Fix/embedded proxy memory leak (#2345)

* Fixes a memory leak where events would trigger the data polling to restart. Any event would setup another polling interval, which would strain our database. Separated the logic for fetching the data and the polling, and made sure that the polling was only initialized once.

src/lib/proxy/proxy-repository.ts

@@ -73,7 +73,7 @@ export class ProxyRepository
     }
 
     async start(): Promise<void> {
-        await this.loadDataForToken();
+        await this.dataPolling();
 
         // Reload cached token data whenever something relevant has changed.
         // For now, simply reload all the data on any EventStore event.
@@ -88,11 +88,15 @@ export class ProxyRepository
         clearTimeout(this.timer);
     }
 
-    private async loadDataForToken() {
+    private async dataPolling() {
         this.timer = setTimeout(async () => {
-            await this.loadDataForToken();
+            await this.dataPolling();
         }, this.randomizeDelay(this.interval, this.interval * 2)).unref();
 
+        await this.loadDataForToken();
+    }
+
+    private async loadDataForToken() {
         try {
             this.features = await this.featuresForToken();
             this.segments = await this.segmentsForToken();

src/test/e2e/api/proxy/proxy.e2e.test.ts

@@ -10,6 +10,7 @@ import {
 import { startOfHour } from 'date-fns';
 import { IConstraint, IStrategyConfig } from '../../../../lib/types/model';
 import { ProxyRepository } from '../../../../lib/proxy/proxy-repository';
+import { FEATURE_UPDATED } from '../../../../lib/types/events';
 
 let app: IUnleashTest;
 let db: ITestDb;
@@ -898,3 +899,33 @@ test('Should change fetch interval', async () => {
     expect(spy.mock.calls.length > 30).toBe(true);
     jest.useRealTimers();
 });
+
+test('Should not recursively set off timers on events', async () => {
+    jest.useFakeTimers();
+
+    const frontendToken = await createApiToken(ApiTokenType.FRONTEND);
+    const user = await app.services.apiTokenService.getUserForToken(
+        frontendToken.secret,
+    );
+
+    const spy = jest.spyOn(ProxyRepository.prototype as any, 'dataPolling');
+    const proxyRepository = new ProxyRepository(
+        {
+            getLogger,
+            frontendApi: { refreshIntervalInMs: 5000 },
+        },
+        db.stores,
+        app.services,
+        user,
+    );
+
+    await proxyRepository.start();
+
+    db.stores.eventStore.emit(FEATURE_UPDATED);
+
+    jest.advanceTimersByTime(10000);
+
+    proxyRepository.stop();
+    expect(spy.mock.calls.length < 3).toBe(true);
+    jest.useRealTimers();
+});