fix: measure frontend times only when flag enabled (#6535)

Moving to controller level to measure only for flag. Other option would
have been to check flag also at service.

src/lib/features/frontend-api/frontend-api-controller.ts

@@ -23,6 +23,8 @@ import rateLimit from 'express-rate-limit';
 import { minutesToMilliseconds } from 'date-fns';
 import isEqual from 'lodash.isequal';
 import { diff } from 'json-diff';
+import metricsHelper from '../../util/metrics-helper';
+import { FUNCTION_TIME } from '../../metric-events';
 
 interface ApiUserRequest<
     PARAM = any,
@@ -43,11 +45,19 @@ export default class FrontendAPIController extends Controller {
 
     private services: Services;
 
+    private timer: Function;
+
     constructor(config: IUnleashConfig, services: Services) {
         super(config);
         this.logger = config.getLogger('frontend-api-controller.ts');
         this.services = services;
 
+        this.timer = (functionName) =>
+            metricsHelper.wrapTimer(config.eventBus, FUNCTION_TIME, {
+                className: 'FrontendAPIController',
+                functionName,
+            });
+
         // Support CORS requests for the frontend endpoints.
         // Preflight requests are handled in `app.ts`.
         this.app.use(corsOriginMiddleware(services, config));
@@ -181,14 +191,8 @@ export default class FrontendAPIController extends Controller {
         if (this.config.flagResolver.isEnabled('globalFrontendApiCache')) {
             const context = FrontendAPIController.createContext(req);
             [toggles, newToggles] = await Promise.all([
-                this.services.frontendApiService.getFrontendApiFeatures(
+                this.getTimedFrontendApiFeatures(req.user, context),
-                    req.user,
+                this.getTimedNewFrontendApiFeatures(req.user, context),
-                    context,
-                ),
-                this.services.frontendApiService.getNewFrontendApiFeatures(
-                    req.user,
-                    context,
-                ),
             ]);
             const sortedToggles = toggles.sort((a, b) =>
                 a.name.localeCompare(b.name),
@@ -233,6 +237,28 @@ export default class FrontendAPIController extends Controller {
         );
     }
 
+    private async getTimedFrontendApiFeatures(req, context) {
+        const stopTimer = this.timer('getFrontendApiFeatures');
+        const features =
+            await this.services.frontendApiService.getFrontendApiFeatures(
+                req.user,
+                context,
+            );
+        stopTimer();
+        return features;
+    }
+
+    private async getTimedNewFrontendApiFeatures(req, context) {
+        const stopTimer = this.timer('getNewFrontendApiFeatures');
+        const features =
+            await this.services.frontendApiService.getNewFrontendApiFeatures(
+                req.user,
+                context,
+            );
+        stopTimer();
+        return features;
+    }
+
     private async registerFrontendApiMetrics(
         req: ApiUserRequest<unknown, unknown, ClientMetricsSchema>,
         res: Response,

src/lib/features/frontend-api/frontend-api-service.ts

@@ -16,14 +16,12 @@ import {
 import { validateOrigins } from '../../util';
 import { BadDataError, InvalidTokenError } from '../../error';
 import {
-    FUNCTION_TIME,
     FRONTEND_API_REPOSITORY_CREATED,
     PROXY_REPOSITORY_CREATED,
 } from '../../metric-events';
 import { FrontendApiRepository } from './frontend-api-repository';
 import { GlobalFrontendApiCache } from './global-frontend-api-cache';
 import { ProxyRepository } from './proxy-repository';
-import metricsHelper from '../../util/metrics-helper';
 
 export type Config = Pick<
     IUnleashConfig,
@@ -63,8 +61,6 @@ export class FrontendApiService {
 
     private cachedFrontendSettings?: FrontendSettings;
 
-    private timer: Function;
-
     constructor(
         config: Config,
         stores: Stores,
@@ -76,19 +72,12 @@ export class FrontendApiService {
         this.stores = stores;
         this.services = services;
         this.globalFrontendApiCache = globalFrontendApiCache;
-
-        this.timer = (functionName) =>
-            metricsHelper.wrapTimer(config.eventBus, FUNCTION_TIME, {
-                className: 'FrontendApiService',
-                functionName,
-            });
     }
 
     async getFrontendApiFeatures(
         token: IApiUser,
         context: Context,
     ): Promise<FrontendApiFeatureSchema[]> {
-        const stopTimer = this.timer('getFrontendApiFeatures');
         const client = await this.clientForFrontendApiToken(token);
         const definitions = client.getFeatureToggleDefinitions() || [];
         const sessionId = context.sessionId || String(Math.random());
@@ -109,7 +98,6 @@ export class FrontendApiService {
                 }),
                 impressionData: Boolean(feature.impressionData),
             }));
-        stopTimer();
         return resultDefinitions;
     }
 
@@ -117,7 +105,6 @@ export class FrontendApiService {
         token: IApiUser,
         context: Context,
     ): Promise<FrontendApiFeatureSchema[]> {
-        const stopTimer = this.timer('getNewFrontendApiFeatures');
         const client = await this.newClientForFrontendApiToken(token);
         const definitions = client.getFeatureToggleDefinitions() || [];
         const sessionId = context.sessionId || String(Math.random());
@@ -139,7 +126,6 @@ export class FrontendApiService {
                 }),
                 impressionData: Boolean(feature.impressionData),
             }));
-        stopTimer();
         return resultDefinitions;
     }