51. API Gateway
—
• Trigger

52. JDK 11 8 11
IntelliJ Plugin ✗ ✓ ✓
Gradle ✓ ✓
Framework ✓ ✓ ✓
+
—

53. #
…
Cloud Configuration
Vendor Lock-in…

54. Kotless
—
https://site.kotless.io/
• Serverless Framework
• Kotless DSL
• Gradle Plugin
• Developed by Vladislav Tankov
from JetBrains
• Open Source (Apache 2.0)

55. —
Image source: Serverless Development With Kotlin and Kotless by Vlaadislav Tankov

56. 1. Kotlin
2. Gradle Kotlin ❤
3. JDK 11
—

57. plugins {
kotlin("jvm") version "1.3.72" apply true
kotlin("plugin.serialization") version "1.3.72"
id("io.kotless") version "0.1.6" apply true
}
dependencies {
implementation("io.kotless", "kotless-lang", "0.1.6")
}
Gradle
—
Gradle Plugins
• Kotlin 1.3.72
• Serialization 1.3.72
• Kotless 0.1.6
• Kotless

58. @Get("/")
fun handler(): HttpResponse {
val dom = """
// ...
""".trimIndent()
return html(dom)
}
Function
—
• Function
• Annotation Route
• HttpResponse

59. @Get("/...")
fun handler(): HttpResponse {
val param = KotlessContext.HTTP.request.params?.get("amount")
val amount = param?.toIntOrNull() ?: 10
}
Query
—
• KotlessContext Query
•

60. @Get("/...")
fun handler(): HttpResponse {
val param = KotlessContext.HTTP.request.params?.get("amount")
val amount = param?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val json = Json(JsonConfiguration.Stable)
val jsonString = json.stringify(
Contact.serializer(), contacts
)
}
/
—
• Service
• JSON

61. @Get("/...")
fun handler(): HttpResponse {
val param = KotlessContext.HTTP.request.params?.get("amount")
val amount = param?.toIntOrNull() ?: 10
val contacts = ContactService().generate(amount)
val json = Json(JsonConfiguration.Stable)
val jsonString = json.stringify(
Contact.serializer(), contacts
)
return json(jsonString)
}
Response
—
• JSON

62. —
• Gradle Task

63. kotless {
config {
bucket = "..."
terraform {
profile = "..."
region = "..."
}
}
}
—
• AWS CLI Credentials
• S3 Bucket
• AWS Gradle
• Gradle Task

64. #
…
Serverless

65. Kotless
—
Image source: Serverless Development With Kotlin and Kotless by Vlaadislav Tankov

66. 1. Ktor (1.3.2)
2. Gradle Kotlin ❤
3. JDK 11
4. Server Features
• Routing
• ContentNegotiation
• Jackson
Ktor
—

67. plugins {
id("io.kotless") version "0.1.6" apply true
}
dependencies {
// ...
implementation("io.ktor:ktor-server-netty:$ktor_version")
// ...
implementation("io.kotless", "ktor-lang", “0.1.6")
// ...
}
Gradle
—
Gradle Plugins
• Kotless 0.1.6
• Netty
• Kotless for Ktor

68. class Server : Kotless() {
override fun prepare(app: Application) {
app.install(ContentNegotiation) {
jackson {
enable(SerializationFeature.INDENT_OUTPUT)
}
}
app.routing {
// ...
}
}
}
Kotless App
—
Kotless App
• Kotless
• prepare()
• Ktor app

69. // Application.kt
@Suppress("unused")
@kotlin.jvm.JvmOverloads
fun Application.module(testing: Boolean = false) {
// ...
}
// resources/application.conf
ktor {
deployment {
port = 8080
port = ${?PORT}
}
application {
modules = [ io.kraftsman.Server.prepare ]
}
}
—
• Application.kt
•

70. Roadmap
—
Image source: Serverless Development With Kotlin and Kotless by Vlaadislav Tankov

71. % & %
Repository: https://github.com/shengyou/jetbrains-kotless-framework
Repository: https://github.com/shengyou/jetbrains-ktor-with-kotless

72. —
• Serverless
• Kotlin Serverless
• Kotless Framework
• Kotless

73. Serverless
—
• IBM Bluemix
• Cloudflare Workers
• Alibaba Cloud
• Huawei Cloud
• …

74. Serverless
—
• Fat Jar
• Container
• Kotlin/JS

75. Serverless
—
• Spring Cloud Function
• Micronaut
• Osiris
• Nimbus
• …

76. —
• Mobile Backend (API …)
• Webhook ( API …)
• ( …)

77. —
•
•
•
•
Image source: The Definition of Framework by Francesco Strazzullo

78. https://tw.kotlin.tips
Tips
—
https://tw.intellij.tips

79. —
Coding
Kraftsman

80. (Shengyou Fan)
shengyou.fan@jetbrains.com
Q&A
—
otlin
Serverless