feat(node-sdk): add support for multiple metric readers (#5777)

Co-authored-by: Marc Pichler <marc.pichler@dynatrace.com>

experimental/CHANGELOG.md

@@ -16,8 +16,23 @@ For notes on migrating to 2.x / 0.200.x see [the upgrade guide](doc/upgrade-to-2
 
 ### :rocket: Features
 
-*feat(opentelemetry-configuration): creation of basic ConfigProvider [#5809](https://github.com/open-telemetry/opentelemetry-js/pull/5809) @maryliag
-*feat(opentelemetry-configuration): creation of basic FileConfigProvider [#5863](https://github.com/open-telemetry/opentelemetry-js/pull/5863) @maryliag
+* feat(opentelemetry-configuration): creation of basic ConfigProvider [#5809](https://github.com/open-telemetry/opentelemetry-js/pull/5809) @maryliag
+* feat(opentelemetry-configuration): creation of basic FileConfigProvider [#5863](https://github.com/open-telemetry/opentelemetry-js/pull/5863) @maryliag
+* feat(sdk-node): Add support for multiple metric readers via the new `metricReaders` option in NodeSDK configuration. Users can now register multiple metric readers (e.g., Console, Prometheus) directly through the NodeSDK constructor. The old `metricReader` (singular) option is now deprecated and will show a warning if used, but remains supported for backward compatibility. Comprehensive tests and documentation have been added. [#5760](https://github.com/open-telemetry/opentelemetry-js/issues/5760)
+  * **Migration:**
+    - Before:
+
+      ```js
+      const sdk = new NodeSDK({ metricReader: myMetricReader });
+      ```
+
+    - After:
+
+      ```js
+      const sdk = new NodeSDK({ metricReaders: [myMetricReader] });
+      ```
+
+  * Users should migrate to the new `metricReaders` array option for future compatibility. The old option will be removed in an upcoming experimental version.
 
 ### :bug: Bug Fixes
 
@@ -138,7 +153,7 @@ For notes on migrating to 2.x / 0.200.x see [the upgrade guide](doc/upgrade-to-2
 
 ### :house: (Internal)
 
-* chore(instrumentation-grpc): remove unused findIndex() function [#5372](https://github.com/open-telemetry/opentelemetry-js/pull/5372) @cjihrig
+* refactor(instrumentation-grpc): remove unused findIndex() function [#5372](https://github.com/open-telemetry/opentelemetry-js/pull/5372) @cjihrig
 * refactor(otlp-exporter-base): remove unnecessary isNaN() checks [#5374](https://github.com/open-telemetry/opentelemetry-js/pull/5374) @cjihrig
 * refactor(exporter-prometheus): remove unnecessary isNaN() check [#5377](https://github.com/open-telemetry/opentelemetry-js/pull/5377) @cjihrig
 * refactor(sdk-node): move code to auto-instantiate propagators into utils [#5355](https://github.com/open-telemetry/opentelemetry-js/pull/5355) @pichlermarc

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

@@ -85,9 +85,9 @@ import {
 
 export type MeterProviderConfig = {
   /**
-   * Reference to the MetricReader instance by the NodeSDK
+   * Reference to the MetricReader instances by the NodeSDK
    */
-  reader?: IMetricReader;
+  readers?: IMetricReader[];
   /**
    * List of {@link ViewOptions}s that should be passed to the MeterProvider
    */
@@ -312,10 +312,20 @@ export class NodeSDK {
       this.configureLoggerProviderFromEnv();
     }
 
-    if (configuration.metricReader || configuration.views) {
+    if (
+      configuration.metricReaders ||
+      configuration.metricReader ||
+      configuration.views
+    ) {
       const meterProviderConfig: MeterProviderConfig = {};
-      if (configuration.metricReader) {
-        meterProviderConfig.reader = configuration.metricReader;
+
+      if (configuration.metricReaders) {
+        meterProviderConfig.readers = configuration.metricReaders;
+      } else if (configuration.metricReader) {
+        meterProviderConfig.readers = [configuration.metricReader];
+        diag.warn(
+          "The 'metricReader' option is deprecated. Please use 'metricReaders' instead."
+        );
       }
 
       if (configuration.views) {
@@ -395,8 +405,8 @@ export class NodeSDK {
       configureMetricProviderFromEnv();
     if (this._meterProviderConfig || metricReadersFromEnv.length > 0) {
       const readers: IMetricReader[] = [];
-      if (this._meterProviderConfig?.reader) {
-        readers.push(this._meterProviderConfig.reader);
+      if (this._meterProviderConfig?.readers) {
+        readers.push(...this._meterProviderConfig.readers);
       }
 
       if (readers.length === 0) {

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

@@ -35,7 +35,9 @@ export interface NodeSDKConfiguration {
   /** @deprecated use logRecordProcessors instead*/
   logRecordProcessor: LogRecordProcessor;
   logRecordProcessors?: LogRecordProcessor[];
+  /** @deprecated use metricReaders instead*/
   metricReader: IMetricReader;
+  metricReaders?: IMetricReader[];
   views: ViewOptions[];
   instrumentations: (Instrumentation | Instrumentation[])[];
   resource: Resource;

