feat: add debug logging to resource auto-detection

Signed-off-by: Adam Egyed <[email protected]>

packages/opentelemetry-resources/src/platform/node/config.ts

@@ -0,0 +1,23 @@
+/*
+ * Copyright The 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.
+ */
+
+/**
+ * ResourceDetectionConfig provides an interface for configuring resource auto-detection.
+ */
+export interface ResourceDetectionConfig {
+  /** Optional Logger. */
+  logger?: (message: string) => void;
+}

packages/opentelemetry-resources/src/platform/node/detect-resources.ts

@@ -17,14 +17,20 @@
 import { Resource } from '../../Resource';
 import { envDetector, awsEc2Detector, gcpDetector } from './detectors';
 import { Detector } from '../../types';
+import { ResourceDetectionConfig } from './config';
+import * as util from 'util';
 
 const DETECTORS: Array<Detector> = [envDetector, awsEc2Detector, gcpDetector];
 
 /**
  * Runs all resource detectors and returns the results merged into a single
  * Resource.
+ *
+ * @param config Configuration object for resource detection
  */
-export const detectResources = async (): Promise<Resource> => {
+export const detectResources = async (
+  config: ResourceDetectionConfig = {}
+): Promise<Resource> => {
   const resources: Array<Resource> = await Promise.all(
     DETECTORS.map(d => {
       try {
@@ -34,6 +40,24 @@ export const detectResources = async (): Promise<Resource> => {
       }
     })
   );
+  if (config.logger) {
+    resources.forEach((resource, index) => {
+      // Only print populated resources
+      if (Object.keys(resource.labels).length > 0) {
+        const resourceDebugString = util.inspect(resource.labels, {
+          depth: 2,
+          breakLength: Infinity,
+          sorted: true,
+          compact: false,
+        });
+        const detectorName = DETECTORS[index].constructor
+          ? DETECTORS[index].constructor.name
+          : 'Unknown detector';
+        config.logger!(`${detectorName} found resource.`);
+        config.logger!(resourceDebugString);
+      }
+    });
+  }
   return resources.reduce(
     (acc, resource) => acc.merge(resource),
     Resource.createTelemetrySDKResource()

packages/opentelemetry-resources/test/detect-resources.test.ts

@@ -16,6 +16,7 @@
 
 import * as nock from 'nock';
 import * as sinon from 'sinon';
+import * as assert from 'assert';
 import { URL } from 'url';
 import { Resource, detectResources } from '../src';
 import { awsEc2Detector } from '../src/platform/node/detectors';
@@ -162,4 +163,19 @@ describe('detectResources', async () => {
       stub.restore();
     });
   });
+
+  describe('with a debug logger', () => {
+    it('prints detected resources to the logger', async () => {
+      // This test depends on the env detector to be functioning as intended
+      const mockedLogger = sinon.fake();
+      await detectResources({ logger: mockedLogger });
+
+      assert.deepStrictEqual(mockedLogger.getCall(0).args, [
+        'EnvDetector found resource.',
+      ]);
+      assert.deepStrictEqual(mockedLogger.getCall(1).args, [
+        "{\n  'service.instance.id': '627cc493',\n  'service.name': 'my-service',\n  'service.namespace': 'default',\n  'service.version': '0.0.1'\n}",
+      ]);
+    });
+  });
 });