feat: implement child span count

packages/opentelemetry-exporter-collector/src/transform.ts

@@ -197,7 +197,7 @@ export function toCollectorSpan(span: ReadableSpan): collectorTypes.Span {
     status: span.status,
     sameProcessAsParentSpan: !!span.parentSpanId,
     links: toCollectorLinks(span),
-    // childSpanCount: // not implemented
+    childSpanCount: span.numberOfChildren,
   };
 }
 

packages/opentelemetry-exporter-collector/src/types.ts

@@ -371,12 +371,12 @@ export interface Span {
    */
   sameProcessAsParentSpan?: boolean;
 
-  //@TODO - do we use it in opentelemetry or it is not needed?
-  // /**
-  //  * An optional number of child spans that were generated while this span was
-  //  * active. If set, allows an implementation to detect missing child spans.
-  //  */
-  // childSpanCount?: number;
+  /**
+   * An optional number of child spans that were generated while this span was
+   * active. If set, allows an implementation to detect missing child spans.
+   */
+  childSpanCount?: number;
+
   /**
    * The included links.
    */

packages/opentelemetry-exporter-collector/test/helper.ts

@@ -67,6 +67,7 @@ export const mockedReadableSpan: ReadableSpan = {
     },
   ],
   duration: [0, 8885000],
+  numberOfChildren: 1,
 };
 
 export function ensureSpanIsCorrect(span: collectorTypes.Span) {
@@ -79,6 +80,7 @@ export function ensureSpanIsCorrect(span: collectorTypes.Span) {
     kind: 0,
     startTime: '2019-11-18T23:36:05.429803070Z',
     endTime: '2019-11-18T23:36:05.438688070Z',
+    childSpanCount: 1,
     attributes: {
       droppedAttributesCount: 0,
       attributeMap: {

packages/opentelemetry-exporter-jaeger/test/jaeger.test.ts

@@ -124,6 +124,7 @@ describe('JaegerExporter', () => {
         links: [],
         events: [],
         duration: [32, 800000000],
+        numberOfChildren: 0,
       };
 
       exporter.export([readableSpan], (result: ExportResult) => {

packages/opentelemetry-exporter-jaeger/test/transform.test.ts

@@ -66,6 +66,7 @@ describe('transform', () => {
           },
         ],
         duration: [32, 800000000],
+        numberOfChildren: 0,
       };
 
       const thriftSpan = spanToThrift(readableSpan);
@@ -139,6 +140,7 @@ describe('transform', () => {
         links: [],
         events: [],
         duration: [32, 800000000],
+        numberOfChildren: 0,
       };
 
       const thriftSpan = spanToThrift(readableSpan);
@@ -202,6 +204,7 @@ describe('transform', () => {
         ],
         events: [],
         duration: [32, 800000000],
+        numberOfChildren: 0,
       };
 
       const thriftSpan = spanToThrift(readableSpan);

packages/opentelemetry-exporter-zipkin/test/zipkin.test.ts

@@ -45,6 +45,7 @@ function getReadableSpan() {
     attributes: {},
     links: [],
     events: [],
+    numberOfChildren: 0,
   };
   return readableSpan;
 }
@@ -157,6 +158,7 @@ describe('ZipkinExporter', () => {
             attributes: { key3: 'value3' },
           },
         ],
+        numberOfChildren: 0,
       };
       const span2: ReadableSpan = {
         name: 'my-span',
@@ -174,6 +176,7 @@ describe('ZipkinExporter', () => {
         attributes: {},
         links: [],
         events: [],
+        numberOfChildren: 0,
       };
 
       const exporter = new ZipkinExporter({

packages/opentelemetry-tracing/src/BasicTracer.ts

@@ -184,6 +184,7 @@ export class BasicTracer implements types.Tracer {
     }
 
     if (typeof (parent as types.Span).context === 'function') {
+      (parent as Span).addChild();
       return (parent as Span).context();
     }
     return undefined;

packages/opentelemetry-tracing/src/Span.ts

@@ -44,6 +44,7 @@ export class Span implements types.Span, ReadableSpan {
     code: types.CanonicalCode.OK,
   };
   endTime: types.HrTime = [0, 0];
+  numberOfChildren: number = 0;
   private _ended = false;
   private _duration: types.HrTime = [-1, -1];
   private readonly _logger: types.Logger;
@@ -180,6 +181,11 @@ export class Span implements types.Span, ReadableSpan {
     return this._duration;
   }
 
+  addChild(): void {
+    if (this._ended) return;
+    this.numberOfChildren++;
+  }
+
   private _isSpanEnded(): boolean {
     if (this._ended) {
       this._logger.warn(

packages/opentelemetry-tracing/src/export/ReadableSpan.ts

@@ -36,4 +36,5 @@ export interface ReadableSpan {
   readonly links: Link[];
   readonly events: TimedEvent[];
   readonly duration: HrTime;
+  readonly numberOfChildren: number;
 }

packages/opentelemetry-tracing/test/BasicTracer.test.ts

@@ -211,6 +211,33 @@ describe('BasicTracer', () => {
       childSpan.end();
     });
 
+    it('should record the child count spans', () => {
+      const tracer = new BasicTracer();
+      const span = tracer.startSpan('my-span');
+      const childSpan = tracer.startSpan('child-span', {
+        parent: span,
+      });
+      assert.strictEqual((span as Span).numberOfChildren, 1);
+      const grandChildSpan = tracer.startSpan('grand-child-span', {
+        parent: span,
+      });
+      assert.strictEqual((span as Span).numberOfChildren, 2);
+      grandChildSpan.end();
+      span.end();
+      childSpan.end();
+    });
+
+    it('should not record the child span count when span is ended', () => {
+      const tracer = new BasicTracer();
+      const span = tracer.startSpan('my-span');
+      span.end();
+      const childSpan = tracer.startSpan('child-span', {
+        parent: span,
+      });
+      childSpan.end();
+      assert.strictEqual((span as Span).numberOfChildren, 0);
+    });
+
     it('should start a span with name and with invalid parent span', () => {
       const tracer = new BasicTracer();
       const span = tracer.startSpan('my-span', {