Add file operation telemetry (#1068)

Introduces telemetry for file create, read, and update operations.

This change adds the `gemini_cli.file.operation.count` metric, recorded by the `read-file`, `read-many-files`, and `write-file` tools.

The metric includes the following attributes:
    - `operation` (string: `create`, `read`, `update`): The type of file operation.
    - `lines` (optional, Int): Number of lines in the file.
    - `mimetype` (optional, string): Mimetype of the file.
    - `extension` (optional, string): File extension of the file.

Here is a stacked bar chart of file operations by extension (`js`, `ts`, `md`):
![image](https://github.com/user-attachments/assets/3e8f8ea9-6155-4186-863c-075cc47647c5)

Here is a stacked bar chart of file operations by type (`create`, `read`, `update`):
![image](https://github.com/user-attachments/assets/3fcf491d-31d0-4ba8-80e6-7fd2bd9c7c27)

#750 

cc @allenhutchison as discussed 

7 files changed, 265 insertions, 36 deletions

diff --git a/packages/core/src/telemetry/constants.ts b/packages/core/src/telemetry/constants.ts
index bbcdbada..de760205 100644
--- a/packages/core/src/telemetry/constants.ts
+++ b/packages/core/src/telemetry/constants.ts
@@ -19,3 +19,4 @@ export const METRIC_API_REQUEST_COUNT = 'gemini_cli.api.request.count';
 export const METRIC_API_REQUEST_LATENCY = 'gemini_cli.api.request.latency';
 export const METRIC_TOKEN_USAGE = 'gemini_cli.token.usage';
 export const METRIC_SESSION_COUNT = 'gemini_cli.session.count';
+export const METRIC_FILE_OPERATION_COUNT = 'gemini_cli.file.operation.count';
diff --git a/packages/core/src/telemetry/metrics.test.ts b/packages/core/src/telemetry/metrics.test.ts
index 7e24b9ad..4fcdd9e1 100644
--- a/packages/core/src/telemetry/metrics.test.ts
+++ b/packages/core/src/telemetry/metrics.test.ts
@@ -5,32 +5,84 @@
  */
 
 import { describe, it, expect, vi, beforeEach, type Mock } from 'vitest';
-import { Counter, Meter, metrics } from '@opentelemetry/api';
-import { initializeMetrics, recordTokenUsageMetrics } from './metrics.js';
+import type {
+  Counter,
+  Meter,
+  Attributes,
+  Context,
+  Histogram,
+} from '@opentelemetry/api';
 import { Config } from '../config/config.js';
+import { FileOperation } from './metrics.js';
 
-const mockCounter = {
-  add: vi.fn(),
+const mockCounterAddFn: Mock<
+  (value: number, attributes?: Attributes, context?: Context) => void
+> = vi.fn();
+const mockHistogramRecordFn: Mock<
+  (value: number, attributes?: Attributes, context?: Context) => void
+> = vi.fn();
+
+const mockCreateCounterFn: Mock<(name: string, options?: unknown) => Counter> =
+  vi.fn();
+const mockCreateHistogramFn: Mock<
+  (name: string, options?: unknown) => Histogram
+> = vi.fn();
+
+const mockCounterInstance = {
+  add: mockCounterAddFn,
 } as unknown as Counter;
 
-const mockMeter = {
-  createCounter: vi.fn().mockReturnValue(mockCounter),
-  createHistogram: vi.fn().mockReturnValue({ record: vi.fn() }),
+const mockHistogramInstance = {
+  record: mockHistogramRecordFn,
+} as unknown as Histogram;
+
+const mockMeterInstance = {
+  createCounter: mockCreateCounterFn.mockReturnValue(mockCounterInstance),
+  createHistogram: mockCreateHistogramFn.mockReturnValue(mockHistogramInstance),
 } as unknown as Meter;
 
