[FSSDK-11513] limit number of events in the eventStore (#1053)

raju-opti · web-flow · commit 4d2a4e12bcbb · 2025-05-15T23:50:42.000+06:00
diff --git a/lib/event_processor/batch_event_processor.spec.ts b/lib/event_processor/batch_event_processor.spec.ts
@@ -16,17 +16,18 @@
 import { expect, describe, it, vi, beforeEach, afterEach, MockInstance } from 'vitest';
 
 import { EventWithId, BatchEventProcessor, LOGGER_NAME } from './batch_event_processor';
-import { getMockSyncCache } from '../tests/mock/mock_cache';
+import { getMockAsyncCache, getMockSyncCache } from '../tests/mock/mock_cache';
 import { createImpressionEvent } from '../tests/mock/create_event';
 import { ProcessableEvent } from './event_processor';
 import { buildLogEvent } from './event_builder/log_event';
-import { resolvablePromise } from '../utils/promise/resolvablePromise';
+import { ResolvablePromise, resolvablePromise } from '../utils/promise/resolvablePromise';
 import { advanceTimersByTime } from  '../tests/testUtils';
 import { getMockLogger } from '../tests/mock/mock_logger';
 import { getMockRepeater } from '../tests/mock/mock_repeater';
 import * as retry from '../utils/executor/backoff_retry_runner';
 import { ServiceState, StartupLog } from '../service';
 import { LogLevel } from '../logging/logger';
+import { IdGenerator } from '../utils/id_generator';
 
 const getMockDispatcher = () => {
   return {
@@ -366,6 +367,160 @@ describe('BatchEventProcessor', async () => {
 
