@opentelemetry/propagator-b3

What is @opentelemetry/propagator-b3?

The @opentelemetry/propagator-b3 npm package is used for B3 propagation format which is a convention for passing trace context information across service boundaries. It supports both single-header and multi-header encoding. This package is part of the OpenTelemetry project which provides a collection of tools, APIs, and SDKs to instrument, generate, collect, and export telemetry data (metrics, logs, and traces) to help analyze a software's performance and behavior.

What are @opentelemetry/propagator-b3's main functionalities?

B3 Propagation

This feature allows the user to extract and inject B3 propagation headers. The B3Propagator can be set as the global propagator in OpenTelemetry.

const { B3Propagator } = require('@opentelemetry/propagator-b3');
const { propagation } = require('@opentelemetry/api');

// Use the B3Propagator for extracting and injecting
propagation.setGlobalPropagator(new B3Propagator());

B3 Multi-header Propagation

This feature supports the B3 multi-header propagation format, which uses multiple headers to transmit tracing information. It is useful when interacting with systems that expect B3 headers in multiple header format.

const { B3MultiPropagator } = require('@opentelemetry/propagator-b3');
const { propagation } = require('@opentelemetry/api');

// Use the B3MultiPropagator for extracting and injecting with multi-header support
propagation.setGlobalPropagator(new B3MultiPropagator());

Other packages similar to @opentelemetry/propagator-b3

jaeger-client

This package is a Node.js client for Jaeger, a distributed tracing system. It includes Jaeger Tracer which can report tracing information to a Jaeger agent or collector. Jaeger and B3 are both tracing propagation formats, but Jaeger is specific to the Jaeger tracing system, whereas B3 is a more general format used by systems like Zipkin.

zipkin

The Zipkin npm package is a library that interfaces with the Zipkin API for distributed tracing. Similar to B3, Zipkin uses B3 propagation headers for tracing across service boundaries. The Zipkin package provides more comprehensive features for interacting with Zipkin, while @opentelemetry/propagator-b3 focuses on the propagation aspect within the OpenTelemetry ecosystem.

lightstep-tracer

LightStep's tracer library for Node.js is designed to monitor the performance of distributed systems. It uses its own propagation format and is part of the LightStep ecosystem, which is a different distributed tracing solution compared to the B3 propagation used by @opentelemetry/propagator-b3.

README

OpenTelemetry Propagator B3

The OpenTelemetry b3 propagator package provides multiple propagator implementations for systems using the b3 context format. See the b3 specification for complete details.

B3 Formats

Single-Header Format:

b3: {TraceId}-{SpanId}-{SamplingState}-{ParentSpanId}

Multi-Header Format:

X-B3-TraceId: {TraceId}
X-B3-SpanId: {SpanId}
X-B3-ParentSpanId: {ParentSpanId}
X-B3-Sampled: {SamplingState}

• {TraceId}

  • Required
  • Encoded as 32 or 16 lower-hex characters
  • 16 character traceIds will be converted to 32 characters by left-padding with 0s to conform with the OpenTelemetry specification

• {SpanId}

  • Required
  • Encoded as 16 lower-hex characters

• {ParentSpanId}

  • Optional
  • Used to support the Zipkin functionality where the client and server spans that make up an HTTP request share the same id
  • Not propagated by this library

• {SamplingState} - Single-header

  • Optional
  • Valid values
    • 1 - Accept
    • 0 - Deny
    • d - Debug
    • Absent - Defer sampling decision

• {SamplingState} - Multi-header

  • Optional
  • Valid values
    • 1 - Accept
    • 0 - Deny

• {Flags} - Multi-header

  • Optional
  • Debug is encoded as X-B3-Flags: 1. Absent or any other value can be ignored. Debug implies an accept decision, so don't also send the X-B3-Sampled header.

Propagator Implementations

B3Propagator

The default B3Propagator implements b3 propagation according to the OpenTelemetry specification. It extracts b3 context from multi and single header encodings and injects context using the single-header b3 encoding. The inject encoding can be changed to multi-header via configuration.

Example usage (default):

const api = require('@opentelemetry/api');
const { B3Propagator } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(new B3Propagator());

Example usage (specify inject encoding):

const api = require('@opentelemetry/api');
const { B3Propagator } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(
  new B3Propagator({ injectEncoding: B3InjectEncoding.MULTI_HEADER })
);

B3SinglePropagator

If a distributed system only needs support for the b3 single-header encoding it can use the B3SinglePropagator directly.

Example usage:

const api = require('@opentelemetry/api');
const { B3SinglePropagator } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(new B3SinglePropagator());

B3MultiPropagator

If a distributed system only needs support for the b3 multi-header encoding it can use the B3MultiPropagator directly.

Example usage:

const api = require('@opentelemetry/api');
const { B3MultiPropagator } = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(new B3MultiPropagator());

CompositePropagator

If a distributed system needs to support both single and multiple header encodings for inject and extract the B3SinglePropagator and B3MultiPropagator can be used in conjunction with a CompositePropagator.

Example usage:

const api = require('@opentelemetry/api');
const { CompositePropagator } = require('@opentelemetry/core');
const {
  B3SinglePropagator,
  B3MultiPropagator,
} = require('@opentelemetry/propagator-b3');

api.propagation.setGlobalPropagator(
  new CompositePropagator({
    propagators: [new B3SinglePropagator(), new B3MultiPropagator()],
  })
);

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.