fix(sdk-node): Allow Defining Sampler with Exporter in Env

experimental/CHANGELOG.md

@@ -15,6 +15,7 @@ All notable changes to experimental packages in this project will be documented
 
 ### :bug: (Bug Fix)
 
+* fix(sdk-node): allow using samplers when the exporter is defined in the environment [#4394](https://github.com/open-telemetry/opentelemetry-js/pull/4394) @JacksonWeber
 * fix(instrumentation): use caret range on import-in-the-middle [#4380](https://github.com/open-telemetry/opentelemetry-js/pull/4380) @pichlermarc
 * fix(instrumentation): do not import 'path' in browser runtimes [#4378](https://github.com/open-telemetry/opentelemetry-js/pull/4378) @pichlermarc
   * Fixes a bug where bundling for web would fail due to `InstrumentationNodeModuleDefinition` importing `path`

experimental/packages/opentelemetry-sdk-node/src/sdk.ts

@@ -101,6 +101,11 @@ export class NodeSDK {
   public constructor(configuration: Partial<NodeSDKConfiguration> = {}) {
     const env = getEnv();
     const envWithoutDefaults = getEnvWithoutDefaults();
+    const envExporterWithConfiguration =
+      env.OTEL_TRACES_EXPORTER &&
+      (configuration.sampler ||
+        configuration.spanLimits ||
+        configuration.idGenerator);
 
     if (env.OTEL_SDK_DISABLED) {
       this._disabled = true;
@@ -126,7 +131,12 @@ export class NodeSDK {
 
     this._autoDetectResources = configuration.autoDetectResources ?? true;
 
-    if (configuration.spanProcessor || configuration.traceExporter) {
+    // If there are configuration options to read, we need to create a new TracerProvider even if the exporter is configured in the environment
+    if (
+      configuration.traceExporter ||
+      configuration.spanProcessor ||
+      envExporterWithConfiguration
+    ) {
       const tracerProviderConfig: NodeTracerConfig = {};
 
       if (configuration.sampler) {

experimental/packages/opentelemetry-sdk-node/test/sdk.test.ts

@@ -176,6 +176,29 @@ describe('Node SDK', () => {
       assert.ok(apiTracerProvider.getDelegate() instanceof NodeTracerProvider);
     });
 
+    it('should register a tracer provider if an exporter is provided via env', async () => {
+      env.OTEL_TRACES_EXPORTER = 'console';
+      const sdk = new NodeSDK({
+        autoDetectResources: false,
+      });
+
+      sdk.start();
+
+      assert.ok(!(metrics.getMeterProvider() instanceof MeterProvider));
+
+      assert.ok(
+        context['_getContextManager']().constructor.name ===
+          DefaultContextManager.name
+      );
+      assert.ok(
+        propagation['_getGlobalPropagator']() instanceof CompositePropagator
+      );
+      const apiTracerProvider =
+        trace.getTracerProvider() as ProxyTracerProvider;
+      assert.ok(apiTracerProvider.getDelegate() instanceof NodeTracerProvider);
+      delete env.OTEL_TRACES_EXPORTER;
+    });
+
     it('should register a tracer provider if a span processor is provided', async () => {
       const exporter = new ConsoleSpanExporter();
       const spanProcessor = new SimpleSpanProcessor(exporter);