feat: add OTLP metrics sample

Signed-off-by: David Ashpole <[email protected]>

samples/otlpmetricexport/.prettierrc.js

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+// Copyright 2025 Google LLC
+//
+// 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.
+
+module.exports = {
+  ...require('gts/.prettierrc.json')
+}

samples/otlpmetricexport/README.md

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+# Overview
+
+This example shows how to send metrics to an OTLP *(OpenTelemetry Protocol)* endpoint that is protected by GCP authentication. The sample showcases the metric export using gRPC
+
+## Installation
+
+```sh
+# from root of repo, build all packages
+npm install
+```
+
+## Run the Application
+
+```sh
+# export necessary OTEL environment variables
+export OTEL_RESOURCE_ATTRIBUTES="gcp.project_id=<project-id>"
+export OTEL_EXPORTER_OTLP_ENDPOINT=<endpoint>
+
+# run the app - this starts app at port 8080
+# the start script uses gRPC to export
+cd samples/otlpmetricexport && npm run start
+```
+
+## View metrics
+
+https://console.cloud.google.com//monitoring/metrics-explorer?project=your-project-id
+
+1. Select the Metric from the dropdown. You should see it under the resource "Generic Task":
+
+   <img width="1584" alt="choose metric type" src="images/choose-metric-type.png?raw=true"/>
+
+2. View the timeseries:
+
+   <img width="1584" alt="view timeseries" src="images/metric-timeseries.png?raw=true"/>
+
+
+## Useful links
+- For more information on OpenTelemetry, visit: <https://opentelemetry.io/>
+- For more information on metrics, visit: <https://opentelemetry.io/docs/concepts/signals/metrics/>
+
+## LICENSE
+
+Apache License 2.0

samples/otlpmetricexport/package.json

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+{
+  "name": "otlp-metrics-export",
+  "version": "0.1.0",
+  "private": true,
+  "author": "Google Inc.",
+  "license": "Apache-2.0",
+  "scripts": {
+    "start": "ts-node ./src/index.ts",
+    "lint": "gts lint",
+    "clean": "gts clean",
+    "fix": "gts fix",
+    "compile": "tsc",
+    "test": "",
+    "pretest": "npm run compile"
+  },
+  "keywords": [],
+  "dependencies": {
+    "@opentelemetry/api": "1.9.0",
+    "@opentelemetry/auto-instrumentations-node": "0.50.0",
+    "@opentelemetry/exporter-metrics-otlp-grpc": "0.53.0",
+    "@opentelemetry/resources": "1.26.0",
+    "@opentelemetry/sdk-node": "0.53.0",
+    "@opentelemetry/sdk-metrics": "1.26.0",
+    "@grpc/grpc-js": "1.11.3",
+    "express": "4.21.0",
+    "google-auth-library": "9.14.1",
+    "axios": "1.7.7"
+  },
+  "devDependencies": {
+    "gts": "5.3.1",
+    "typescript": "4.9.5",
+    "ts-node": "10.9.2"
+  },
+  "description": "This example shows how to send metrics to an OTLP *(OpenTelemetry Protocol)* endpoint that is protected by GCP authentication over gRPC."
+}

samples/otlpmetricexport/src/index.ts

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+// Copyright 2025 Google LLC
+//
+// 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 * as opentelemetry from '@opentelemetry/sdk-node';
+import { AuthClient, GoogleAuth } from 'google-auth-library';
+import { credentials } from '@grpc/grpc-js';
+import {
+  getResourceDetectors as getResourceDetectorsFromEnv,
+} from '@opentelemetry/auto-instrumentations-node';
+import {
+  metrics,
+  diag,
+  DiagConsoleLogger,
+} from '@opentelemetry/api';
+import { OTLPMetricExporter } from '@opentelemetry/exporter-metrics-otlp-grpc';
+import { PeriodicExportingMetricReader } from '@opentelemetry/sdk-metrics';
+
+async function getAuthenticatedClient(): Promise<AuthClient> {
+  const auth: GoogleAuth = new GoogleAuth({
+    scopes: 'https://www.googleapis.com/auth/cloud-platform',
+  });
+  return await auth.getClient();
+}
+
+diag.setLogger(
+  new DiagConsoleLogger(),
+  opentelemetry.core.getEnv().OTEL_LOG_LEVEL
+);
+
+
+// Express App that exports traces via gRPC with protobuf
+async function main() {
+  const authenticatedClient: AuthClient = await getAuthenticatedClient();
+
+  const sdk = new opentelemetry.NodeSDK({
+    metricReader: new PeriodicExportingMetricReader({
+      // Export metrics every 10 seconds. 5 seconds is the smallest sample period allowed by
+      // Cloud Monitoring.
+      exportIntervalMillis: 10_000,
+      exporter: new OTLPMetricExporter({
+        credentials: credentials.combineChannelCredentials(
+          credentials.createSsl(),
+          credentials.createFromGoogleCredential(authenticatedClient)
+        ),
+      }),
+    }),
+    resourceDetectors: getResourceDetectorsFromEnv(),
+  });
+  sdk.start();
+
+  // Create a meter
+  const meter = metrics.getMeterProvider().getMeter("metrics-sample");
+
+  // Create a counter instrument
+  const counter = meter.createCounter("metric_name");
+  // Record a measurement
+  counter.add(10, { key: "value" });
+
+  // Wait for the metric to be exported
+  await new Promise((resolve) => {
+    setTimeout(resolve, 11_000);
+  });
+
+  // Gracefully shut down the SDK to flush telemetry when the program exits
+  process.on('SIGTERM', () => {
+    sdk
+      .shutdown()
+      .then(() => diag.debug('OpenTelemetry SDK terminated'))
+      .catch(error => diag.error('Error terminating OpenTelemetry SDK', error));
+  });
+}
+
+main();

samples/otlpmetricexport/tsconfig.json

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+{
+  "extends": "gts/tsconfig-google.json",
+  "compilerOptions": {
+    "rootDir": ".",
+    "outDir": "build",
+    "esModuleInterop": true
+  },
+  "include": [
+    "src/**/*.ts",
+    "test/**/*.ts"
+  ]
+}