-vi.mock('@opentelemetry/api', () => ({
-  metrics: {
-    getMeter: vi.fn(),
-  },
-  ValueType: {
-    INT: 1,
-  },
-}));
+function originalOtelMockFactory() {
+  return {
+    metrics: {
+      getMeter: vi.fn(),
+    },
+    ValueType: {
+      INT: 1,
+    },
+  };
+}
+
+vi.mock('@opentelemetry/api', originalOtelMockFactory);
 
 describe('Telemetry Metrics', () => {
-  beforeEach(() => {
-    vi.clearAllMocks();
-    (metrics.getMeter as Mock).mockReturnValue(mockMeter);
+  let initializeMetricsModule: typeof import('./metrics.js').initializeMetrics;
+  let recordTokenUsageMetricsModule: typeof import('./metrics.js').recordTokenUsageMetrics;
+  let recordFileOperationMetricModule: typeof import('./metrics.js').recordFileOperationMetric;
+
+  beforeEach(async () => {
+    vi.resetModules();
+    vi.doMock('@opentelemetry/api', () => {
+      const actualApi = originalOtelMockFactory();
+      (actualApi.metrics.getMeter as Mock).mockReturnValue(mockMeterInstance);
+      return actualApi;
+    });
+
+    const metricsJsModule = await import('./metrics.js');
+    initializeMetricsModule = metricsJsModule.initializeMetrics;
+    recordTokenUsageMetricsModule = metricsJsModule.recordTokenUsageMetrics;
+    recordFileOperationMetricModule = metricsJsModule.recordFileOperationMetric;
+
+    const otelApiModule = await import('@opentelemetry/api');
+
+    mockCounterAddFn.mockClear();
+    mockCreateCounterFn.mockClear();
+    mockCreateHistogramFn.mockClear();
+    mockHistogramRecordFn.mockClear();
+    (otelApiModule.metrics.getMeter as Mock).mockClear();
+
+    (otelApiModule.metrics.getMeter as Mock).mockReturnValue(mockMeterInstance);
+    mockCreateCounterFn.mockReturnValue(mockCounterInstance);
+    mockCreateHistogramFn.mockReturnValue(mockHistogramInstance);
   });
 
   describe('recordTokenUsageMetrics', () => {
@@ -39,14 +91,18 @@ describe('Telemetry Metrics', () => {
     } as unknown as Config;
 
     it('should not record metrics if not initialized', () => {
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 100, 'input');
-      expect(mockCounter.add).not.toHaveBeenCalled();
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 100, 'input');
+      expect(mockCounterAddFn).not.toHaveBeenCalled();
     });
 
     it('should record token usage with the correct attributes', () => {
-      initializeMetrics(mockConfig);
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 100, 'input');
-      expect(mockCounter.add).toHaveBeenCalledWith(100, {
+      initializeMetricsModule(mockConfig);
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 100, 'input');
+      expect(mockCounterAddFn).toHaveBeenCalledTimes(2);
+      expect(mockCounterAddFn).toHaveBeenNthCalledWith(1, 1, {
+        'session.id': 'test-session-id',
+      });
+      expect(mockCounterAddFn).toHaveBeenNthCalledWith(2, 100, {
         'session.id': 'test-session-id',
         model: 'gemini-pro',
         type: 'input',
@@ -54,30 +110,32 @@ describe('Telemetry Metrics', () => {
     });
 
     it('should record token usage for different types', () => {
-      initializeMetrics(mockConfig);
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 50, 'output');
-      expect(mockCounter.add).toHaveBeenCalledWith(50, {
+      initializeMetricsModule(mockConfig);
+      mockCounterAddFn.mockClear();
+
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 50, 'output');
+      expect(mockCounterAddFn).toHaveBeenCalledWith(50, {
         'session.id': 'test-session-id',
         model: 'gemini-pro',
         type: 'output',
       });
 