       expect(events).toEqual(eventsInStore);
     });
+
+    it('should not store the event in the eventStore but still dispatch if the \
+        number of pending events is greater than the limit', async () => {
+      const eventDispatcher = getMockDispatcher();
+      const mockDispatch: MockInstance<typeof eventDispatcher.dispatchEvent> = eventDispatcher.dispatchEvent;
+      mockDispatch.mockResolvedValue(resolvablePromise().promise);
+
+      const eventStore = getMockSyncCache<EventWithId>();
+
+      const idGenerator = new IdGenerator();
+
+      for (let i = 0; i < 505; i++) {
+        const event = createImpressionEvent(`id-${i}`);
+        const cacheId = idGenerator.getId();
+        await eventStore.set(cacheId, { id: cacheId, event });
+      }
+
+      expect(eventStore.size()).toEqual(505);
+
+      const processor = new BatchEventProcessor({
+        eventDispatcher,
+        dispatchRepeater: getMockRepeater(),
+        batchSize: 1,
+        eventStore,
+      });
+
+      processor.start();
+      await processor.onRunning();
+
+      const events: ProcessableEvent[] = [];
+      for(let i = 0; i < 2; i++) {
+        const event = createImpressionEvent(`id-${i}`);
+        events.push(event);
+        await processor.process(event)
+      }
+
+      expect(eventStore.size()).toEqual(505);
+      expect(eventDispatcher.dispatchEvent).toHaveBeenCalledTimes(507);
+      expect(eventDispatcher.dispatchEvent.mock.calls[505][0]).toEqual(buildLogEvent([events[0]]));
+      expect(eventDispatcher.dispatchEvent.mock.calls[506][0]).toEqual(buildLogEvent([events[1]]));
+    });
+
+    it('should store events in the eventStore when the number of events in the store\
+        becomes lower than the limit', async () => {
+      const eventDispatcher = getMockDispatcher();
+
+      const dispatchResponses: ResolvablePromise<any>[] = [];
+
+      const mockDispatch: MockInstance<typeof eventDispatcher.dispatchEvent> = eventDispatcher.dispatchEvent;
+      mockDispatch.mockImplementation((arg) => {
+        const dispatchResponse = resolvablePromise();
+        dispatchResponses.push(dispatchResponse);
+        return dispatchResponse.promise;
+      });
+
+      const eventStore = getMockSyncCache<EventWithId>();
+
+      const idGenerator = new IdGenerator();
+
+      for (let i = 0; i < 502; i++) {
+        const event = createImpressionEvent(`id-${i}`);
+        const cacheId = String(i);
+        await eventStore.set(cacheId, { id: cacheId, event });
+      }
+
+      expect(eventStore.size()).toEqual(502);
+
+      const processor = new BatchEventProcessor({
+        eventDispatcher,
+        dispatchRepeater: getMockRepeater(),
+        batchSize: 1,
+        eventStore,
+      });
+
+      processor.start();
+      await processor.onRunning();
+
+      let events: ProcessableEvent[] = [];
+      for(let i = 0; i < 2; i++) {
+        const event = createImpressionEvent(`id-${i + 502}`);
+        events.push(event);
+        await processor.process(event)
+      }
+
+      expect(eventStore.size()).toEqual(502);
+      expect(eventDispatcher.dispatchEvent).toHaveBeenCalledTimes(504);
+
+      expect(eventDispatcher.dispatchEvent.mock.calls[502][0]).toEqual(buildLogEvent([events[0]]));
+      expect(eventDispatcher.dispatchEvent.mock.calls[503][0]).toEqual(buildLogEvent([events[1]]));
+
+      // resolve the dispatch for events not saved in the store
+      dispatchResponses[502].resolve({ statusCode: 200 });
+      dispatchResponses[503].resolve({ statusCode: 200 });
+
+      await exhaustMicrotasks();
+      expect(eventStore.size()).toEqual(502);
+
+      // resolve the dispatch for 3 events in store, making the store size 499 which is lower than the limit
+      dispatchResponses[0].resolve({ statusCode: 200 });
+      dispatchResponses[1].resolve({ statusCode: 200 });
+      dispatchResponses[2].resolve({ statusCode: 200 });
+
+      await exhaustMicrotasks();
+      expect(eventStore.size()).toEqual(499);
+
+      // process 2 more events
+      events = [];
+      for(let i = 0; i < 2; i++) {
+        const event = createImpressionEvent(`id-${i + 504}`);
+        events.push(event);
+        await processor.process(event)
+      }
+
+      expect(eventStore.size()).toEqual(500);
+      expect(eventDispatcher.dispatchEvent).toHaveBeenCalledTimes(506);
+      expect(eventDispatcher.dispatchEvent.mock.calls[504][0]).toEqual(buildLogEvent([events[0]]));
+      expect(eventDispatcher.dispatchEvent.mock.calls[505][0]).toEqual(buildLogEvent([events[1]]));      
+    });
+
+    it('should still dispatch events even if the store save fails', async () => {
+      const eventDispatcher = getMockDispatcher();
+      const mockDispatch: MockInstance<typeof eventDispatcher.dispatchEvent> = eventDispatcher.dispatchEvent;
+      mockDispatch.mockResolvedValue({});
+
+      const eventStore = getMockAsyncCache<EventWithId>();
+      // Simulate failure in saving to store
+      eventStore.set = vi.fn().mockRejectedValue(new Error('Failed to save'));
+
+      const dispatchRepeater = getMockRepeater();
+
+      const processor = new BatchEventProcessor({
+        eventDispatcher,
+        dispatchRepeater,
+        batchSize: 100,
+        eventStore,
+      });
+
+      processor.start();
+      await processor.onRunning();
+
+      const events: ProcessableEvent[] = [];
+      for(let i = 0; i < 10; i++) {
+        const event = createImpressionEvent(`id-${i}`);
+        events.push(event);
+        await processor.process(event)
+      }
+
+      expect(eventDispatcher.dispatchEvent).toHaveBeenCalledTimes(0);
+
+      await dispatchRepeater.execute(0);
+
+      expect(eventDispatcher.dispatchEvent).toHaveBeenCalledTimes(1);
+      expect(eventDispatcher.dispatchEvent.mock.calls[0][0]).toEqual(buildLogEvent(events));
+    });
   });
 
