Adds B3 propagator (#177)

* initial commit

* ckpt

* ftb

* adds options

* Update README.md

* propagate sampled flag

* add test and cleanup

Author: bg451

README.md

@@ -103,6 +103,7 @@ The OpenTracing standard JavaScript API is [documented here](https://doc.esdoc.o
 * `transport` `string` *optional*, *default=proto* - when `transport` is set to `thrift`, the Tracer will use Thrift as its transport instead of Proto over HTTP.
 * `logger` `function(level: string, message: string, payload: any): void` *optional* - specify a custom logger function. Possible `level` values are `debug`, `info`, `warn` and `error`. By default messages will be logged to the console.
 * `disable_meta_event_reporting` `bool` *optional*, *default=false* - when `disable_meta_event_reporting` is set to `true`, the tracer will disable meta event reporting even if requested by the Satellite.
+* `propagator` `dictionary` *optional*, *defaults=*`{opentracing.FORMAT_HTTP: LightStepPropagator, opentracing.FORMAT_TEXT_MAP: LightStepPropagator, opentracing.FORMAT_BINARY: UnsupportedPropagator}`: Allows inject/extract to use custom propagators for different formats. This package includes a `B3Propagator` that supports B3 headers on text maps and http headers.
 
 ### SpanImp
 

dist/lightstep-tracer.js

@@ -34,3 +34,5 @@ export const LS_META_INJECT = 'lightstep.inject_span';
 export const LS_META_SP_START = 'lightstep.span_start';
 export const LS_META_SP_FINISH = 'lightstep.span_finish';
 export const LS_META_TRACER_CREATE = 'lightstep.tracer_create';
+
+export const FORMAT_B3 = 'format.b3';

dist/lightstep-tracer.js.map

@@ -0,0 +1,14 @@
+export default class UnsupportedPropagator {
+    constructor(tracer, name) {
+        this._tracer = tracer;
+        this._name = name;
+    }
+    inject(spanContext, carrier) {
+        this._tracer._error(`Unsupported format: ${this._name}`);
+        return null;
+    }
+    extract(carrier) {
+        this._tracer._error(`Unsupported format: ${this._name}`);
+    }
+}
+

dist/lightstep-tracer.min.js

@@ -0,0 +1,33 @@
+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 '${typeof carrier}' FORMAT_TEXT_MAP carrier in call to inject`);
+            return;
+        }
+
+        carrier[`${this._carrierPrefix}spanid`] = spanContext._guid;
+        carrier[`${this._carrierPrefix}traceid`] = spanContext.traceGUID();
+        if (spanContext._sampled) {
+            carrier[`${this._carrierPrefix}sampled`] = '1';
+        } else {
+            carrier[`${this._carrierPrefix}sampled`] = '0';
+        }
+        spanContext.forEachBaggageItem((key, value) => {
+            carrier[`${this._baggagePrefix}${key}`] = value;
+        });
+        return carrier;
+    }
+}