feat(backend): add NATS

backend/Dockerfile

@@ -4,6 +4,8 @@ ARG SERVICE_NAME
 WORKDIR /app
 
 COPY ./$SERVICE_NAME ./$SERVICE_NAME
+COPY ./common ./common
+COPY ./protobuf ./protobuf
 COPY ./gradle ./gradle
 COPY ./gradle.properties .
 COPY ./gradlew .

backend/api_gateway/build.gradle.kts

@@ -21,11 +21,14 @@ repositories {
 }
 
 dependencies {
-    implementation("org.springframework.boot:spring-boot-starter-actuator:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-oauth2-resource-server:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-security:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-validation:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-web:3.1.5")
+    implementation(project(":common"))
+    implementation(project(":protobuf"))
+    implementation("org.springframework.boot:spring-boot-starter-actuator")
+    implementation("org.springframework.boot:spring-boot-starter-oauth2-resource-server")
+    implementation("org.springframework.boot:spring-boot-starter-security")
+    implementation("org.springframework.boot:spring-boot-starter-validation")
+    implementation("org.springframework.boot:spring-boot-starter-web")
+    implementation("io.nats:jnats:2.17.1")
     developmentOnly("org.springframework.boot:spring-boot-devtools")
     testImplementation("org.springframework.boot:spring-boot-starter-test")
     testImplementation("org.springframework.boot:spring-boot-testcontainers")

backend/api_gateway/src/main/kotlin/com/linkedout/backend/ApiGatewayApplication.kt

@@ -3,7 +3,7 @@ package com.linkedout.backend
 import org.springframework.boot.SpringApplication
 import org.springframework.boot.autoconfigure.SpringBootApplication
 
-@SpringBootApplication
+@SpringBootApplication(scanBasePackages = ["com.linkedout"])
 open class ApiGatewayApplication
 
 fun main(args: Array<String>) {

backend/api_gateway/src/main/kotlin/com/linkedout/backend/controller/JobsController.kt

@@ -0,0 +1,16 @@
+package com.linkedout.backend.controller
+
+import com.linkedout.backend.model.Job
+import com.linkedout.backend.service.JobService
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RequestMapping
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+@RequestMapping("/api/v1/jobs")
+open class JobsController(private val jobService: JobService) {
+    @GetMapping
+    open fun getJobs(): List<Job> {
+        return jobService.findAll()
+    }
+}

backend/api_gateway/src/main/kotlin/com/linkedout/backend/model/Job.kt

@@ -0,0 +1,7 @@
+package com.linkedout.backend.model
+
+data class Job(
+    val id: String,
+    val title: String,
+    val category: String
+)

backend/api_gateway/src/main/kotlin/com/linkedout/backend/service/JobService.kt

@@ -0,0 +1,27 @@
+package com.linkedout.backend.service
+
+import com.linkedout.backend.model.Job
+import com.linkedout.common.service.NatsService
+import com.linkedout.common.utils.RequestResponseFactory
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.stereotype.Service
+
+@Service
+class JobService(private val natsService: NatsService, @Value("\${app.services.jobs.subjects.findAll}") private val findAllSubject: String) {
+    fun findAll(): List<Job> {
+        // Request jobs from the jobs service
+        val response = natsService.requestWithReply(findAllSubject, RequestResponseFactory.newRequest().build())
+
+        // Handle the response
+        if (!response.hasGetJobsResponse()) {
+            throw Exception("Invalid response")
+        }
+
+        val getJobsResponse = response.getGetJobsResponse()
+
+        return getJobsResponse.jobsList
+            .map { job ->
+                Job(job.id, job.title, job.category)
+            }
+    }
+}

backend/api_gateway/src/main/resources/application.yml

@@ -7,3 +7,14 @@ spring:
 
 server:
   port: 9090
+
+nats:
+  timeout: 1000
+  spring:
+    server: nats://localhost:4222
+
+app:
+  services:
+    jobs:
+      subjects:
+        findAll: jobs.findAll

