feat: change the default sampler to be always on

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        container: ['node:14.0.0']
+        container: ['node:16.0.0']
         node_api_target: ['18.0.0']
         include:
           - container: 'node:16.0.0'
@@ -42,7 +42,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        container: ['node:14.0.0']
+        container: ['node:16.0.0']
         node_api_target: ['18.0.0']
         include:
           - container: 'node:16.0.0'

src/tracing/options.ts

@@ -15,6 +15,7 @@
  */
 import * as util from 'util';
 import {
+  AlwaysOnSampler,
   ConsoleSpanExporter,
   SpanExporter,
   SpanProcessor,
@@ -49,6 +50,18 @@ import type {
   StartTracingOptions,
   TracingOptions,
 } from './types';
+import { NodeTracerConfig } from '@opentelemetry/sdk-trace-node';
+
+function defaultSampler(config: NodeTracerConfig) {
+  if (
+    config.sampler === undefined &&
+    getNonEmptyEnvVar('OTEL_TRACES_SAMPLER') === undefined
+  ) {
+    return new AlwaysOnSampler();
+  }
+
+  return undefined;
+}
 
 export function _setDefaultOptions(
   options: StartTracingOptions = {}
@@ -88,8 +101,11 @@ export function _setDefaultOptions(
   );
 
   const extraTracerConfig = options.tracerConfig || {};
+
+  const sampler = defaultSampler(extraTracerConfig);
   const tracerConfig = {
     resource,
+    sampler,
     ...extraTracerConfig,
   };
 

src/types.ts

@@ -41,6 +41,7 @@ export type EnvVarKey =
   | 'OTEL_SERVICE_NAME'
   | 'OTEL_SPAN_LINK_COUNT_LIMIT'
   | 'OTEL_TRACES_EXPORTER'
+  | 'OTEL_TRACES_SAMPLER'
   | 'SPLUNK_ACCESS_TOKEN'
   | 'SPLUNK_AUTOINSTRUMENT_PACKAGE_NAMES'
   | 'SPLUNK_AUTOMATIC_LOG_COLLECTION'

test/options.test.ts

@@ -37,6 +37,7 @@ import {
   SimpleSpanProcessor,
   SpanExporter,
   InMemorySpanExporter,
+  AlwaysOffSampler,
 } from '@opentelemetry/sdk-trace-base';
 
 import { strict as assert } from 'assert';
@@ -212,6 +213,7 @@ describe('options', () => {
       instrumentations: [testInstrumentation],
       tracerConfig: {
         resource: new Resource({ attr1: 'value1' }),
+        sampler: new AlwaysOffSampler(),
         idGenerator: idGenerator,
       },
       resourceFactory,
@@ -230,6 +232,7 @@ describe('options', () => {
       instrumentations: [testInstrumentation],
       tracerConfig: {
         resource: new Resource({ attr1: 'value1' }),
+        sampler: new AlwaysOffSampler(),
         idGenerator: idGenerator,
       },
       spanExporterFactory: testSpanExporterFactory,

test/tracing/default_setup.test.ts

@@ -14,11 +14,14 @@
  * limitations under the License.
  */
 
+import { strict as assert } from 'assert';
 import { test } from 'node:test';
 import { assertTracingPipeline, setupMocks } from './common';
 
 import { parseOptionsAndConfigureInstrumentations } from '../../src/instrumentations';
 import { startTracing, stopTracing } from '../../src/tracing';
+import { trace } from '@opentelemetry/api';
+import { AlwaysOnSampler } from '@opentelemetry/sdk-trace-base';
 
 test('Tracing: set up with defaults', async () => {
   const mocks = setupMocks();
@@ -29,5 +32,9 @@ test('Tracing: set up with defaults', async () => {
     'http://localhost:4318/v1/traces',
     '@splunk/otel'
   );
+
+  const provider = trace.getTracerProvider();
+  assert(provider.getTracer('test')['_sampler'] instanceof AlwaysOnSampler);
+
   await stopTracing();
 });

test/tracing/env_options.test.ts

@@ -14,11 +14,14 @@
  * limitations under the License.
  */
 
+import { strict as assert } from 'assert';
 import { test } from 'node:test';
 import { assertTracingPipeline, setupMocks } from './common';
 
 import { parseOptionsAndConfigureInstrumentations } from '../../src/instrumentations';
 import { startTracing, stopTracing } from '../../src/tracing';
+import { trace } from '@opentelemetry/api';
+import { ParentBasedSampler } from '@opentelemetry/sdk-trace-base';
 
 test('Tracing: set up with env options', async () => {
   const mocks = setupMocks();
@@ -30,9 +33,14 @@ test('Tracing: set up with env options', async () => {
   process.env.OTEL_EXPORTER_OTLP_ENDPOINT = url;
   process.env.OTEL_SERVICE_NAME = serviceName;
   process.env.SPLUNK_ACCESS_TOKEN = accessToken;
+  process.env.OTEL_TRACES_SAMPLER = 'parentbased_always_on';
 
   const { tracingOptions } = parseOptionsAndConfigureInstrumentations();
   startTracing(tracingOptions);
   assertTracingPipeline(mocks, `${url}/v1/traces`, serviceName, accessToken);
+
+  const provider = trace.getTracerProvider();
+  assert(provider.getTracer('test')['_sampler'] instanceof ParentBasedSampler);
+
   await stopTracing();
 });