Micronaut with Kotlin Coroutines

Learn how to build microservices with Micronaut.

Transcript

1. Mohit Sarveiya Micronaut with Kotlin Coroutines @heyitsmohit
2. Micronaut with Kotlin Coroutines • Building REST API • Coroutines • Data Access • Circuit breakers • Load Balancing
3. What is Micronaut? • JVM Framework for building microservices • Created by Graham Rose • Polygot - Java, Kotlin or Groovy
4. Benefits • Fast Startup & Small Memory • Meta programming • Reactive • Ahead-of-Time Compilation (AOT)
5. Building Micronaut Project • CLI tool • Intellij • Micronaut Launch
6. Project Creation CLI Tool • Download via SDKMAN • Create scaffolding for app • Create controllers, beans or clients
7. Create Hello World App mn create-app
8. Create Hello World App mn create-app • create-cli-app • create-grpc-app • create-messaging-app
9. Create Hello World App mn create-app -l kotlin • Kotlin • Java • Groovy
10. Create Hello World App mn create-app -l kotlin com.learn.micronautapp Package name
11. Create Hello World App micronautapp src build.gradle Gradle project D Dockerfile
12. Create Hello World App micronautapp src build.gradle D Dockerfile Application.kt
13. Start App fun main(args: Array<String>) { build() .args(*args) .packages("com.learn") .start() }
14. Start App fun main(args: Array<String>) { build() .args(*args) .packages("com.learn") .start() }
15. Hello World REST API GET /greet/{name}
16. Hello World REST API GET /greet/{name} Hello {name}
17. Create Controller mn create-controller
18. Create Controller mn create-controller com.learn.micronautapp.Greeting
19. Create Controller mn create-controller com.learn.micronautapp.Greeting | Rendered controller to src/ ... /GreetingController.kt | Rendered test to src/…/GreetingControllerTest.kt
20. Create Controller mn create-controller com.learn.micronautapp.Greeting | Rendered controller to src/ .
21. Testing @MicronautTest class GreetingControllerTest { 
 }
22. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 }
23. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 @Client("/") interface GreetingClient { } }
24. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 @Client("/") interface GreetingClient { @Get("/greet/{name}") fun greetings(name: String): String } }
25. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 @Inject lateinit var greetingClient: GreetingClient }
26. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 @Test fun `should get greeting`() { val greeting = greetingClient.greetings("Micronaut") } }
27. Testing @MicronautTest class GreetingControllerTest(val embeddedServer: EmbeddedServer) { 
 @Test fun `should get greeting`() { val greeting = greetingClient.greetings("Micronaut") greeting shouldEqual "Greetings Micronaut" } }
28. Controller @Controller class GreetingController { 
 }
29. Controller @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) }
30. Controller @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) }
31. Controller @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) fun greet(name: String): String { } }
32. Controller @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) fun greet(name: String): String { return "Greetings $name" } }
33. GET http: // localhost:8080/greet/micronaut
34. GET http: // localhost:8080/greet/micronaut Port
35. Services HTTP/1.1 200 OK 
 
 content-type: text/plain 
 
 content-length: 19 
 
 connection: keep-alive 
 
 Greetings micronaut 
 GET http: // localhost:8080/greet/micronaut
36. Summary • Create Micronaut Project • Create controller 
 • Unit testing API 

37. Coroutine Support • Suspending functions • Scopes • Dispatchers 
 • Flows 

38. Coroutine Support Micronaut Core RxJava Coroutines
39. Using Coroutines @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) fun greet(name: String): String { return "Greetings $name" } }
40. Using Coroutines @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) suspend fun greet(name: String): String { return "Greetings $name" } }
41. Coroutines Support class Router { 
 Flowable.defer(() -> { if (isKotlinSuspendingFunction) { return executeKotlinSuspendingFunction( ... ); } else { ... } }) }
42. Coroutines Support class Router { 
 Flowable.defer(() -> { if (isKotlinSuspendingFunction) { return executeKotlinSuspendingFunction( ... ); } else { ... } }) }
43. Coroutines Support Publisher executeKotlinSuspendingFunction( ... ) { }
44. Coroutines Support Publisher executeKotlinSuspendingFunction( ... ) { if (isKotlinCoroutineSuspended) { } }
45. Coroutines Support Publisher executeKotlinSuspendingFunction( ... ) { if (isKotlinCoroutineSuspended) { if (isKotlinFunctionReturnTypeUnit) { } else { } } }
46. Coroutines Support Publisher executeKotlinSuspendingFunction( ... ) { if (isKotlinCoroutineSuspended) { if (isKotlinFunctionReturnTypeUnit) { return Completable.fromPublisher( ... ).toFlowable(); } else { } } }
47. Coroutines Support Publisher executeKotlinSuspendingFunction( ... ) { if (isKotlinCoroutineSuspended) { if (isKotlinFunctionReturnTypeUnit) { return Completable.fromPublisher( ... ).toFlowable(); } else { return Publishers.fromCompletableFuture(…); } } }
48. Coroutine Support • Suspending functions • Dispatchers • Scope 
 • Flows 