backend/common/build.gradle.kts

@@ -0,0 +1,47 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.springframework.boot.gradle.tasks.bundling.BootJar
+
+plugins {
+    `java-library`
+    id("org.springframework.boot")
+    id("io.spring.dependency-management")
+    id("org.jlleitschuh.gradle.ktlint")
+    kotlin("jvm")
+    kotlin("plugin.spring")
+    kotlin("plugin.jpa")
+}
+
+group = "com.linkedout"
+version = "1.0.0-SNAPSHOT"
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_17
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation(project(":protobuf"))
+    implementation("org.springframework.boot:spring-boot-starter")
+    implementation("org.springframework:spring-messaging")
+    implementation("io.nats:jnats:2.17.1")
+    implementation("com.google.protobuf:protobuf-kotlin:3.25.0")
+    testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+    kotlinOptions {
+        freeCompilerArgs += "-Xjsr305=strict"
+        jvmTarget = "17"
+    }
+}
+
+tasks.withType<Test> {
+    useJUnitPlatform()
+}
+
+tasks.getByName<BootJar>("bootJar") {
+    enabled = false
+}

backend/common/src/main/kotlin/com/linkedout/common/service/NatsService.kt

@@ -0,0 +1,28 @@
+package com.linkedout.common.service
+
+import com.linkedout.proto.RequestOuterClass.Request
+import com.linkedout.proto.ResponseOuterClass.Response
+import io.nats.client.Connection
+import io.nats.client.Nats
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.context.annotation.Lazy
+import org.springframework.stereotype.Service
+import java.time.Duration
+
+@Service
+@Lazy
+class NatsService(@Value("\${nats.spring.server}") private val natsUrl: String, @Value("\${nats.timeout}") private val natsTimeout: Long) {
+    val nc: Connection = Nats.connect(natsUrl)
+    val timeout: Duration = Duration.ofMillis(natsTimeout)
+
+    fun requestWithReply(subject: String, request: Request): Response {
+        val rawResponse = nc.request(subject, request.toByteArray(), timeout)
+        val response = Response.parseFrom(rawResponse.data)
+
+        if (!response.success) {
+            throw Exception(response.errorMessage)
+        }
+
+        return response
+    }
+}

backend/common/src/main/kotlin/com/linkedout/common/stream/converter/ConverterConfiguration.kt

@@ -0,0 +1,18 @@
+package com.linkedout.common.stream.converter
+
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import org.springframework.messaging.converter.MessageConverter
+
+@Configuration
+class ConverterConfiguration {
+    @Bean
+    fun requestConverter(): MessageConverter {
+        return RequestConverter()
+    }
+
+    @Bean
+    fun responseConverter(): MessageConverter {
+        return ResponseConverter()
+    }
+}

backend/common/src/main/kotlin/com/linkedout/common/stream/converter/RequestConverter.kt

@@ -0,0 +1,17 @@
+package com.linkedout.common.stream.converter
+
+import com.linkedout.proto.RequestOuterClass
+import org.springframework.messaging.Message
+import org.springframework.messaging.converter.AbstractMessageConverter
+import org.springframework.util.MimeType
+
+class RequestConverter : AbstractMessageConverter(MimeType("application", "vnd.linkedout.proto-request")) {
+    override fun supports(clazz: Class<*>): Boolean {
+        return RequestOuterClass.Request::class.java == clazz
+    }
+
+    override fun convertFromInternal(message: Message<*>, targetClass: Class<*>, conversionHint: Any?): Any? {
+        val payload = message.payload
+        return payload as? RequestOuterClass.Request ?: RequestOuterClass.Request.parseFrom(payload as ByteArray)
+    }
+}

backend/common/src/main/kotlin/com/linkedout/common/stream/converter/ResponseConverter.kt