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 25, 'thought');
-      expect(mockCounter.add).toHaveBeenCalledWith(25, {
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 25, 'thought');
+      expect(mockCounterAddFn).toHaveBeenCalledWith(25, {
         'session.id': 'test-session-id',
         model: 'gemini-pro',
         type: 'thought',
       });
 
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 75, 'cache');
-      expect(mockCounter.add).toHaveBeenCalledWith(75, {
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 75, 'cache');
+      expect(mockCounterAddFn).toHaveBeenCalledWith(75, {
         'session.id': 'test-session-id',
         model: 'gemini-pro',
         type: 'cache',
       });
 
-      recordTokenUsageMetrics(mockConfig, 'gemini-pro', 125, 'tool');
-      expect(mockCounter.add).toHaveBeenCalledWith(125, {
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-pro', 125, 'tool');
+      expect(mockCounterAddFn).toHaveBeenCalledWith(125, {
         'session.id': 'test-session-id',
         model: 'gemini-pro',
         type: 'tool',
@@ -85,13 +143,83 @@ describe('Telemetry Metrics', () => {
     });
 
     it('should handle different models', () => {
-      initializeMetrics(mockConfig);
-      recordTokenUsageMetrics(mockConfig, 'gemini-ultra', 200, 'input');
-      expect(mockCounter.add).toHaveBeenCalledWith(200, {
+      initializeMetricsModule(mockConfig);
+      mockCounterAddFn.mockClear();
+
+      recordTokenUsageMetricsModule(mockConfig, 'gemini-ultra', 200, 'input');
+      expect(mockCounterAddFn).toHaveBeenCalledWith(200, {
         'session.id': 'test-session-id',
         model: 'gemini-ultra',
         type: 'input',
       });
     });
   });
+
+  describe('recordFileOperationMetric', () => {
+    const mockConfig = {
+      getSessionId: () => 'test-session-id',
+    } as unknown as Config;
+
+    it('should not record metrics if not initialized', () => {
+      recordFileOperationMetricModule(
+        mockConfig,
+        FileOperation.CREATE,
+        10,
+        'text/plain',
+        'txt',
+      );
+      expect(mockCounterAddFn).not.toHaveBeenCalled();
+    });
+
+    it('should record file creation with all attributes', () => {
+      initializeMetricsModule(mockConfig);
+      recordFileOperationMetricModule(
+        mockConfig,
+        FileOperation.CREATE,
+        10,
+        'text/plain',
+        'txt',
+      );
+
+      expect(mockCounterAddFn).toHaveBeenCalledTimes(2);
+      expect(mockCounterAddFn).toHaveBeenNthCalledWith(1, 1, {
+        'session.id': 'test-session-id',
+      });
+      expect(mockCounterAddFn).toHaveBeenNthCalledWith(2, 1, {
+        'session.id': 'test-session-id',
+        operation: FileOperation.CREATE,
+        lines: 10,
+        mimetype: 'text/plain',
+        extension: 'txt',
+      });
+    });
+
+    it('should record file read with minimal attributes', () => {
+      initializeMetricsModule(mockConfig);
+      mockCounterAddFn.mockClear();
+
+      recordFileOperationMetricModule(mockConfig, FileOperation.READ);
+      expect(mockCounterAddFn).toHaveBeenCalledWith(1, {
+        'session.id': 'test-session-id',
+        operation: FileOperation.READ,
+      });
+    });
+
+    it('should record file update with some attributes', () => {
+      initializeMetricsModule(mockConfig);
+      mockCounterAddFn.mockClear();
+
+      recordFileOperationMetricModule(
+        mockConfig,
+        FileOperation.UPDATE,
+        undefined,
+        'application/javascript',
+      );
+      expect(mockCounterAddFn).toHaveBeenCalledWith(1, {
+        'session.id': 'test-session-id',
+        operation: FileOperation.UPDATE,
+        mimetype: 'application/javascript',
+      });
+    });
+  });
 });
diff --git a/packages/core/src/telemetry/metrics.ts b/packages/core/src/telemetry/metrics.ts
index 59979ef3..124bc602 100644
--- a/packages/core/src/telemetry/metrics.ts
+++ b/packages/core/src/telemetry/metrics.ts
@@ -20,15 +20,23 @@ import {
   METRIC_API_REQUEST_LATENCY,
   METRIC_TOKEN_USAGE,
   METRIC_SESSION_COUNT,
+  METRIC_FILE_OPERATION_COUNT,
 } from './constants.js';
 import { Config } from '../config/config.js';
 