49. Using Dispatcher @Controller class GreetingController { 
 @Get(uri=“/greet/{name}“) fun greet(name: String): String { return "Greetings $name" } } Use a dispatcher
50. Using Dispatcher @Controller class GreetingController(val executor: ExecutorService) { 
 }
51. Using Dispatcher @Controller class GreetingController(val executor: ExecutorService) { 
 val coroutineDispatcher: CoroutineDispatcher init { coroutineDispatcher = executor.asCoroutineDispatcher() } }
52. Using Dispatcher @Controller class GreetingController(val executor: ExecutorService) { 
 @Get(uri="/greet/{name}") suspend fun greetings(name: String) = 
 withContext(coroutineDispatcher) { } }
53. Coroutine Support • Suspending functions • Dispatchers • Scope 
 • Flows 

54. Creating Scope @Controller class GreetingController(val executor: ExecutorService) { 
 @Get(uri="/greet/{name}") suspend fun greetings(name: String) = coroutineScope { } }
55. Coroutine Support • Suspending functions • Dispatchers • Scope 
 • Flows 

56. Flows Server Client
57. Flows GET /stream
58. Flows @Controller class GreetingController { 
 @Get(uri=“/stream“) fun stream(): Flow<Int> }
59. Flows @Controller class GreetingController { 
 @Get(uri=“/stream“) fun stream(): Flow<Int> = flowOf(1,2,3) .onEach { delay(2000) } }
60. GET http: // localhost:8080/stream
61. GET http: // localhost:8080/stream Services [ {} ]
62. Kotlin / kotlinx.coroutines Code ! Issues Pull Requests kotlinx.coroutines Modules • Reactive • RxJava 2.x • RxJava 3.x
63. Coroutine Support Micronaut Core RxJava Coroutines
64. GET http: // localhost:8080/stream Services HTTP/1.1 200 OK transfer-encoding: chunked [ 1, 2, 3 ]
65. Coroutine Support class FlowConverterRegistrar { @Override public void register( ... ) { addConverter( ... , flow -> Flowable.fromPublisher(ReactiveFlowKt.asPublisher(flow)) ); } }
66. Coroutine Support class FlowConverterRegistrar { @Override public void register( ... ) { addConverter( ... , flow -> Flowable.fromPublisher(ReactiveFlowKt.asPublisher(flow)) ); } }
67. Coroutine Support • Suspending functions • Dispatchers • Scope 
 • Flows 

