/custom-sampler-oteljs

Primary LanguageTypeScript

Custom OpenTelemetry Sampler Demo

This project demonstrates the implementation of a custom OpenTelemetry sampler in a TypeScript Express application. The sampler combines trace ID-based sampling with deterministic attribute-based sampling decisions.

Features

  • Custom OpenTelemetry sampler implementation
  • Express.js REST API
  • TypeScript support
  • Automatic instrumentation using OpenTelemetry
  • Configurable sampling rates

Prerequisites

  • Node.js (Latest LTS version recommended)
  • npm or yarn
  • OpenTelemetry collector (for receiving traces)

Installation

  1. Clone the repository
  2. Install dependencies:
npm install

Configuration

The application uses the following key configurations:

  1. Sampling Rate: Configured in tracing.ts (currently set to 10% - 0.1)
  2. Service Name: 'sampled-service'
  3. Port: 4005

Running the Application

Run the application using npm:

npm start

API Endpoints

GET /

Returns a simple hello message and demonstrates basic span creation.

POST /api/data

Accepts JSON data and returns it with a confirmation message.

Custom Sampler Implementation

The project includes a custom sampler (DetermisticAndTraceIDSampler) that combines two sampling strategies:

  1. Trace ID-based sampling: Uses the trace ID to make consistent sampling decisions
  2. Attribute-based sampling: Allows override of sampling decisions based on span attributes

Environment Setup

Make sure to have an OpenTelemetry collector or Environment variables configured to receive traces. The application is configured to send traces using OTLP HTTP protocol.

Dependencies

Key dependencies include:

  • @opentelemetry/api
  • @opentelemetry/auto-instrumentations-node
  • @opentelemetry/sdk-trace-base
  • express
  • typescript

License

ISC

Contributing

Feel free to submit issues and pull requests.