132 lines
4.0 KiB
Markdown
132 lines
4.0 KiB
Markdown
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# OpenTelemetry Propagator B3
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[![NPM Published Version][npm-img]][npm-url]
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[![Apache License][license-image]][license-image]
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The OpenTelemetry b3 propagator package provides multiple propagator
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implementations for systems using the b3 context format. See the
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[b3 specification][b3-spec] for complete details.
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## B3 Formats
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Single-Header Format:
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```bash
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b3: {TraceId}-{SpanId}-{SamplingState}-{ParentSpanId}
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```
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Multi-Header Format:
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```bash
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X-B3-TraceId: {TraceId}
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X-B3-SpanId: {SpanId}
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X-B3-ParentSpanId: {ParentSpanId}
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X-B3-Sampled: {SamplingState}
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```
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- {TraceId}
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- Required
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- Encoded as 32 or 16 lower-hex characters
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- 16 character traceIds will be converted to 32 characters by left-padding
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with 0s to conform with the [OpenTelemetry specification][otel-spec-id-format]
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- {SpanId}
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- Required
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- Encoded as 16 lower-hex characters
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- {ParentSpanId}
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- Optional
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- Used to support the Zipkin functionality where the client and server spans
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that make up an HTTP request share the same id
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- Not propagated by this library
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- {SamplingState} - Single-header
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- Optional
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- Valid values
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- 1 - Accept
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- 0 - Deny
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- d - Debug
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- Absent - Defer sampling decision
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- {SamplingState} - Multi-header
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- Optional
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- Valid values
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- 1 - Accept
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- 0 - Deny
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- {Flags} - Multi-header
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- Optional
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- 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.
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## B3 Propagation
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The default `B3Propagator` implements b3 propagation according to the
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[OpenTelemetry specification][otel-b3-requirements]. It extracts b3 context
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from multi and single header encodings and injects context using the
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single-header b3 encoding by default. The inject encoding can be changed to
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multi-header via configuration. See the examples below.
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### B3 Single-Header Configuration
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```javascript
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const api = require('@opentelemetry/api');
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const { B3Propagator } = require('@opentelemetry/propagator-b3');
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api.propagation.setGlobalPropagator(new B3Propagator());
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```
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### B3 Multi-Header Configuration
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```javascript
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const api = require('@opentelemetry/api');
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const { B3Propagator, B3InjectEncoding } = require('@opentelemetry/propagator-b3');
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api.propagation.setGlobalPropagator(
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new B3Propagator({ injectEncoding: B3InjectEncoding.MULTI_HEADER })
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);
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```
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### B3 Single and Multi-Header Configuration
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The B3Propagator always extracts both the single and multi-header b3 encodings.
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If you need to inject both encodings this can accomplished using a composite
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propagator.
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```javascript
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const api = require('@opentelemetry/api');
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const { CompositePropagator } = require('@opentelemetry/core');
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const { B3Propagator, B3InjectEncoding } = require('@opentelemetry/propagator-b3');
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api.propagation.setGlobalPropagator(
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new CompositePropagator({
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propagators: [
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new B3Propagator(),
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new B3Propagator({ injectEncoding: B3InjectEncoding.MULTI_HEADER }),
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],
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})
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);
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```
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## Useful links
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- For more information on OpenTelemetry, visit: <https://opentelemetry.io/>
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- For more about OpenTelemetry JavaScript: <https://github.com/open-telemetry/opentelemetry-js>
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- For help or feedback on this project, join us in [GitHub Discussions][discussions-url]
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## License
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Apache 2.0 - See [LICENSE][license-url] for more information.
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[discussions-url]: https://github.com/open-telemetry/opentelemetry-js/discussions
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[license-url]: https://github.com/open-telemetry/opentelemetry-js-contrib/blob/master/LICENSE
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[license-image]: https://img.shields.io/badge/license-Apache_2.0-green.svg?style=flat
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[npm-url]: https://www.npmjs.com/package/@opentelemetry/propagator-b3
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[npm-img]: https://badge.fury.io/js/%40opentelemetry%2Fpropagator-b3.svg
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[b3-spec]: https://github.com/openzipkin/b3-propagation
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[otel-b3-requirements]: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/context/api-propagators.md#b3-requirements
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[otel-spec-id-format]: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/api.md#retrieving-the-traceid-and-spanid
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