feat: shared event emitter (#3241)

src/lib/db/event-store.ts

@@ -3,9 +3,10 @@ import { LogProvider, Logger } from '../logger';
 import { IEventStore } from '../types/stores/event-store';
 import { ITag } from '../types/model';
 import { SearchEventsSchema } from '../openapi/spec/search-events-schema';
-import { AnyEventEmitter } from '../util/anyEventEmitter';
+import { sharedEventEmitter } from '../util/anyEventEmitter';
 import { Db } from './db';
 import { Knex } from 'knex';
+import EventEmitter from 'events';
 
 const EVENT_COLUMNS = [
     'id',
@@ -76,13 +77,16 @@ export interface IEventTable {
 
 const TABLE = 'events';
 
-class EventStore extends AnyEventEmitter implements IEventStore {
+class EventStore implements IEventStore {
     private db: Db;
 
+    // only one shared event emitter should exist across all event store instances
+    private eventEmitter: EventEmitter = sharedEventEmitter;
+
     private logger: Logger;
 
+    // a new DB has to be injected per transaction
     constructor(db: Db, getLogger: LogProvider) {
-        super();
         this.db = db;
         this.logger = getLogger('lib/db/event-store.ts');
     }
@@ -93,7 +97,9 @@ class EventStore extends AnyEventEmitter implements IEventStore {
                 .insert(this.eventToDbRow(event))
                 .returning(EVENT_COLUMNS);
             const savedEvent = this.rowToEvent(rows[0]);
-            process.nextTick(() => this.emit(event.type, savedEvent));
+            process.nextTick(() =>
+                this.eventEmitter.emit(event.type, savedEvent),
+            );
         } catch (error: unknown) {
             this.logger.warn(`Failed to store "${event.type}" event: ${error}`);
         }
@@ -136,7 +142,7 @@ class EventStore extends AnyEventEmitter implements IEventStore {
                 .returning(EVENT_COLUMNS);
             const savedEvents = savedRows.map(this.rowToEvent);
             process.nextTick(() =>
-                savedEvents.forEach((e) => this.emit(e.type, e)),
+                savedEvents.forEach((e) => this.eventEmitter.emit(e.type, e)),
             );
         } catch (error: unknown) {
             this.logger.warn(`Failed to store events: ${error}`);
@@ -330,6 +336,28 @@ class EventStore extends AnyEventEmitter implements IEventStore {
             environment: e.environment,
         };
     }
+
+    setMaxListeners(number: number): EventEmitter {
+        return this.eventEmitter.setMaxListeners(number);
+    }
+
+    on(
+        eventName: string | symbol,
+        listener: (...args: any[]) => void,
+    ): EventEmitter {
+        return this.eventEmitter.on(eventName, listener);
+    }
+
+    emit(eventName: string | symbol, ...args: any[]): boolean {
+        return this.eventEmitter.emit(eventName, ...args);
+    }
+
+    off(
+        eventName: string | symbol,
+        listener: (...args: any[]) => void,
+    ): EventEmitter {
+        return this.eventEmitter.off(eventName, listener);
+    }
 }
 
 export default EventStore;

src/lib/event-hook.ts

@@ -9,7 +9,7 @@ import {
 
 export const addEventHook = (
     eventHook: EventHook,
-    eventStore: EventEmitter,
+    eventStore: Pick<EventEmitter, 'on'>,
 ): void => {
     eventStore.on(FEATURE_CREATED, (data) => {
         eventHook(FEATURE_CREATED, data);

src/lib/features/export-import-toggles/createExportImportService.ts

@@ -1,5 +1,5 @@
 import { Db } from '../../db/db';
-import { IEventStore, IUnleashConfig } from '../../types';
+import { IUnleashConfig } from '../../types';
 import ExportImportService from './export-import-service';
 import { ImportTogglesStore } from './import-toggles-store';
 import FeatureToggleStore from '../../db/feature-toggle-store';
@@ -37,6 +37,7 @@ import FakeEventStore from '../../../test/fixtures/fake-event-store';
 import FakeFeatureStrategiesStore from '../../../test/fixtures/fake-feature-strategies-store';
 import FakeFeatureEnvironmentStore from '../../../test/fixtures/fake-feature-environment-store';
 import FakeStrategiesStore from '../../../test/fixtures/fake-strategies-store';
+import EventStore from '../../db/event-store';
 
 export const createFakeExportImportTogglesService = (
     config: IUnleashConfig,
@@ -111,7 +112,6 @@ export const createFakeExportImportTogglesService = (
 export const createExportImportTogglesService = (
     db: Db,
     config: IUnleashConfig,
-    eventStore: IEventStore,
 ): ExportImportService => {
     const { eventBus, getLogger, flagResolver } = config;
     const importTogglesStore = new ImportTogglesStore(db);
@@ -139,12 +139,9 @@ export const createExportImportTogglesService = (
         eventBus,
         getLogger,
     );
+    const eventStore = new EventStore(db, getLogger);
     const accessService = createAccessService(db, config);
-    const featureToggleService = createFeatureToggleService(
-        db,
-        config,
-        eventStore,
-    );
+    const featureToggleService = createFeatureToggleService(db, config);
 
