Add GCP telemetry script (#1033)

Adds a script -  `scripts/telemetry_gcp.js` - to simplify setting up a local OpenTelemetry collector that forwards data to Google Cloud. This is a follow up to the script for local telemetry `scripts/local_telemetry.js` added in #1015.

This script automates downloading necessary binaries, configuring the collector, and updating workspace settings.

Also includes `scripts/telemetry_utils.js` with shared helper functions for telemetry scripts. Will refactor `scripts/local_t elemetry.js` in next steps to use this shared functionality.

Updates `docs/core/telemetry.md` to include:
- A new "Quick Start" section
- Detailed instructions for the new GCP automated script
- Reorganization of existing sections for clarity

#750 

---
```
✨ Starting Local Telemetry Exporter for Google Cloud ✨
⚙️  Enabled telemetry in workspace settings.
🔧 Set telemetry OTLP endpoint to http://localhost:4317.
✅ Workspace settings updated.
✅ Using Google Cloud Project ID: foo-bar

🔑 Please ensure you are authenticated with Google Cloud:
  - Run `gcloud auth application-default login` OR ensure `GOOGLE_APPLICATION_CREDENTIALS` environment variable points to a valid service account key.
  - The account needs "Cloud Trace Agent", "Monitoring Metric Writer", and "Logs Writer" roles.
✅ otelcol-contrib already exists at /Users/jerop/github/gemini-cli/.gemini/otel/bin/otelcol-contrib
🧹 Cleaning up old processes and logs...
✅ Deleted old GCP collector log.
📄 Wrote OTEL collector config to /Users/jerop/github/gemini-cli/.gemini/otel/collector-gcp.yaml
🚀 Starting OTEL collector for GCP... Logs: /Users/jerop/github/gemini-cli/.gemini/otel/collector-gcp.log
⏳ Waiting for OTEL collector to start (PID: 65145)...
✅ OTEL collector started successfully on port 4317.

✨ Local OTEL collector for GCP is running.

📄 Collector logs are being written to: /Users/jerop/github/gemini-cli/.gemini/otel/collector-gcp.log

📊 View your telemetry data in Google Cloud Console:
   - Traces: https://console.cloud.google.com/traces/list?project=foo-bar
   - Metrics: https://console.cloud.google.com/monitoring/metrics-explorer?project=foo-bar
   - Logs: https://console.cloud.google.com/logs/query;query=logName%3D%22projects%2Ffoo-bar%2Flogs%2Fgemini_cli%22?project=foo-bar

Press Ctrl+C to exit.
^C
👋 Shutting down...
⚙️ Disabled telemetry in workspace settings.
🔧 Cleared telemetry OTLP endpoint.
✅ Workspace settings updated.
🛑 Stopping otelcol-contrib (PID: 65145)...
✅ otelcol-contrib stopped.
```

