fix: respect sampled flag in Span Processors, fix associated tests

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

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { context } from '@opentelemetry/api';
+import { context, TraceFlags } from '@opentelemetry/api';
 import {
   ExportResultCode,
   getEnv,
@@ -77,6 +77,11 @@ export abstract class BatchSpanProcessorBase<T extends BufferConfig> implements
     if (this._isShutdown) {
       return;
     }
+
+    if ((span.spanContext().traceFlags & TraceFlags.SAMPLED) === 0) {
+      return;
+    }
+
     this._addToBuffer(span);
   }
 

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

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { context } from '@opentelemetry/api';
+import { context, TraceFlags } from '@opentelemetry/api';
 import {
   ExportResultCode,
   globalErrorHandler,
@@ -50,6 +50,10 @@ export class SimpleSpanProcessor implements SpanProcessor {
       return;
     }
 
+    if ((span.spanContext().traceFlags & TraceFlags.SAMPLED) === 0) {
+      return;
+    }
+
     // prevent downstream exporter calls from generating spans
     context.with(suppressTracing(context.active()), () => {
       this._exporter.export([span], result => {

packages/opentelemetry-tracing/test/common/export/BatchSpanProcessorBase.test.ts

@@ -16,6 +16,7 @@
 
 import { diag } from '@opentelemetry/api';
 import {
+  AlwaysOffSampler,
   AlwaysOnSampler,
   ExportResultCode,
   loggingErrorHandler,
@@ -38,6 +39,15 @@ function createSampledSpan(spanName: string): Span {
   return span as Span;
 }
 
+function createUnsampledSpan(spanName: string): Span {
+  const tracer = new BasicTracerProvider({
+    sampler: new AlwaysOffSampler(),
+  }).getTracer('default');
+  const span = tracer.startSpan(spanName);
+  span.end();
+  return span as Span;
+}
+
 class BatchSpanProcessor extends BatchSpanProcessorBase<BufferConfig> {
   onInit() {}
   onShutdown() {}
@@ -141,6 +151,20 @@ describe('BatchSpanProcessorBase', () => {
       assert.strictEqual(exporter.getFinishedSpans().length, 0);
     });
 
+    it('should not export unsampled spans', async () => {
+      const processor = new BatchSpanProcessor(exporter, defaultBufferConfig);
+      const spy: sinon.SinonSpy = sinon.spy(exporter, 'export') as any;
+
+      const span = createUnsampledSpan(`${name}_0`);
+
+      processor.onEnd(span);
+
+      await processor.forceFlush();
+      assert.strictEqual(processor['_finishedSpans'].length, 0);
+      assert.strictEqual(exporter.getFinishedSpans().length, 0);
+      assert.strictEqual(spy.args.length, 0);
+    });
+
     it('should export the sampled spans with buffer size reached', done => {
       const clock = sinon.useFakeTimers();
       const processor = new BatchSpanProcessor(exporter, defaultBufferConfig);

packages/opentelemetry-tracing/test/common/export/SimpleSpanProcessor.test.ts

@@ -38,8 +38,14 @@ import { TestStackContextManager } from './TestStackContextManager';
 import { TestTracingSpanExporter } from './TestTracingSpanExporter';
 
 describe('SimpleSpanProcessor', () => {
-  const provider = new BasicTracerProvider();
-  const exporter = new InMemorySpanExporter();
+  let provider: BasicTracerProvider;
+  let exporter: InMemorySpanExporter;
+
+
+  beforeEach(() => {
+    provider = new BasicTracerProvider();
+    exporter = new InMemorySpanExporter();
+  });
 
   describe('constructor', () => {
     it('should create a SimpleSpanProcessor instance', () => {
@@ -103,7 +109,7 @@ describe('SimpleSpanProcessor', () => {
       const spanContext: SpanContext = {
         traceId: 'a3cda95b652f4a1592b449d5929fda1b',
         spanId: '5e0c63257de34c92',
-        traceFlags: TraceFlags.NONE,
+        traceFlags: TraceFlags.SAMPLED,
       };
       const span = new Span(
         provider.getTracer('default'),