   it('should dispatch events when dispatchRepeater is triggered', async () => {
diff --git a/lib/event_processor/batch_event_processor.ts b/lib/event_processor/batch_event_processor.ts
@@ -18,10 +18,10 @@ import { EventProcessor, ProcessableEvent } from "./event_processor";
 import { getBatchedAsync, getBatchedSync, Store } from "../utils/cache/store";
 import { EventDispatcher, EventDispatcherResponse, LogEvent } from "./event_dispatcher/event_dispatcher";
 import { buildLogEvent } from "./event_builder/log_event";
-import { BackoffController, ExponentialBackoff, IntervalRepeater, Repeater } from "../utils/repeater/repeater";
+import { BackoffController, ExponentialBackoff, Repeater } from "../utils/repeater/repeater";
 import { LoggerFacade } from '../logging/logger';
 import { BaseService, ServiceState, StartupLog } from "../service";
-import { Consumer, Fn, Producer } from "../utils/type";
+import { Consumer, Fn, Maybe, Producer } from "../utils/type";
 import { RunResult, runWithRetry } from "../utils/executor/backoff_retry_runner";
 import { isSuccessStatusCode } from "../utils/http_request_handler/http_util";
 import { EventEmitter } from "../utils/event_emitter/event_emitter";
@@ -31,13 +31,16 @@ import { FAILED_TO_DISPATCH_EVENTS, SERVICE_NOT_RUNNING } from "error_message";
 import { OptimizelyError } from "../error/optimizly_error";
 import { sprintf } from "../utils/fns";
 import { SERVICE_STOPPED_BEFORE_RUNNING } from "../service";
+import { EVENT_STORE_FULL } from "../message/log_message";
 
 export const DEFAULT_MIN_BACKOFF = 1000;
 export const DEFAULT_MAX_BACKOFF = 32000;
+export const MAX_EVENTS_IN_STORE = 500;
 
 export type EventWithId = {
   id: string;
   event: ProcessableEvent;
+  notStored?: boolean;
 };
 
 export type RetryConfig = {
@@ -59,7 +62,7 @@ export type BatchEventProcessorConfig = {
 
 type EventBatch = {
   request: LogEvent,
-  ids: string[],
+  events: EventWithId[],
 }
 
 export const LOGGER_NAME = 'BatchEventProcessor';
@@ -70,11 +73,13 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
   private eventQueue: EventWithId[] = [];
   private batchSize: number;
   private eventStore?: Store<EventWithId>;
+  private eventCountInStore: Maybe<number> = undefined;
+  private maxEventsInStore: number = MAX_EVENTS_IN_STORE;
   private dispatchRepeater: Repeater;
   private failedEventRepeater?: Repeater;
   private idGenerator: IdGenerator = new IdGenerator();
   private runningTask: Map<string, RunResult<EventDispatcherResponse>> = new Map();
-  private dispatchingEventIds: Set<string> = new Set();
+  private dispatchingEvents: Map<string, EventWithId> = new Map();
   private eventEmitter: EventEmitter<{ dispatch: LogEvent }> = new EventEmitter();
   private retryConfig?: RetryConfig;
 
@@ -84,11 +89,13 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     this.closingEventDispatcher = config.closingEventDispatcher;
     this.batchSize = config.batchSize;
     this.eventStore = config.eventStore;
+
     this.retryConfig = config.retryConfig;
 
     this.dispatchRepeater = config.dispatchRepeater;
     this.dispatchRepeater.setTask(() => this.flush());
 
+    this.maxEventsInStore = Math.max(2 * config.batchSize, MAX_EVENTS_IN_STORE);
     this.failedEventRepeater = config.failedEventRepeater;
     this.failedEventRepeater?.setTask(() => this.retryFailedEvents());
     if (config.logger) {
@@ -111,7 +118,7 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     }
 
     const keys = (await this.eventStore.getKeys()).filter(
-      (k) => !this.dispatchingEventIds.has(k) && !this.eventQueue.find((e) => e.id === k)
+      (k) => !this.dispatchingEvents.has(k) && !this.eventQueue.find((e) => e.id === k)
     );
 
     const events = await (this.eventStore.operation === 'sync' ?
@@ -138,7 +145,7 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
            (currentBatch.length > 0 && !areEventContextsEqual(currentBatch[0].event, event.event))) {
         batches.push({
           request: buildLogEvent(currentBatch.map((e) => e.event)),
-          ids: currentBatch.map((e) => e.id),
+          events: currentBatch,
         });
         currentBatch = [];
       }
@@ -148,7 +155,7 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     if (currentBatch.length > 0) {
       batches.push({
         request: buildLogEvent(currentBatch.map((e) => e.event)),
-        ids: currentBatch.map((e) => e.id),
+        events: currentBatch,
       });
     }
 
