feat: Report coverage latency in shield metrics

packages/shield-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added metrics in the Shield coverage response to track the latency ( [#7133](https://github.com/MetaMask/core/pull/7133))
+
 ## [2.0.0]
 
 ### Changed

packages/shield-controller/src/backend.test.ts

@@ -51,6 +51,10 @@ function setup({
 }
 
 describe('ShieldRemoteBackend', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
   it('should check coverage', async () => {
     const { backend, fetchMock, getAccessToken } = setup();
 
@@ -70,14 +74,24 @@ describe('ShieldRemoteBackend', () => {
 
     const txMeta = generateMockTxMeta();
     const coverageResult = await backend.checkCoverage({ txMeta });
-    expect(coverageResult).toStrictEqual({ coverageId, ...result });
+    expect({
+      coverageId: coverageResult.coverageId,
+      message: result.message,
+      reasonCode: result.reasonCode,
+      status: result.status,
+    }).toStrictEqual({
+      coverageId,
+      ...result,
+    });
+    expect(typeof coverageResult.metrics.latency).toBe('number');
     expect(fetchMock).toHaveBeenCalledTimes(2);
     expect(getAccessToken).toHaveBeenCalledTimes(2);
   });
 
   it('should check coverage with delay', async () => {
+    const pollInterval = 100;
     const { backend, fetchMock, getAccessToken } = setup({
-      getCoverageResultPollInterval: 100,
+      getCoverageResultPollInterval: pollInterval,
     });
 
     // Mock init coverage check.
@@ -101,13 +115,38 @@ describe('ShieldRemoteBackend', () => {
     } as unknown as Response);
 
     const txMeta = generateMockTxMeta();
+
+    // generateMockTxMeta also use Date.now() to set the time, only do this after generateMockTxMeta
+    // Mock Date.now() to control latency measurement
+    // Simulate latency that includes the retry delay (poll interval + processing time)
+    let callCount = 0;
+    const startTime = 1000;
+    const expectedLatency = pollInterval + 50; // poll interval + processing time
+    const nowSpy = jest.spyOn(Date, 'now').mockImplementation(() => {
+      callCount += 1;
+      // First call: start of #getCoverageResult
+      if (callCount === 1) {
+        return startTime;
+      }
+      // Final call: end of #getCoverageResult (after retry delay)
+      return startTime + expectedLatency;
+    });
+
     const coverageResult = await backend.checkCoverage({ txMeta });
-    expect(coverageResult).toStrictEqual({
+
+    expect(coverageResult).toMatchObject({
       coverageId,
-      ...result,
+      status: result.status,
+      message: result.message,
+      reasonCode: result.reasonCode,
     });
+    expect(coverageResult.metrics.latency).toBe(expectedLatency);
+    // Latency should include the retry delay (at least the poll interval)
+    expect(coverageResult.metrics.latency).toBeGreaterThanOrEqual(pollInterval);
     expect(fetchMock).toHaveBeenCalledTimes(3);
     expect(getAccessToken).toHaveBeenCalledTimes(2);
+
+    nowSpy.mockRestore();
   });
 
   it('should throw on init coverage check failure', async () => {
@@ -187,6 +226,66 @@ describe('ShieldRemoteBackend', () => {
     await new Promise((resolve) => setTimeout(resolve, 10));
   });
 
