otel-json-exporter

A tiny Kotlin Multiplatform (Android + iOS) helper for sending OTLP/JSON telemetry.

Published as io.github.codedtx:json_exporter (library) and io.github.codedtx.jsonexporter (Gradle plugin).

Most OpenTelemetry HTTP exporters (opentelemetry-java, opentelemetry-swift) speak protobuf only. When your collector/gateway accepts application/json instead, you still need to send the bytes and, on iOS, fix the trace/span id encoding. This library owns exactly that shared step — the POST and the id normalisation — so it isn't duplicated in Kotlin and Swift.

It has no OpenTelemetry SDK dependency — only Ktor, kotlinx.serialization, and coroutines. Each platform keeps its own serialize step (it consumes SDK-specific span/log/metric types); this library takes the resulting OTLP/JSON string and delivers it.

package jsonexporter

object OtlpJsonTransport {
    /** POST [body] as application/json to [endpoint]. Blocking, never throws. Returns true on 2xx. */
    fun send(endpoint: String, headers: Map<String, String>, body: String): Boolean
}

/** Rewrite base64 traceId/spanId/parentSpanId in [json] to the lowercase hex OTLP/JSON requires. */
fun fixOtlpJsonIds(json: String): String

• send blocks and never throws — call it from a background/export worker thread, not the main thread.
• fixOtlpJsonIds is needed when your serializer emits proto3-canonical JSON (base64 byte fields), e.g. swift-protobuf. It's a safe no-op on already-hex ids.

Both options resolve from Maven Central (mavenCentral() is usually already in your repos).

The plugin adds the library to commonMain for you.

settings.gradle.kts — the plugin resolves from pluginManagement, and the library it adds resolves from dependencyResolutionManagement, so both need mavenCentral():

pluginManagement {
    repositories {
        google()
        gradlePluginPortal()
        mavenCentral()
    }
}

dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
    }
}

Module build.gradle.kts (KMP):

plugins {
    id("io.github.codedtx.jsonexporter") version "1.1.1"
}

settings.gradle.kts:

dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
    }
}

Module build.gradle.kts (KMP):

kotlin {
    sourceSets {
        commonMain.dependencies {
            implementation("io.github.codedtx:json_exporter:1.1.1")
        }
    }
}

import jsonexporter.OtlpJsonTransport
import jsonexporter.fixOtlpJsonIds

// 1. Serialize your spans/logs/metrics to an OTLP/JSON string with your platform SDK.
val json = fixOtlpJsonIds(serializedOtlpJson)   // no-op on Android/hex; fixes base64 on iOS

// 2. Send it.
val ok = OtlpJsonTransport.send(
    endpoint = "https://your-gateway/api/v1/telemetry/traces",
    headers = emptyMap(),
    body = json,
)

Apache License 2.0 — see LICENSE.