     const featureTagService = new FeatureTagService(
         {

src/lib/features/feature-toggle/createFeatureToggleService.ts

@@ -18,7 +18,7 @@ import { AccessStore } from '../../db/access-store';
 import RoleStore from '../../db/role-store';
 import EnvironmentStore from '../../db/environment-store';
 import { Db } from '../../db/db';
-import { IEventStore, IUnleashConfig } from '../../types';
+import { IUnleashConfig } from '../../types';
 import FakeEventStore from '../../../test/fixtures/fake-event-store';
 import FakeFeatureStrategiesStore from '../../../test/fixtures/fake-feature-strategies-store';
 import FakeFeatureToggleStore from '../../../test/fixtures/fake-feature-toggle-store';
@@ -33,11 +33,11 @@ import { FakeAccountStore } from '../../../test/fixtures/fake-account-store';
 import FakeAccessStore from '../../../test/fixtures/fake-access-store';
 import FakeRoleStore from '../../../test/fixtures/fake-role-store';
 import FakeEnvironmentStore from '../../../test/fixtures/fake-environment-store';
+import EventStore from '../../db/event-store';
 
 export const createFeatureToggleService = (
     db: Db,
     config: IUnleashConfig,
-    eventStore: IEventStore,
 ): FeatureToggleService => {
     const { getLogger, eventBus, flagResolver } = config;
     const featureStrategiesStore = new FeatureStrategiesStore(
@@ -73,6 +73,7 @@ export const createFeatureToggleService = (
     const accessStore = new AccessStore(db, eventBus, getLogger);
     const roleStore = new RoleStore(db, eventBus, getLogger);
     const environmentStore = new EnvironmentStore(db, eventBus, getLogger);
+    const eventStore = new EventStore(db, getLogger);
     const groupService = new GroupService(
         { groupStore, eventStore, accountStore },
         { getLogger },

src/lib/services/index.ts

@@ -164,10 +164,10 @@ export const createServices = (
 
     // TODO: this is a temporary seam to enable packaging by feature
     const exportImportService = db
-        ? createExportImportTogglesService(db, config, stores.eventStore)
+        ? createExportImportTogglesService(db, config)
         : createFakeExportImportTogglesService(config);
     const transactionalExportImportService = (txDb: Knex.Transaction) =>
-        createExportImportTogglesService(txDb, config, stores.eventStore);
+        createExportImportTogglesService(txDb, config);
     const userSplashService = new UserSplashService(stores, config);
     const openApiService = new OpenApiService(config);
     const clientSpecService = new ClientSpecService(config);

src/lib/types/stores/event-store.ts

@@ -4,7 +4,9 @@ import { SearchEventsSchema } from '../../openapi/spec/search-events-schema';
 import EventEmitter from 'events';
 import { IQueryOperations } from 'lib/db/event-store';
 
-export interface IEventStore extends Store<IEvent, number>, EventEmitter {
+export interface IEventStore
+    extends Store<IEvent, number>,
+        Pick<EventEmitter, 'on' | 'setMaxListeners' | 'emit' | 'off'> {
     store(event: IBaseEvent): Promise<void>;
     batchStore(events: IBaseEvent[]): Promise<void>;
     getEvents(): Promise<IEvent[]>;

src/lib/util/anyEventEmitter.ts

@@ -10,3 +10,5 @@ export class AnyEventEmitter extends EventEmitter {
         return super.emit(type, ...args) || super.emit('', ...args);
     }
 }
+
+export const sharedEventEmitter = new AnyEventEmitter();

src/test/fixtures/fake-event-store.ts

@@ -1,28 +1,30 @@
 import { IEventStore } from '../../lib/types/stores/event-store';
 import { IEvent } from '../../lib/types/events';
-import { AnyEventEmitter } from '../../lib/util/anyEventEmitter';
+import { sharedEventEmitter } from '../../lib/util/anyEventEmitter';
 import { IQueryOperations } from 'lib/db/event-store';
 import { SearchEventsSchema } from '../../lib/openapi';
+import EventEmitter from 'events';
 
-class FakeEventStore extends AnyEventEmitter implements IEventStore {
+class FakeEventStore implements IEventStore {
     events: IEvent[];
 
+    private eventEmitter: EventEmitter = sharedEventEmitter;
+
     constructor() {
-        super();
-        this.setMaxListeners(0);
+        this.eventEmitter.setMaxListeners(0);
         this.events = [];
     }
 
     store(event: IEvent): Promise<void> {
         this.events.push(event);
-        this.emit(event.type, event);
+        this.eventEmitter.emit(event.type, event);
         return Promise.resolve();
     }
 
     batchStore(events: IEvent[]): Promise<void> {
         events.forEach((event) => {
             this.events.push(event);
-            this.emit(event.type, event);
+            this.eventEmitter.emit(event.type, event);
         });
         return Promise.resolve();
     }
@@ -88,6 +90,28 @@ class FakeEventStore extends AnyEventEmitter implements IEventStore {
         if (operations) return [];
         return [];
     }
+
+    setMaxListeners(number: number): EventEmitter {
+        return this.eventEmitter.setMaxListeners(number);
+    }
+
+    on(
+        eventName: string | symbol,
+        listener: (...args: any[]) => void,
+    ): EventEmitter {
+        return this.eventEmitter.on(eventName, listener);
+    }
+
+    emit(eventName: string | symbol, ...args: any[]): boolean {
+        return this.eventEmitter.emit(eventName, ...args);
+    }
+
+    off(
+        eventName: string | symbol,
+        listener: (...args: any[]) => void,
+    ): EventEmitter {
+        return this.eventEmitter.off(eventName, listener);
+    }
 }
 
 module.exports = FakeEventStore;