lightstep-tracer/src/imp/propagator_b3.js

> ❗ **This instrumentation is no longer recommended**. Please review [documentation on setting up and configuring the OpenTelemetry Node.js Launcher](https://github.com/lightstep/otel-launcher-node) or [OpenTelemetry JS (Browser)](https://github.com/open-

import LightStepPropagator from './propagator_ls';

const CARRIER_B3_TRACER_STATE_PREFIX = 'x-b3-';

export default class B3Propagator extends LightStepPropagator {
    constructor(tracer) {
        super(tracer);
        this._carrierPrefix = CARRIER_B3_TRACER_STATE_PREFIX;
    }

    inject(spanContext, carrier) {
        if (!carrier) {
            this._tracer._error('Unexpected null carrier in call to inject');
            return;
        }
        if (typeof carrier !== 'object') {
            this._tracer._error(`Unexpected '${typeof carrier}' FORMAT_TEXT_MAP carrier in call to inject`);
            return;
        }

        let traceId = spanContext.traceGUID();
        if (traceId.length === 32 && traceId.substr(0, 16) === '0000000000000000') {
            traceId = traceId.substr(16); // take least significant 8 bytes (16 chars)
        }

        carrier[`${this._carrierPrefix}spanid`] = spanContext._guid;
        carrier[`${this._carrierPrefix}traceid`] = traceId;
        if (spanContext._sampled) {
            carrier[`${this._carrierPrefix}sampled`] = '1';
        } else {
            carrier[`${this._carrierPrefix}sampled`] = '0';
        }
        spanContext.forEachBaggageItem((key, value) => {
            carrier[`${this._baggagePrefix}${key}`] = value;
        });
        return carrier;
    }
}