1 files changed, 178 insertions, 0 deletions

diff --git a/scripts/telemetry_gcp.js b/scripts/telemetry_gcp.js
new file mode 100755
index 00000000..a842625e
--- /dev/null
+++ b/scripts/telemetry_gcp.js
@@ -0,0 +1,178 @@
+#!/usr/bin/env node
+
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import path from 'path';
+import fs from 'fs';
+import { spawn, execSync } from 'child_process';
+import {
+  OTEL_DIR,
+  BIN_DIR,
+  fileExists,
+  waitForPort,
+  ensureBinary,
+  manageTelemetrySettings,
+  registerCleanup,
+} from './telemetry_utils.js';
+
+const OTEL_CONFIG_FILE = path.join(OTEL_DIR, 'collector-gcp.yaml');
+const OTEL_LOG_FILE = path.join(OTEL_DIR, 'collector-gcp.log');
+
+const getOtelConfigContent = (projectId) => `
+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: "localhost:4317"
+processors:
+  batch:
+    timeout: 1s
+exporters:
+  googlecloud:
+    project: "${projectId}"
+    metric:
+      prefix: "custom.googleapis.com/gemini_cli"
+    log:
+      default_log_name: "gemini_cli"
+  debug:
+    verbosity: detailed
+service:
+  telemetry:
+    logs:
+      level: "debug"
+    metrics:
+      level: "none"
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [googlecloud]
+    metrics:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [googlecloud, debug]
+    logs:
+      receivers: [otlp]
+      processors: [batch]
+      exporters: [googlecloud, debug]
+`;
+
+async function main() {
+  console.log('✨ Starting Local Telemetry Exporter for Google Cloud ✨');
+
+  let collectorProcess;
+  let collectorLogFd;
+
+  const originalSandboxSetting = manageTelemetrySettings(
+    true,
+    'http://localhost:4317',
+  );
+  registerCleanup(
+    () => [collectorProcess].filter((p) => p), // Function to get processes
+    () => [collectorLogFd].filter((fd) => fd), // Function to get FDs
+    originalSandboxSetting,
+  );
+
+  const projectId = process.env.GOOGLE_CLOUD_PROJECT;
+  if (!projectId) {
+    console.error(
+      '🛑 Error: GOOGLE_CLOUD_PROJECT environment variable is not set.',
+    );
+    console.log('Please set it to your Google Cloud Project ID and try again.');
+    process.exit(1);
+  }
+  console.log(`✅ Using Google Cloud Project ID: ${projectId}`);
+
+  console.log('\n🔑 Please ensure you are authenticated with Google Cloud:');
+  console.log(
+    '  - Run `gcloud auth application-default login` OR ensure `GOOGLE_APPLICATION_CREDENTIALS` environment variable points to a valid service account key.',
+  );
+  console.log(
+    '  - The account needs "Cloud Trace Agent", "Monitoring Metric Writer", and "Logs Writer" roles.',
+  );
+
+  if (!fileExists(BIN_DIR)) fs.mkdirSync(BIN_DIR, { recursive: true });
+
+  const otelcolPath = await ensureBinary(
+    'otelcol-contrib',
+    'open-telemetry/opentelemetry-collector-releases',
+    (version, platform, arch, ext) =>
+      `otelcol-contrib_${version}_${platform}_${arch}.${ext}`,
+    'otelcol-contrib',
+    false, // isJaeger = false
+  ).catch((e) => {
+    console.error(`🛑 Error getting otelcol-contrib: ${e.message}`);
+    return null;
+  });
+  if (!otelcolPath) process.exit(1);
+
+  console.log('🧹 Cleaning up old processes and logs...');
+  try {
+    execSync('pkill -f "otelcol-contrib"');
+    console.log('✅ Stopped existing otelcol-contrib process.');
+  } catch (_e) {
+    /* no-op */
+  }
+  try {
+    fs.unlinkSync(OTEL_LOG_FILE);
+    console.log('✅ Deleted old GCP collector log.');
+  } catch (e) {
+    if (e.code !== 'ENOENT') console.error(e);
+  }
+
+  if (!fileExists(OTEL_DIR)) fs.mkdirSync(OTEL_DIR, { recursive: true });
+  fs.writeFileSync(OTEL_CONFIG_FILE, getOtelConfigContent(projectId));
+  console.log(`📄 Wrote OTEL collector config to ${OTEL_CONFIG_FILE}`);
+
+  console.log(`🚀 Starting OTEL collector for GCP... Logs: ${OTEL_LOG_FILE}`);
+  collectorLogFd = fs.openSync(OTEL_LOG_FILE, 'a');
+  collectorProcess = spawn(otelcolPath, ['--config', OTEL_CONFIG_FILE], {
+    stdio: ['ignore', collectorLogFd, collectorLogFd],
+    env: { ...process.env },
+  });
+
+  console.log(
+    `⏳ Waiting for OTEL collector to start (PID: ${collectorProcess.pid})...`,
+  );
+
+  try {
+    await waitForPort(4317);
+    console.log(`✅ OTEL collector started successfully on port 4317.`);
+  } catch (err) {
+    console.error(`🛑 Error: OTEL collector failed to start on port 4317.`);
+    console.error(err.message);
+    if (collectorProcess && collectorProcess.pid) {
+      process.kill(collectorProcess.pid, 'SIGKILL');
+    }
+    if (fileExists(OTEL_LOG_FILE)) {
+      console.error('📄 OTEL Collector Log Output:');
+      console.error(fs.readFileSync(OTEL_LOG_FILE, 'utf-8'));
+    }
+    process.exit(1);
+  }
+
+  collectorProcess.on('error', (err) => {
+    console.error(`${collectorProcess.spawnargs[0]} process error:`, err);
+    process.exit(1);
+  });
+
+  console.log(`\n✨ Local OTEL collector for GCP is running.`);
+  console.log(`\n📄 Collector logs are being written to: ${OTEL_LOG_FILE}`);
+  console.log(`\n📊 View your telemetry data in Google Cloud Console:`);
+  console.log(
+    `   - Traces: https://console.cloud.google.com/traces/list?project=${projectId}`,
+  );
+  console.log(
+    `   - Metrics: https://console.cloud.google.com/monitoring/metrics-explorer?project=${projectId}`,
+  );
+  console.log(
+    `   - Logs: https://console.cloud.google.com/logs/query;query=logName%3D%22projects%2F${projectId}%2Flogs%2Fgemini_cli%22?project=${projectId}`,
+  );
+  console.log(`\nPress Ctrl+C to exit.`);
+}
+
+main();