OpenTelemetry Composite Sampling

Note: This is an experimental package under active development. New releases may include breaking changes.

This package provides implementations of composite samplers that propagate sampling information across a trace. These samplers provide the implementation for (the experimental) Consistent Probability Sampling specification.

Quick Start

To get started you will need to install a compatible OpenTelemetry SDK.

Samplers

This module exports samplers that follow the general behavior of the standard SDK samplers, but ensuring it is consistent across a trace by using the tracestate header. Notably, the tracestate can be examined in exported spans to reconstruct population metrics.

import {
  createCompositeSampler,
  createComposableAlwaysOffSampler,
  createComposableAlwaysOnSampler,
  createComposableParentThresholdSampler,
  createComposableProbabilitySampler,
  createComposableRuleBasedSampler
} from '@opentelemetry/sampler-composite';

// never sample
const sampler = createCompositeSampler(createComposableAlwaysOffSampler());
// always sample
const sampler = createCompositeSampler(createComposableAlwaysOnSampler());
// follow the parent, or otherwise sample with a probability if root
const sampler = createCompositeSampler(
    createComposableParentThresholdSampler(createComposableProbabilitySampler(0.3)));

// An example of a rule-based sampler implementing the example at
// https://opentelemetry.io/docs/specs/otel/trace/sdk/#composablerulebased
const isHealthCheck = (_ctx, _traceId, _name, _kind, attrs, _links) => {
  return attrs['http.route'] === '/healthcheck';
};
const isCheckout = (_ctx, _traceId, _name, _kind, attrs, _links) => {
  return attrs['http.route'] === '/checkout';
};
const sampler = createCompositeSampler(
  createComposableParentThresholdSampler( // Honour sampling flag in `traceparent` header.
    // Otherwise...
    createComposableRuleBasedSampler([
      // ...never sample `/healthcheck` requests.
      [isHealthCheck, createComposableAlwaysOffSampler()],
      // ...always sample `/checkout` requests.
      [isCheckout, createComposableAlwaysOnSampler()],
      // ...sample 10% of all other requests.
      [() => true, createComposableProbabilitySampler(0.1)]
    ])
  )
);
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Useful links

• For more information on OpenTelemetry, visit: https://opentelemetry.io/
• For more about OpenTelemetry JavaScript: https://github.com/open-telemetry/opentelemetry-js
• For help or feedback on this project, join us in GitHub Discussions

License

Apache 2.0 - See LICENSE for more information.