fix: Configuration revision service singleton (#6493)

src/lib/features/feature-toggle/configuration-revision-service.ts

@@ -1,4 +1,3 @@
-import { EventEmitter } from 'stream';
 import { Logger } from '../../logger';
 import {
     IEventStore,
@@ -6,10 +5,13 @@ import {
     IUnleashConfig,
     IUnleashStores,
 } from '../../types';
+import EventEmitter from 'events';
 
 export const UPDATE_REVISION = 'UPDATE_REVISION';
 
 export default class ConfigurationRevisionService extends EventEmitter {
+    private static instance: ConfigurationRevisionService;
+
     private logger: Logger;
 
     private eventStore: IEventStore;
@@ -18,7 +20,7 @@ export default class ConfigurationRevisionService extends EventEmitter {
 
     private flagResolver: IFlagResolver;
 
-    constructor(
+    private constructor(
         { eventStore }: Pick<IUnleashStores, 'eventStore'>,
         {
             getLogger,
@@ -32,6 +34,23 @@ export default class ConfigurationRevisionService extends EventEmitter {
         this.revisionId = 0;
     }
 
+    static getInstance(
+        { eventStore }: Pick<IUnleashStores, 'eventStore'>,
+        {
+            getLogger,
+            flagResolver,
+        }: Pick<IUnleashConfig, 'getLogger' | 'flagResolver'>,
+    ) {
+        if (!ConfigurationRevisionService.instance) {
+            ConfigurationRevisionService.instance =
+                new ConfigurationRevisionService(
+                    { eventStore },
+                    { getLogger, flagResolver },
+                );
+        }
+        return ConfigurationRevisionService.instance;
+    }
+
     async getMaxRevisionId(): Promise<number> {
         if (this.revisionId > 0) {
             return this.revisionId;

src/lib/proxy/createProxyService.ts

@@ -10,12 +10,10 @@ import {
     createFeatureToggleService,
 } from '../features';
 import ConfigurationRevisionService from '../features/feature-toggle/configuration-revision-service';
-import EventStore from '../features/events/event-store';
 import { GlobalFrontendApiCache } from './global-frontend-api-cache';
 import ClientFeatureToggleReadModel from './client-feature-toggle-read-model';
 import { FakeSegmentReadModel } from '../features/segment/fake-segment-read-model';
 import FakeSettingStore from '../../test/fixtures/fake-setting-store';
-import FakeEventStore from '../../test/fixtures/fake-event-store';
 import FakeClientFeatureToggleReadModel from './fake-client-feature-toggle-read-model';
 import { IUnleashConfig } from '../types';
 import { Db } from '../db/db';
@@ -25,6 +23,7 @@ export const createProxyService = (
     config: IUnleashConfig,
     // client metrics service needs to be shared because it uses in-memory cache
     clientMetricsServiceV2: ClientMetricsServiceV2,
+    configurationRevisionService: ConfigurationRevisionService,
 ): ProxyService => {
     const segmentReadModel = new SegmentReadModel(db);
     const settingStore = new SettingStore(db, config.getLogger);
@@ -36,15 +35,6 @@ export const createProxyService = (
     );
     // TODO: remove this dependency after we migrate frontend API
     const featureToggleServiceV2 = createFeatureToggleService(db, config);
-    const eventStore = new EventStore(
-        db,
-        config.getLogger,
-        config.flagResolver,
-    );
-    const configurationRevisionService = new ConfigurationRevisionService(
-        { eventStore },
-        config,
-    );
     const clientFeatureToggleReadModel = new ClientFeatureToggleReadModel(
         db,
         config.eventBus,
@@ -71,6 +61,7 @@ export const createProxyService = (
 export const createFakeProxyService = (
     config: IUnleashConfig,
     clientMetricsServiceV2: ClientMetricsServiceV2,
+    configurationRevisionService: ConfigurationRevisionService,
 ): ProxyService => {
     const segmentReadModel = new FakeSegmentReadModel();
     const settingStore = new FakeSettingStore();
@@ -82,11 +73,6 @@ export const createFakeProxyService = (
     );
     // TODO: remove this dependency after we migrate frontend API
     const featureToggleServiceV2 = createFakeFeatureToggleService(config);
-    const eventStore = new FakeEventStore();
-    const configurationRevisionService = new ConfigurationRevisionService(
-        { eventStore },
-        config,
-    );
     const clientFeatureToggleReadModel = new FakeClientFeatureToggleReadModel();
     const globalFrontendApiCache = new GlobalFrontendApiCache(
         config,

src/lib/services/index.ts

@@ -111,9 +111,10 @@ import {
 import { InactiveUsersService } from '../users/inactive/inactive-users-service';
 import { SegmentReadModel } from '../features/segment/segment-read-model';
 import { FakeSegmentReadModel } from '../features/segment/fake-segment-read-model';
-import ClientFeatureToggleReadModel from '../proxy/client-feature-toggle-read-model';
+import {
-import FakeClientFeatureToggleReadModel from '../proxy/fake-client-feature-toggle-read-model';
+    createFakeProxyService,
-import { GlobalFrontendApiCache } from '../proxy/global-frontend-api-cache';
+    createProxyService,
+} from '../proxy/createProxyService';
 
 export const createServices = (
     stores: IUnleashStores,
@@ -287,35 +288,24 @@ export const createServices = (
         segmentReadModel,
     );
 
-    const configurationRevisionService = new ConfigurationRevisionService(
+    const configurationRevisionService =
-        stores,
+        ConfigurationRevisionService.getInstance(stores, config);
-        config,
-    );
 
     const clientFeatureToggleService = db
         ? createClientFeatureToggleService(db, config)
         : createFakeClientFeatureToggleService(config);
 
-    const clientFeatureToggleReadModel = db
+    const proxyService = db
-        ? new ClientFeatureToggleReadModel(db, config.eventBus)
+        ? createProxyService(
-        : new FakeClientFeatureToggleReadModel();
+              db,
-    const globalFrontendApiCache = new GlobalFrontendApiCache(
+              config,
+              clientMetricsServiceV2,
+              configurationRevisionService,
+          )
+        : createFakeProxyService(
               config,
-        segmentReadModel,
-        clientFeatureToggleReadModel,
-        configurationRevisionService,
-    );
-
-    const proxyService = new ProxyService(
-        config,
-        stores,
-        {
-            featureToggleServiceV2,
               clientMetricsServiceV2,
-            settingService,
               configurationRevisionService,
-        },
-        globalFrontendApiCache,
           );
 
     const edgeService = new EdgeService({ apiTokenService }, config);