Support OpenTelemetry to trace flow executions

Hands down one of the coolest things I've ever done

Author: SIMULATAN

api/build.gradle.kts

@@ -15,6 +15,8 @@ dependencies {
     implementation(ktor.server.auth.jwt)
     api(libraries.bson.kotlinx)
     api(database.mongodb)
+    api(monitoring.opentelemetry.api)
+    api(monitoring.opentelemetry.context)
 
     implementation(tests.junit.api)
 }

api/src/main/kotlin/me/snoty/backend/config/Config.kt

@@ -3,7 +3,7 @@ package me.snoty.backend.config
 data class Config(
 	val mongodb: MongoConfig,
 	val port: Short = 8080,
-	val monitoringPort: Short = 9090,
+	val monitoringPort: Short = 9000,
 	val publicHost: String,
 	val environment: Environment,
 	val authentication: OidcConfig,

api/src/main/kotlin/me/snoty/backend/observability/OpenTelemetrySemconv.kt

@@ -0,0 +1,7 @@
+package me.snoty.backend.observability
+
+import io.opentelemetry.api.common.AttributeKey
+
+// https://github.com/open-telemetry/semantic-conventions/pull/731
+val USER_ID = AttributeKey.stringKey("user.id")
+val JOB_ID = AttributeKey.stringKey("job.id")

api/src/main/kotlin/me/snoty/backend/observability/OpenTelemetryUtils.kt

@@ -0,0 +1,37 @@
+package me.snoty.backend.observability
+
+import io.opentelemetry.api.OpenTelemetry
+import io.opentelemetry.api.common.AttributeKey
+import io.opentelemetry.api.trace.Span
+import io.opentelemetry.api.trace.SpanBuilder
+import io.opentelemetry.api.trace.StatusCode
+import io.opentelemetry.api.trace.Tracer
+import io.opentelemetry.api.trace.TracerProvider
+import io.opentelemetry.context.Context
+import org.bson.Document
+import java.util.UUID
+import kotlin.reflect.KClass
+
+fun OpenTelemetry.getTracer(clazz: KClass<*>): Tracer
+	= getTracer(clazz.java.`package`.specificationTitle)
+
+fun TracerProvider.getTracer(clazz: KClass<*>): Tracer
+	= get(clazz.java.`package`.specificationTitle)
+
+context(Tracer)
+fun Span.subspan(name: String, builder: SpanBuilder.() -> Unit): Span
+	= this@Tracer.spanBuilder(name)
+		.also(builder)
+		.apply {
+			setParent(Context.current().with(this@subspan))
+		}
+		.startSpan()
+
+
+fun SpanBuilder.setAttribute(key: String, value: Document) = this.setAttribute(key, value.toJson())
+fun SpanBuilder.setAttribute(key: AttributeKey<String>, value: UUID) = this.setAttribute(key, value.toString())
+
+fun Span.setException(e: Throwable) {
+	this.setStatus(StatusCode.ERROR)
+	this.recordException(e)
+}

build.gradle.kts

@@ -26,6 +26,7 @@ val isDevelopment: Boolean = project.findProperty("me.snoty.development")?.toStr
 allprojects {
     repositories {
         mavenCentral()
+        maven("https://maven.simulatan.me/releases")
     }
 
     tasks.withType<KotlinCompile>().configureEach {
@@ -85,6 +86,7 @@ testing {
                 implementation(tests.testcontainers.junit)
                 implementation(tests.testcontainers.keycloak)
                 implementation(tests.testcontainers.mongodb)
+                implementation(monitoring.opentelemetry.testing)
                 implementation(devSourceSet.output)
 
                 runtimeOnly(tests.junit.engine)
@@ -140,6 +142,11 @@ dependencies {
     implementation(monitoring.ktor.opentelemetry)
     implementation(monitoring.ktor.server.metricsMicrometer)
     implementation(monitoring.micrometer.prometheus)
+    implementation(monitoring.opentelemetry.api)
+    implementation(monitoring.opentelemetry.context)
+    implementation(monitoring.opentelemetry.semconv)
+    implementation(monitoring.opentelemetry.kotlin)
+    implementation(monitoring.opentelemetry.logback)
 
     // database
     implementation(database.mongodb)
@@ -164,6 +171,8 @@ dependencies {
 
     // dev
     devImplementation(dev.keycloak.adminClient)
+    devImplementation(monitoring.opentelemetry.sdk)
+    devImplementation(monitoring.opentelemetry.exporter.otlp)
 
     moduleImplementation(projects.integrations.api)
     // depend on all integrations by default

infra/monitoring/.env

@@ -0,0 +1 @@
+COMPOSE_PROJECT_NAME=snoty