Modules structure

The otel4s is designed with modularity in mind. To achieve this, the project is organized into distinct high-level modules, each serving specific purposes and functionalities. These modules are: otel4s-core, otel4s-sdk, otel4s-oteljava.

The primary motivation behind this modular architecture is to keep the classpath small.

High-level modules

graph BT
  otel4s-sdk --> otel4s-core
  otel4s-oteljava --> otel4s-core

1) otel4s-core

Defines the interfaces: Tracer, Meter, and others. It also offers no-op implementations.

2) otel4s-sdk

The implementation of Open Telemetry specification written purely in Scala. Available for all platforms: JVM, Scala Native, Scala.js.

3) otel4s-oteljava

The implementation of otel4s-core interfaces. Uses OpenTelemetry Java under the hood.

High-level module structure

Each high-level module has several submodules:
1. {x}-common - the shared code, used by {x}-trace and {x}-metrics
2. {x}-trace - the tracing-specific code
3. {x}-metrics - the metrics-specific code
4. {x} - the high-level module itself - aggregates all of the above

The current structure of the modules:

graph BT
  otel4s-core --> otel4s-core-metrics
  otel4s-core --> otel4s-core-trace
  otel4s-core-metrics --> otel4s-core-common
  otel4s-core-trace --> otel4s-core-common

  otel4s-sdk --> otel4s-sdk-metrics
  otel4s-sdk --> otel4s-sdk-trace
  otel4s-sdk-metrics --> otel4s-sdk-common
  otel4s-sdk-trace --> otel4s-sdk-common

  otel4s-oteljava --> otel4s-oteljava-metrics
  otel4s-oteljava --> otel4s-oteljava-trace
  otel4s-oteljava-metrics --> otel4s-oteljava-common
  otel4s-oteljava-trace --> otel4s-oteljava-common

Which module do I need?

Let's take a look into common scenarios:

1. You develop a library, and you will use only trace-specific interfaces - use otel4s-core-trace
   
2. You develop a library, and you will use both tracing and metrics interfaces - use otel4s-core
   
3. You develop an app and want to export your telemetry - use otel4s-oteljava module