68. Micronaut with Kotlin Coroutines • Building REST API • Coroutines • Data Access • Circuit breakers • Load Balancing
69. Task REST API GET /tasks/list
70. Task REST API GET /tasks/list GET /tasks/{taskId}
71. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks
72. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks { “id”: taskId “description”: “ ” }
73. Task REST API GET /tasks/list GET /tasks/{taskId} PUT /tasks { “id”: taskId “description”: “ ” } POST /tasks
74. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
75. Data Access Server DB
76. Data Access Server DB Hibernate
77. Data Access data class Task( val id: Long? = null, val description: String = "" )
78. Data Access @Entity data class Task( )
79. Data Access @Entity @Table(name = "task") data class Task( )
80. Data Access data class Task( @Id val id: Long? = null, )
81. Data Access data class Task( @Id @GeneratedValue(strategy = GenerationType.AUTO) val id: Long? = null, )
82. Data Access data class Task( @Column(name = "description", nullable = false, unique = true) val description: String = "" )
83. Data Access DB Task Repo
84. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
85. Data Access class TasksRepository { }
86. Data Access class TasksRepository(val entityManager: EntityManager) { }
87. Data Access class TasksRepository(val entityManager: EntityManager) { fun findById(taskId: Long): Task { } }
88. Data Access class TasksRepository(val entityManager: EntityManager) { fun findById(taskId: Long): Task { return entityManager.find(Task :: class.java, taskId) } }
89. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
90. Data Access class TasksRepository(val entityManager: EntityManager) { fun save(description: String): Task { } }
91. Data Access class TasksRepository(val entityManager: EntityManager) { fun save(description: String): Task { val task = Task(description = description) } }
92. Data Access class TasksRepository(val entityManager: EntityManager) { fun save(description: String): Task { val task = Task(description = description) entityManager.persist(task) return task } }
93. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
94. Data Access class TasksRepository(val entityManager: EntityManager) { fun update(taskId: Long, description: String): Int { } }
95. Data Access class TasksRepository(val entityManager: EntityManager) { fun update(taskId: Long, description: String): Int { val query = "UPDATE Task t SET description = :description where taskId = :taskId" } }
96. Data Access class TasksRepository(val entityManager: EntityManager) { fun update(taskId: Long, description: String): Int { return entityManager.createQuery(sql) }
97. Data Access class TasksRepository(val entityManager: EntityManager) { fun update(taskId: Long, description: String): Int { return entityManager.createQuery(sql) .setParameter(”taskId", taskId) .setParameter(“description", description) .executeUpdate() }
98. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
99. Data Access class TasksRepository(val entityManager: EntityManager) { fun delete(taskId: Long) { val task = findById(taskId) task ?. let { entityManager.remove(it) } } }
100. Data Access DB Task Repo Controller
101. Controller class TaskController { }
102. Controller class TaskController(private val taskRepository: TaskRepository) { }
103. Controller @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { }
104. Controller @ExecuteOn(TaskExecutors.IO) @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { }
105. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
106. Controller @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Get("/{taskId}") fun getTask(taskId: Long): Task? { return taskRepository.findById(taskId) } }
107. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
108. Data Access data class TaskSaveCommand( val description: String )
109. Data Access Controller Client
110. Data Access Controller Client “Task 1”
111. Data Access Controller Client “ ”
112. Data Access Controller Client Validation
113. Data Access data class TaskSaveCommand( @field:NotBlank val description: String )
114. Data Access @Introspected data class TaskSaveCommand( @field:NotBlank val description: String )
115. Data Access @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Post suspend fun save(@Body command: TaskSaveCommand) { } }
116. Data Access @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Post suspend fun save(@Body @Valid command: TaskSaveCommand) { } }
117. Data Access @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Post suspend fun save(@Body @Valid command: TaskSaveCommand) { val task = taskRepository.save(command.description) } }
118. HTTP Response Controller Client 201 OK
119. Micronaut HTTP • Set status code • Update headers • Send errors
120. Data Access @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Post suspend fun save(@Body @Valid command: TaskSaveCommand) { val task = taskRepository.save(command.description) return HttpResponse.created(task) } }
121. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
122. HTTP Response Controller Client Delete taskID
123. HTTP Response Controller Client No content
124. Data Access @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Delete("/{taskId}") fun delete(taskId: Long): HttpResponse<Task> { taskRepository.delete(taskId) return HttpResponse.noContent() } }
125. Task REST API GET /tasks/list GET /tasks/{taskId} POST /tasks PUT /tasks DELETE /tasks/taskId
126. Hibernate In-memory Server DB
127. @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Delete("/{taskId}") fun delete(taskId: Long): HttpResponse<Task> { taskRepository.delete(taskId) return HttpResponse.noContent() } } Services org.hibernate.dialect.Dialect - Using dialect: org.hibernate.dialect.H2Dialect
128. Tasks Project taskapp src build.gradle Configure app D Dockerfile application.yml
129. Configure Database micronaut: application: name: complete datasources: default: url: {JDBC_URL:` ... `} username: ${JDBC_USER:sa} password: ${JDBC_PASSWORD:""} driverClassName: ${JDBC_DRIVER:org.h2.Driver}
130. POST /tasks { “description”: “task1” }
131. HTTP/1.1 201 OK { "id": 1, "description": "task1" } POST /tasks
132. GET /tasks/list [ { "id": 1, "description": "task1" } ]
133. Create Client Server Client
134. CLI Client • Simple client to test APIs • Create Runnable 

135. CLI App mn create-cli-app
136. CLI App mn create-cli-app -l kotlin com.learn.cliapp
137. interface TaskClient { 
 
 @Get("/task/list") fun getTasks(): List<Task> } CLI App
138. interface TaskClient { 
 
 @Get("/task/list") fun getTasks(): List<Task> @Post("/task") fun save(description: String): Task } CLI App
139. class TaskclientCommand : Runnable { @Inject lateinit var taskClient: TaskClient } CLI App
140. class TaskclientCommand : Runnable { fun run() { taskClient.getTasks() .forEach { println(it) } } CLI App
141. Summary • Setup Controller for REST API • HTTP Requests & Responses • Data Access • Create Client 

142. Micronaut with Kotlin Coroutines • Building REST API • Coroutines • Data Access • Circuit breakers • Load Balancing
143. Controller @Controller("/tasks") class TaskController(val taskRepository: TaskRepository) { @Get(“/list") fun list(): List<Task> { } } Exception
144. Circuit Breaker • # of Retries • Delay 

145. @CircuitBreaker(delay="1s", attempts = "5") interface TaskClient { 
 } CLI App
146. Micronaut with Kotlin Coroutines • Building REST API • Coroutines • Data Access • Circuit breakers • Load Balancing
147. Load Balancing Server Client Server Server
148. Tasks Project taskapp src build.gradle Configure app D Dockerfile application.yml
149. Tasks Project consul: client: registration: enabled: true default-zone: "${CONSUL_HOST:localhost}:${CONSUL_PORT:8500}"
150. @Controller("/tasks") class TaskController(private val taskRepository: TaskRepository) { @Delete("/{taskId}") fun delete(taskId: Long): HttpResponse<Task> { taskRepository.delete(taskId) return HttpResponse.noContent() } } Services Registered service with Consul io.micronaut.runtime.Micronaut - Server Running: http: // localhost:44004
151. Load Balancing Server Client Server Server
152. Micronaut with Kotlin Coroutines • Building REST API • Coroutines • Data Access • Circuit breakers • Load Balancing
153. Resources • Introduction to Micronaut • Graeme Rocher 
 • Talk on coroutines! 
 
 https: // codingwithmohit.com/talks/
154. Thank You! www.codingwithmohit.com @heyitsmohit