+  it('returns latency in coverageResult', async () => {
+    const { backend, fetchMock } = setup();
+
+    fetchMock.mockResolvedValueOnce({
+      status: 200,
+      json: jest.fn().mockResolvedValue({ coverageId: 'coverageId' }),
+    } as unknown as Response);
+
+    const result = { status: 'covered', message: 'ok', reasonCode: 'E104' };
+    fetchMock.mockResolvedValueOnce({
+      status: 200,
+      json: jest.fn().mockResolvedValue(result),
+    } as unknown as Response);
+
+    let nowValue = 1000;
+    const latencyMs = 123;
+    const nowSpy = jest.spyOn(Date, 'now').mockImplementation(() => {
+      const val = nowValue;
+      nowValue += latencyMs;
+      return val;
+    });
+
+    const txMeta = generateMockTxMeta();
+    const coverageResult = await backend.checkCoverage({ txMeta });
+    expect(coverageResult.metrics.latency).toBe(latencyMs);
+
+    nowSpy.mockRestore();
+  });
+
+  it('returns latency in signatureCoverageResult', async () => {
+    const { backend, fetchMock } = setup();
+
+    fetchMock.mockResolvedValueOnce({
+      status: 200,
+      json: jest.fn().mockResolvedValue({ coverageId: 'coverageId' }),
+    } as unknown as Response);
+
+    const result = { status: 'covered', message: 'ok', reasonCode: 'E104' };
+    fetchMock.mockResolvedValueOnce({
+      status: 200,
+      json: jest.fn().mockResolvedValue(result),
+    } as unknown as Response);
+
+    let nowValue = 2000;
+    const latencyMs = 456;
+    const nowSpy = jest.spyOn(Date, 'now').mockImplementation(() => {
+      const val = nowValue;
+      nowValue += latencyMs;
+      return val;
+    });
+
+    const signatureRequest = generateMockSignatureRequest();
+    const coverageResult = await backend.checkSignatureCoverage({
+      signatureRequest,
+    });
+    expect(coverageResult.metrics.latency).toBe(latencyMs);
+
+    nowSpy.mockRestore();
+  });
+
   describe('checkSignatureCoverage', () => {
     it('should check signature coverage', async () => {
       const { backend, fetchMock, getAccessToken } = setup();
@@ -209,10 +308,16 @@ describe('ShieldRemoteBackend', () => {
       const coverageResult = await backend.checkSignatureCoverage({
         signatureRequest,
       });
-      expect(coverageResult).toStrictEqual({
+      expect({
+        coverageId: coverageResult.coverageId,
+        message: result.message,
+        reasonCode: result.reasonCode,
+        status: result.status,
+      }).toStrictEqual({
         coverageId,
         ...result,
       });
+      expect(typeof coverageResult.metrics.latency).toBe('number');
       expect(fetchMock).toHaveBeenCalledTimes(2);
       expect(getAccessToken).toHaveBeenCalledTimes(2);
     });

packages/shield-controller/src/backend.ts

@@ -57,6 +57,9 @@ export type GetCoverageResultResponse = {
   message?: string;
   reasonCode?: string;
   status: CoverageStatus;
+  metrics: {
+    latency?: number;
+  };
 };
 
 export class ShieldRemoteBackend implements ShieldBackend {
@@ -117,6 +120,7 @@ export class ShieldRemoteBackend implements ShieldBackend {
       message: coverageResult.message,
       reasonCode: coverageResult.reasonCode,
       status: coverageResult.status,
+      metrics: coverageResult.metrics,
     };
   }
 
@@ -143,6 +147,7 @@ export class ShieldRemoteBackend implements ShieldBackend {
       message: coverageResult.message,
       reasonCode: coverageResult.reasonCode,
       status: coverageResult.status,
+      metrics: coverageResult.metrics,
     };
   }
 
@@ -220,15 +225,20 @@ export class ShieldRemoteBackend implements ShieldBackend {
 
     const headers = await this.#createHeaders();
 
+    // Start measuring total end-to-end latency including retries and delays
+    const startTime = Date.now();
+
     const getCoverageResultFn = async (signal: AbortSignal) => {
       const res = await this.#fetch(coverageResultUrl, {
         method: 'POST',
         headers,
         body: JSON.stringify(reqBody),
         signal,
       });
+
       if (res.status === 200) {
-        return (await res.json()) as GetCoverageResultResponse;
+        // Return the result without latency here - we'll add total latency after polling completes
+        return (await res.json()) as Omit<GetCoverageResultResponse, 'metrics'>;
       }
 
       // parse the error message from the response body
@@ -242,7 +252,19 @@ export class ShieldRemoteBackend implements ShieldBackend {
       throw new HttpError(res.status, errorMessage);
     };
 
-    return this.#pollingPolicy.start(requestId, getCoverageResultFn);
+    const result = await this.#pollingPolicy.start(
+      requestId,
+      getCoverageResultFn,
+    );
+
+    // Calculate total end-to-end latency including all retries and delays
+    const now = Date.now();
+    const totalLatency = now - startTime;
+
+    return {
+      ...result,
+      metrics: { latency: totalLatency },
+    } as GetCoverageResultResponse;
   }
 
   async #createHeaders() {

packages/shield-controller/src/types.ts

@@ -6,6 +6,9 @@ export type CoverageResult = {
   message?: string;
   reasonCode?: string;
   status: CoverageStatus;
+  metrics: {
+    latency?: number;
+  };
 };
 
 export const coverageStatuses = ['covered', 'malicious', 'unknown'] as const;