Respect sampled bit in probability sampler

packages/opentelemetry-core/src/index.ts

@@ -29,5 +29,6 @@ export * from './trace/NoRecordingSpan';
 export * from './trace/sampler/ProbabilitySampler';
 export * from './trace/spancontext-utils';
 export * from './trace/TraceState';
+export * from './utils/trace-flags';
 export * from './utils/url';
 export * from './utils/wrap';

packages/opentelemetry-core/src/trace/sampler/ProbabilitySampler.ts

@@ -15,6 +15,7 @@
  */
 
 import { Sampler, SpanContext } from '@opentelemetry/api';
+import { isSampled } from '../../utils/trace-flags';
 
 /** Sampler that samples a given fraction of traces. */
 export class ProbabilitySampler implements Sampler {
@@ -23,6 +24,8 @@ export class ProbabilitySampler implements Sampler {
   }
 
   shouldSample(parentContext?: SpanContext) {
+    if (parentContext && parentContext.traceFlags !== undefined)
+      return isSampled(parentContext.traceFlags);
     if (this._probability >= 1.0) return true;
     else if (this._probability <= 0) return false;
     return Math.random() < this._probability;

packages/opentelemetry-core/src/utils/trace-flags.ts

@@ -0,0 +1,26 @@
+/*!
+ * Copyright 2020, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { TraceFlags } from '@opentelemetry/api';
+
+/**
+ * Given a bitmask, determine if the SAMPLED flag is set
+ *
+ * @param traceFlags 8 bit mask of tracing flags
+ */
+export function isSampled(traceFlags: TraceFlags = TraceFlags.UNSAMPLED) {
+  return (TraceFlags.SAMPLED & traceFlags) === TraceFlags.SAMPLED;
+}

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

@@ -14,13 +14,12 @@
  * limitations under the License.
  */
 
-import { TraceFlags } from '@opentelemetry/api';
 import { unrefTimer } from '@opentelemetry/core';
-import { SpanProcessor } from '../SpanProcessor';
-import { SpanExporter } from './SpanExporter';
 import { Span } from '../Span';
-import { ReadableSpan } from './ReadableSpan';
+import { SpanProcessor } from '../SpanProcessor';
 import { BufferConfig } from '../types';
+import { ReadableSpan } from './ReadableSpan';
+import { SpanExporter } from './SpanExporter';
 
 const DEFAULT_BUFFER_SIZE = 100;
 const DEFAULT_BUFFER_TIMEOUT_MS = 20_000;
@@ -56,7 +55,6 @@ export class BatchSpanProcessor implements SpanProcessor {
   onStart(span: Span): void {}
 
   onEnd(span: Span): void {
-    if (span.context().traceFlags !== TraceFlags.SAMPLED) return;
     this._addToBuffer(span.toReadableSpan());
   }
 

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

@@ -14,10 +14,9 @@
  * limitations under the License.
  */
 
-import { TraceFlags } from '@opentelemetry/api';
+import { Span } from '../Span';
 import { SpanProcessor } from '../SpanProcessor';
 import { SpanExporter } from './SpanExporter';
-import { Span } from '../Span';
 
 /**
  * An implementation of the {@link SpanProcessor} that converts the {@link Span}
@@ -32,7 +31,6 @@ export class SimpleSpanProcessor implements SpanProcessor {
   onStart(span: Span): void {}
 
   onEnd(span: Span): void {
-    if (span.context().traceFlags !== TraceFlags.SAMPLED) return;
     this._exporter.export([span.toReadableSpan()], () => {});
   }
 

packages/opentelemetry-tracing/test/export/BatchSpanProcessor.test.ts

@@ -14,15 +14,15 @@
  * limitations under the License.
  */
 
+import { ALWAYS_SAMPLER } from '@opentelemetry/core';
 import * as assert from 'assert';
 import * as sinon from 'sinon';
 import {
-  Span,
   BasicTracerProvider,
-  InMemorySpanExporter,
   BatchSpanProcessor,
+  InMemorySpanExporter,
+  Span,
 } from '../../src';
-import { NEVER_SAMPLER, ALWAYS_SAMPLER, NoopLogger } from '@opentelemetry/core';
 
 function createSampledSpan(spanName: string): Span {
   const tracer = new BasicTracerProvider({
@@ -33,16 +33,6 @@ function createSampledSpan(spanName: string): Span {
   return span as Span;
 }
 
-function createUnSampledSpan(spanName: string): Span {
-  const tracer = new BasicTracerProvider({
-    sampler: NEVER_SAMPLER,
-    logger: new NoopLogger(),
-  }).getTracer('default');
-  const span = tracer.startSpan(spanName, { isRecording: false });
-  span.end();
-  return span as Span;
-}
-
 describe('BatchSpanProcessor', () => {
   const name = 'span-name';
   const defaultBufferConfig = {
@@ -97,16 +87,6 @@ describe('BatchSpanProcessor', () => {
       assert.strictEqual(exporter.getFinishedSpans().length, 0);
     });
 
-    it('should not export the unsampled spans', () => {
-      const processor = new BatchSpanProcessor(exporter, defaultBufferConfig);
-      for (let i = 0; i < defaultBufferConfig.bufferSize * 2; i++) {
-        const span = createUnSampledSpan(`${name}_${i}`);
-        processor.onEnd(span);
-        assert.strictEqual(exporter.getFinishedSpans().length, 0);
-      }
-      processor.shutdown();
-    });
-
     it('should force flush when timeout exceeded', done => {
       const clock = sinon.useFakeTimers();
       const processor = new BatchSpanProcessor(exporter, defaultBufferConfig);