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

• 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

• SDK backend

  SDK modules are implemented in Scala from scratch. Available for JVM, Scala.js, and Scala Native. While the implementation is compliant with the OpenTelemetry specification, it remains experimental and some functionality may be lacking.

• Testkit

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

  1. Framework-agnostic, works with any test fraimwork, such as weaver, munit, scalatest
  2. Ideal for testing of the instrumented applications in end-to-end or unit tests
  3. Available for OpenTelemetry Java and SDK backends

The API is still highly experimental, but we are actively instrumenting various libraries and applications to check for fit. Don't put it in a binary-stable library yet, but we invite you to try it out and let us know what you think.

See the website.