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

@@ -322,6 +322,123 @@ describe('Node SDK', () => {
       delete env.OTEL_TRACES_EXPORTER;
     });
 
+    it('should register a meter provider if multiple readers are provided', async () => {
+      // need to set OTEL_TRACES_EXPORTER to none since default value is otlp
+      // which sets up an exporter and affects the context manager
+      env.OTEL_TRACES_EXPORTER = 'none';
+      const consoleExporter = new ConsoleMetricExporter();
+      const inMemoryExporter = new InMemoryMetricExporter(
+        AggregationTemporality.CUMULATIVE
+      );
+      const metricReader1 = new PeriodicExportingMetricReader({
+        exporter: consoleExporter,
+        exportIntervalMillis: 100,
+        exportTimeoutMillis: 100,
+      });
+      const metricReader2 = new PeriodicExportingMetricReader({
+        exporter: inMemoryExporter,
+        exportIntervalMillis: 100,
+        exportTimeoutMillis: 100,
+      });
+
+      const sdk = new NodeSDK({
+        metricReaders: [metricReader1, metricReader2],
+        autoDetectResources: false,
+      });
+
+      sdk.start();
+
+      assert.strictEqual(
+        context['_getContextManager'](),
+        ctxManager,
+        'context manager should not change'
+      );
+      assert.strictEqual(
+        propagation['_getGlobalPropagator'](),
+        propagator,
+        'propagator should not change'
+      );
+      assert.strictEqual(
+        (trace.getTracerProvider() as ProxyTracerProvider).getDelegate(),
+        delegate,
+        'tracer provider should not have changed'
+      );
+
+      const meterProvider = metrics.getMeterProvider() as MeterProvider;
+      assert.ok(meterProvider instanceof MeterProvider);
+
+      // Verify that both metric readers are registered
+      const sharedState = (meterProvider as any)['_sharedState'];
+      assert.strictEqual(sharedState.metricCollectors.length, 2);
+
+      await sdk.shutdown();
+      delete env.OTEL_TRACES_EXPORTER;
+    });
+
+    it('should show deprecation warning when using metricReader option', async () => {
+      // need to set OTEL_TRACES_EXPORTER to none since default value is otlp
+      // which sets up an exporter and affects the context manager
+      env.OTEL_TRACES_EXPORTER = 'none';
+      const exporter = new ConsoleMetricExporter();
+      const metricReader = new PeriodicExportingMetricReader({
+        exporter: exporter,
+        exportIntervalMillis: 100,
+        exportTimeoutMillis: 100,
+      });
+
+      const warnSpy = Sinon.spy(diag, 'warn');
+
+      const sdk = new NodeSDK({
+        metricReader: metricReader,
+        autoDetectResources: false,
+      });
+
+      sdk.start();
+
+      // Verify deprecation warning was shown
+      Sinon.assert.calledWith(
+        warnSpy,
+        "The 'metricReader' option is deprecated. Please use 'metricReaders' instead."
+      );
+
+      assert.ok(metrics.getMeterProvider() instanceof MeterProvider);
+
+      await sdk.shutdown();
+      delete env.OTEL_TRACES_EXPORTER;
+    });
+
+    it('should not show deprecation warning when using metricReaders option', async () => {
+      // need to set OTEL_TRACES_EXPORTER to none since default value is otlp
+      // which sets up an exporter and affects the context manager
+      env.OTEL_TRACES_EXPORTER = 'none';
+      const exporter = new ConsoleMetricExporter();
+      const metricReader = new PeriodicExportingMetricReader({
+        exporter: exporter,
+        exportIntervalMillis: 100,
+        exportTimeoutMillis: 100,
+      });
+
+      const warnSpy = Sinon.spy(diag, 'warn');
+
+      const sdk = new NodeSDK({
+        metricReaders: [metricReader],
+        autoDetectResources: false,
+      });
+
+      sdk.start();
+
+      // Verify no metricReader deprecation warning was shown
+      Sinon.assert.neverCalledWith(
+        warnSpy,
+        "The 'metricReader' option is deprecated. Please use 'metricReaders' instead."
+      );
+
+      assert.ok(metrics.getMeterProvider() instanceof MeterProvider);
+
+      await sdk.shutdown();
+      delete env.OTEL_TRACES_EXPORTER;
+    });
+
     it('should register a logger provider if a log record processor is provided', async () => {
       env.OTEL_TRACES_EXPORTER = 'none';
       const logRecordExporter = new InMemoryLogRecordExporter();
@@ -617,7 +734,7 @@ describe('Node SDK', () => {
       // Local functions to test if a mocked method is ever called with a specific argument or regex matching for an argument.
       // Needed because of race condition with parallel detectors.
       const callArgsContains = (
-        mockedFunction: sinon.SinonSpy,
+        mockedFunction: Sinon.SinonSpy,
         arg: any
       ): boolean => {
         return mockedFunction.getCalls().some(call => {
@@ -625,7 +742,7 @@ describe('Node SDK', () => {
         });
       };
       const callArgsMatches = (
-        mockedFunction: sinon.SinonSpy,
+        mockedFunction: Sinon.SinonSpy,
         regex: RegExp
       ): boolean => {
         return mockedFunction.getCalls().some(call => {