@@ -0,0 +1,16 @@
+package com.linkedout.common.stream.converter
+
+import com.linkedout.proto.ResponseOuterClass
+import org.springframework.messaging.MessageHeaders
+import org.springframework.messaging.converter.AbstractMessageConverter
+import org.springframework.util.MimeType
+
+class ResponseConverter : AbstractMessageConverter(MimeType("application", "vnd.linkedout.proto-response")) {
+    override fun supports(clazz: Class<*>): Boolean {
+        return ResponseOuterClass.Response::class.java == clazz
+    }
+
+    override fun convertToInternal(payload: Any, headers: MessageHeaders?, conversionHint: Any?): Any? {
+        return (payload as ResponseOuterClass.Response).toByteArray()
+    }
+}

backend/common/src/main/kotlin/com/linkedout/common/utils/RequestResponseFactory.kt

@@ -0,0 +1,25 @@
+package com.linkedout.common.utils
+
+import com.linkedout.proto.RequestOuterClass
+import com.linkedout.proto.ResponseOuterClass
+import java.util.UUID
+
+class RequestResponseFactory private constructor() {
+    companion object {
+        fun newRequest(): RequestOuterClass.Request.Builder {
+            return RequestOuterClass.Request.newBuilder()
+                .setRequestId(UUID.randomUUID().toString())
+        }
+
+        fun newSuccessfulResponse(): ResponseOuterClass.Response.Builder {
+            return ResponseOuterClass.Response.newBuilder()
+                .setSuccess(true)
+        }
+
+        fun newFailedResponse(message: String): ResponseOuterClass.Response.Builder {
+            return ResponseOuterClass.Response.newBuilder()
+                .setSuccess(false)
+                .setErrorMessage(message)
+        }
+    }
+}

backend/jobs/build.gradle.kts

@@ -21,19 +21,26 @@ repositories {
 }
 
 dependencies {
-    implementation("org.springframework.boot:spring-boot-starter-actuator:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-data-r2dbc:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-validation:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-webflux:3.1.5")
-    implementation("org.springframework.boot:spring-boot-starter-web:3.1.5")
-    implementation("org.springframework:spring-jdbc:6.0.13")
+    implementation(project(":common"))
+    implementation(project(":protobuf"))
+    implementation("org.springframework.boot:spring-boot-starter-actuator")
+    implementation("org.springframework.boot:spring-boot-starter-data-r2dbc")
+    implementation("org.springframework.boot:spring-boot-starter-validation")
+    implementation("org.springframework.boot:spring-boot-starter-webflux")
+    implementation("org.springframework.boot:spring-boot-starter-web")
+    implementation("org.springframework:spring-jdbc")
+    implementation("org.springframework.cloud:spring-cloud-stream:4.0.4")
+    implementation("io.nats:jnats:2.17.1")
+    implementation("io.nats:nats-spring:0.5.6")
+    implementation("io.nats:nats-spring-cloud-stream-binder:0.5.3")
     implementation("org.flywaydb:flyway-core:9.22.3")
     implementation("org.postgresql:r2dbc-postgresql:1.0.2.RELEASE")
     implementation("jakarta.validation:jakarta.validation-api:3.0.2")
     implementation("org.jetbrains.kotlin:kotlin-reflect:1.9.20")
     developmentOnly("org.springframework.boot:spring-boot-devtools")
     runtimeOnly("org.postgresql:postgresql")
     testImplementation("org.springframework.boot:spring-boot-starter-test")
+    testImplementation("org.springframework.cloud:spring-cloud-stream-test-binder:4.0.4")
 }
 
 tasks.withType<KotlinCompile> {

backend/jobs/src/main/kotlin/com/linkedout/jobs/JobsApplication.kt

@@ -3,7 +3,7 @@ package com.linkedout.jobs
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.runApplication
 
-@SpringBootApplication
+@SpringBootApplication(scanBasePackages = ["com.linkedout"])
 class JobsApplication
 
 fun main(args: Array<String>) {