@@ -163,15 +170,15 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     }
     
     const events: ProcessableEvent[] = [];
-    const ids: string[] = [];
+    const eventWithIds: EventWithId[] = [];
 
     this.eventQueue.forEach((event) => {
       events.push(event.event);
-      ids.push(event.id);
+      eventWithIds.push(event);
     });
 
     this.eventQueue = [];
-    return { request: buildLogEvent(events), ids };
+    return { request: buildLogEvent(events), events: eventWithIds };
   }
 
   private async executeDispatch(request: LogEvent, closing = false): Promise<EventDispatcherResponse> {
@@ -185,10 +192,10 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
   }
 
   private dispatchBatch(batch: EventBatch, closing: boolean): void {
-    const { request, ids } = batch;
+    const { request, events } = batch;
     
-    ids.forEach((id) => {
-      this.dispatchingEventIds.add(id);
+    events.forEach((event) => {
+      this.dispatchingEvents.set(event.id, event);
     });
 
     const runResult: RunResult<EventDispatcherResponse> = this.retryConfig
@@ -205,9 +212,11 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     this.runningTask.set(taskId, runResult);
 
     runResult.result.then((res) => {
-      ids.forEach((id) => {
-        this.dispatchingEventIds.delete(id);
-        this.eventStore?.remove(id);
+      events.forEach((event) => {
+        this.eventStore?.remove(event.id);
+        if (!event.notStored && this.eventCountInStore) {
+          this.eventCountInStore--;
+        }
       });
       return Promise.resolve();
     }).catch((err) => {
@@ -216,7 +225,7 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
       this.logger?.error(err);
     }).finally(() => {
       this.runningTask.delete(taskId);
-      ids.forEach((id) => this.dispatchingEventIds.delete(id));
+      events.forEach((event) => this.dispatchingEvents.delete(event.id));
     });
   }
 
@@ -235,12 +244,12 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
       return Promise.reject(new OptimizelyError(SERVICE_NOT_RUNNING, 'BatchEventProcessor'));
     }
 
-    const eventWithId = {
+    const eventWithId: EventWithId = {
       id: this.idGenerator.getId(),
       event: event,
     };
     
-    await this.eventStore?.set(eventWithId.id, eventWithId);
+    await this.storeEvent(eventWithId);
     
     if (this.eventQueue.length > 0 && !areEventContextsEqual(this.eventQueue[0].event, event)) {
       this.flush();
@@ -253,7 +262,35 @@ export class BatchEventProcessor extends BaseService implements EventProcessor {
     } else if (!this.dispatchRepeater.isRunning()) {
       this.dispatchRepeater.start();
     }
+  }
+
+  private async findEventCountInStore(): Promise<void> {
+    if (this.eventStore && this.eventCountInStore === undefined) {
+      try {
+        const keys = await this.eventStore.getKeys();
+        this.eventCountInStore = keys.length;
+      } catch (e) {
+        this.logger?.error(e);
+      }
+    }
+  }
 
+  private async storeEvent(eventWithId: EventWithId): Promise<void> {
+    await this.findEventCountInStore();
+    if (this.eventCountInStore !== undefined && this.eventCountInStore >= this.maxEventsInStore) {
+      this.logger?.info(EVENT_STORE_FULL, eventWithId.event.uuid);
+      eventWithId.notStored = true;
+      return;
+    }
+
+    await Promise.resolve(this.eventStore?.set(eventWithId.id, eventWithId)).then(() => {
+      if (this.eventCountInStore !== undefined) {
+        this.eventCountInStore++;
+      }
+    }).catch((e) => {
+      eventWithId.notStored = true;
+      this.logger?.error(e);
+    });
   }
 
   start(): void {
diff --git a/lib/message/log_message.ts b/lib/message/log_message.ts
@@ -60,5 +60,6 @@ export const USER_HAS_NO_FORCED_VARIATION_FOR_EXPERIMENT =
   'No experiment %s mapped to user %s in the forced variation map.';
 export const INVALID_EXPERIMENT_KEY_INFO =
   'Experiment key %s is not in datafile. It is either invalid, paused, or archived.';
+export const EVENT_STORE_FULL = 'Event store is full. Not saving event with id %d.';
 
 export const messages: string[] = [];
