opentelemetry-js/packages/opentelemetry-core/README.md

OpenTelemetry Core

This package provides default implementations of the OpenTelemetry API for trace and metrics. It's intended for use both on the server and in the browser.

Built-in Implementations

• OpenTelemetry Core
  • Built-in Implementations
    • Built-in Propagators
      • HttpTraceContext Propagator
      • B3 Propagator
      • Composite Propagator
      • Correlation Context Propagator
    • Built-in Sampler
      • Always Sampler
      • Never Sampler
      • Probability Sampler
  • Useful links
  • License

Built-in Propagators

HttpTraceContext Propagator

OpenTelemetry provides a text-based approach to propagate context to remote services using the W3C Trace Context HTTP headers.

This is used as a default Propagator

const api = require("@opentelemetry/api");
const { HttpTraceContext } = require("@opentelemetry/core");

/* Set Global Propagator */
api.propagation.setGlobalPropagator(new HttpTraceContext());

B3 Propagator

This is propagator for the B3 HTTP header format, which sends a SpanContext on the wire in an HTTP request, allowing other services to create spans with the right context. Based on: https://github.com/openzipkin/b3-propagation

const api = require("@opentelemetry/api");
const { B3Propagator } = require("@opentelemetry/core");

/* Set Global Propagator */
api.propagation.setGlobalPropagator(new B3Propagator());

Composite Propagator

Combines multiple propagators into a single propagator.

const api = require("@opentelemetry/api");
const { CompositePropagator } = require("@opentelemetry/core");

/* Set Global Propagator */
api.propagation.setGlobalPropagator(new CompositePropagator());

Correlation Context Propagator

Provides a text-based approach to propagate correlation context to remote services using the OpenTelemetry CorrelationContext Propagation HTTP headers.

const api = require("@opentelemetry/api");
const { HttpCorrelationContext } = require("@opentelemetry/core");

/* Set Global Propagator */
api.propagation.setGlobalPropagator(new HttpCorrelationContext());

Built-in Sampler

Sampler is used to make decisions on Span sampling.

Always Sampler

Samples every trace regardless of upstream sampling decisions.

This is used as a default Sampler

const { NodeTracerProvider } = require("@opentelemetry/node");
const { ALWAYS_SAMPLER } = require("@opentelemetry/core");

const tracerProvider = new NodeTracerProvider({
  sampler: ALWAYS_SAMPLER
});

Never Sampler

Doesn't sample any trace, regardless of upstream sampling decisions.

const { NodeTracerProvider } = require("@opentelemetry/node");
const { NEVER_SAMPLER } = require("@opentelemetry/core");

const tracerProvider = new NodeTracerProvider({
  sampler: NEVER_SAMPLER
});

Probability Sampler

Samples a configurable percentage of traces, and additionally samples any trace that was sampled upstream.

const { NodeTracerProvider } = require("@opentelemetry/node");
const { ProbabilitySampler } = require("@opentelemetry/core");

const tracerProvider = new NodeTracerProvider({
  sampler: new ProbabilitySampler(0.5)
});

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 on gitter

License

Apache 2.0 - See LICENSE for more information.