otel4s

Telemetry meets higher-kinded types

otel4s is an OpenTelemetry implementation for Scala. The design goal is to fully and faithfully implement the OpenTelemetry Specification atop Cats Effect.

Features

• Simple and idiomatic metrics and tracing API

  Provides a user-friendly and idiomatic API for telemetry, designed with Typelevel ecosystem best practices. Intuitive interfaces for metrics, tracing, and context propagation.

• Minimal overhead

  The library utilizes metaprogramming techniques to reduce runtime costs and allocations. Near-zero overhead when telemetry is disabled, ensuring production performance is unaffected when tracing or metrics collection is not required.

• Modularity

  A modular architecture allows to include only the required components:

  1. Core modules: designed for library instrumentation, offering a lightweight dependency footprint
  2. Selective integration: use only the metrics or tracing functionality without requiring the other

• Cross-platform

  All modules are available for Scala 2.13 and Scala 3. Core modules are available on all platforms: JVM, Scala.js, and Scala Native.

• OpenTelemetry Java SDK backend

  The backend utilizes OpenTelemetry Java SDK under the hood, offering production-ready telemetry:

  1. Low memory overhead
  2. Extensive instrumentation ecosystem
  3. Well-tested implementation

• Pure Scala SDK

  A pure Scala SDK backend is available in the separate otel4s-sdk project for JVM, Scala.js, and Scala Native.

• Testkit

  A testkit simplifies the validation of telemetry behavior in the applications and libraries:

  1. Framework-agnostic, works with any test framework, such as weaver, munit, scalatest
  2. Ideal for testing of the instrumented applications in end-to-end or unit tests
  3. Included for the OpenTelemetry Java backend in this repo

Status

otel4s 1.0 establishes the compatibility baseline for the modules published from this repository, primarily otel4s-core*, otel4s-oteljava*, and the semantic-convention and instrumentation modules.

Artifacts that remain unstable are explicitly marked, such as *-experimental semantic-convention modules. The pure Scala SDK backend lives in the separate otel4s-sdk project.

Published modules in this repo

Module family	JVM	Scala Native	Scala.js
otel4s-core*	✅	✅	✅
otel4s-semconv*	✅	✅	✅
otel4s-instrumentation-*	✅	✅	✅
otel4s-oteljava*	✅	❌	❌

Learn more

See the website.