+export enum FileOperation {
+  CREATE = 'create',
+  READ = 'read',
+  UPDATE = 'update',
+}
+
 let cliMeter: Meter | undefined;
 let toolCallCounter: Counter | undefined;
 let toolCallLatencyHistogram: Histogram | undefined;
 let apiRequestCounter: Counter | undefined;
 let apiRequestLatencyHistogram: Histogram | undefined;
 let tokenUsageCounter: Counter | undefined;
+let fileOperationCounter: Counter | undefined;
 let isMetricsInitialized = false;
 
 function getCommonAttributes(config: Config): Attributes {
@@ -75,7 +83,10 @@ export function initializeMetrics(config: Config): void {
     description: 'Counts the total number of tokens used.',
     valueType: ValueType.INT,
   });
-
+  fileOperationCounter = meter.createCounter(METRIC_FILE_OPERATION_COUNT, {
+    description: 'Counts file operations (create, read, update).',
+    valueType: ValueType.INT,
+  });
   const sessionCounter = meter.createCounter(METRIC_SESSION_COUNT, {
     description: 'Count of CLI sessions started.',
     valueType: ValueType.INT,
@@ -171,3 +182,21 @@ export function recordApiErrorMetrics(
     model,
   });
 }
+
+export function recordFileOperationMetric(
+  config: Config,
+  operation: FileOperation,
+  lines?: number,
+  mimetype?: string,
+  extension?: string,
+): void {
+  if (!fileOperationCounter || !isMetricsInitialized) return;
+  const attributes: Attributes = {
+    ...getCommonAttributes(config),
+    operation,
+  };
+  if (lines !== undefined) attributes.lines = lines;
+  if (mimetype !== undefined) attributes.mimetype = mimetype;
+  if (extension !== undefined) attributes.extension = extension;
+  fileOperationCounter.add(1, attributes);
+}
diff --git a/packages/core/src/tools/read-file.ts b/packages/core/src/tools/read-file.ts
index 586a7123..5cf49209 100644
--- a/packages/core/src/tools/read-file.ts
+++ b/packages/core/src/tools/read-file.ts
@@ -10,6 +10,11 @@ import { makeRelative, shortenPath } from '../utils/paths.js';
 import { BaseTool, ToolResult } from './tools.js';
 import { isWithinRoot, processSingleFileContent } from '../utils/fileUtils.js';
 import { Config } from '../config/config.js';
+import { getSpecificMimeType } from '../utils/fileUtils.js';
+import {
+  recordFileOperationMetric,
+  FileOperation,
+} from '../telemetry/metrics.js';
 
 /**
  * Parameters for the ReadFile tool
@@ -145,6 +150,19 @@ export class ReadFileTool extends BaseTool<ReadFileToolParams, ToolResult> {
       };
     }
 
+    const lines =
+      typeof result.llmContent === 'string'
+        ? result.llmContent.split('\n').length
+        : undefined;
+    const mimetype = getSpecificMimeType(params.absolute_path);
+    recordFileOperationMetric(
+      this.config,
+      FileOperation.READ,
+      lines,
+      mimetype,
+      path.extname(params.absolute_path),
+    );
+
     return {
       llmContent: result.llmContent,
       returnDisplay: result.returnDisplay,
diff --git a/packages/core/src/tools/read-many-files.ts b/packages/core/src/tools/read-many-files.ts
index 107e16b3..62430c10 100644
--- a/packages/core/src/tools/read-many-files.ts
+++ b/packages/core/src/tools/read-many-files.ts
@@ -14,9 +14,14 @@ import {
   detectFileType,
   processSingleFileContent,
   DEFAULT_ENCODING,
+  getSpecificMimeType,
 } from '../utils/fileUtils.js';
 import { PartListUnion } from '@google/genai';
 import { Config } from '../config/config.js';
+import {
+  recordFileOperationMetric,
+  FileOperation,
+} from '../telemetry/metrics.js';
 
 /**
  * Parameters for the ReadManyFilesTool.
@@ -420,6 +425,18 @@ Use this tool when the user's query implies needing the content of several files
           contentParts.push(fileReadResult.llmContent); // This is a Part for image/pdf
         }
         processedFilesRelativePaths.push(relativePathForDisplay);
+        const lines =
+          typeof fileReadResult.llmContent === 'string'
+            ? fileReadResult.llmContent.split('\n').length
+            : undefined;
+        const mimetype = getSpecificMimeType(filePath);
+        recordFileOperationMetric(
+          this.config,
+          FileOperation.READ,
+          lines,
+          mimetype,
+          path.extname(filePath),
+        );
       }
     }
 
diff --git a/packages/core/src/tools/write-file.ts b/packages/core/src/tools/write-file.ts
index b9e07034..b19b00ac 100644
--- a/packages/core/src/tools/write-file.ts
+++ b/packages/core/src/tools/write-file.ts
@@ -26,6 +26,11 @@ import {
 import { GeminiClient } from '../core/client.js';
 import { DEFAULT_DIFF_OPTIONS } from './diffOptions.js';
 import { ModifiableTool, ModifyContext } from './modifiable-tool.js';
+import { getSpecificMimeType } from '../utils/fileUtils.js';
+import {
+  recordFileOperationMetric,
+  FileOperation,
+} from '../telemetry/metrics.js';
 
 /**
  * Parameters for the WriteFile tool
@@ -271,6 +276,27 @@ export class WriteFileTool
 
       const displayResult: FileDiff = { fileDiff, fileName };
 
+      const lines = fileContent.split('\n').length;
+      const mimetype = getSpecificMimeType(params.file_path);
+      const extension = path.extname(params.file_path); // Get extension
+      if (isNewFile) {
+        recordFileOperationMetric(
+          this.config,
+          FileOperation.CREATE,
+          lines,
+          mimetype,
+          extension,
+        );
+      } else {
+        recordFileOperationMetric(
+          this.config,
+          FileOperation.UPDATE,
+          lines,
+          mimetype,
+          extension,
+        );
+      }
+
       return {
         llmContent: llmSuccessMessage,
         returnDisplay: displayResult,
diff --git a/packages/core/src/utils/fileUtils.ts b/packages/core/src/utils/fileUtils.ts
index d726c053..cb4d333a 100644
--- a/packages/core/src/utils/fileUtils.ts
+++ b/packages/core/src/utils/fileUtils.ts
@@ -17,6 +17,16 @@ const MAX_LINE_LENGTH_TEXT_FILE = 2000;
 export const DEFAULT_ENCODING: BufferEncoding = 'utf-8';
 
 /**
+ * Looks up the specific MIME type for a file path.
+ * @param filePath Path to the file.
+ * @returns The specific MIME type string (e.g., 'text/python', 'application/javascript') or undefined if not found or ambiguous.
+ */
+export function getSpecificMimeType(filePath: string): string | undefined {
+  const lookedUpMime = mime.lookup(filePath);
+  return typeof lookedUpMime === 'string' ? lookedUpMime : undefined;
+}
+
+/**
  * Checks if a path is within a given root directory.
  * @param pathToCheck The absolute path to check.
  * @param rootDirectory The absolute root directory.