feat(backend): make memory cache sweep interval configurable and clearable (#643)

backend/.env.example

@@ -49,3 +49,9 @@ ADMIN_PUBLIC_KEY=
 # Leave empty to run in single-instance mode (no Redis required).
 REDIS_URL=
 
+# ─── Caching (optional) ───────────────────────────────────────────────────────
+# Time in milliseconds between periodic sweeps to prune expired memory cache
+# entries (default: 60000)
+MEMORY_CACHE_SWEEP_MS=60000
+
+

backend/src/lib/redis.ts

@@ -85,7 +85,39 @@ class MemoryCache {
 }
 
 export const cache = new MemoryCache();
-setInterval(() => cache.cleanup(), 60000);
+
+let sweepInterval: ReturnType<typeof setInterval> | undefined;
+
+/**
+ * Starts the memory cache cleanup sweep interval.
+ * Uses process.env.MEMORY_CACHE_SWEEP_MS (default 60,000ms) unless overridden.
+ */
+export function startMemoryCacheSweep(intervalMs?: number): void {
+  if (sweepInterval) {
+    clearInterval(sweepInterval);
+  }
+
+  const configuredMs = Number.parseInt(
+    process.env.MEMORY_CACHE_SWEEP_MS ?? '60000',
+    10
+  );
+  const ms = intervalMs ?? (Number.isFinite(configuredMs) ? configuredMs : 60000);
+
+  sweepInterval = setInterval(() => cache.cleanup(), ms);
+}
+
+/**
+ * Stops the active memory cache cleanup sweep interval to prevent timer leaks.
+ */
+export function stopMemoryCacheSweep(): void {
+  if (sweepInterval) {
+    clearInterval(sweepInterval);
+    sweepInterval = undefined;
+  }
+}
+
+// Start memory cache sweep automatically on module load
+startMemoryCacheSweep();
 
 // --- Redis Pub/Sub Logic ---
 
@@ -142,6 +174,7 @@ export async function connectRedis(): Promise<void> {
 }
 
 export async function disconnectRedis(): Promise<void> {
+  stopMemoryCacheSweep();
   await Promise.all([_publisher?.quit(), _subscriber?.quit()]);
   _publisher = null;
   _subscriber = null;

backend/tests/redis.test.ts

@@ -1,7 +1,16 @@
-import { describe, it, expect, vi, beforeEach } from 'vitest';
-import { cache, isRedisAvailable } from '../src/lib/redis.js';
+import { describe, it, expect, vi, afterAll } from 'vitest';
+import {
+  cache,
+  isRedisAvailable,
+  startMemoryCacheSweep,
+  stopMemoryCacheSweep,
+} from '../src/lib/redis.js';
 
 describe('Memory Cache', () => {
+  afterAll(() => {
+    stopMemoryCacheSweep();
+  });
+
   it('should set and get values', () => {
     cache.set('key1', 'value1', 10);
     expect(cache.get('key1')).toBe('value1');
@@ -32,6 +41,56 @@ describe('Memory Cache', () => {
   });
 });
 
+describe('Memory Cache Sweep Config', () => {
+  afterAll(() => {
+    stopMemoryCacheSweep();
+  });
+
+  it('should allow starting and stopping sweep interval', () => {
+    vi.useFakeTimers();
+    const cleanupSpy = vi.spyOn(cache, 'cleanup');
+
+    // Stop any existing sweep and start a fresh one with 1000ms interval
+    stopMemoryCacheSweep();
+    startMemoryCacheSweep(1000);
+
+    vi.advanceTimersByTime(2500);
+    expect(cleanupSpy).toHaveBeenCalledTimes(2);
+
+    // Stop sweep and ensure no more calls happen
+    stopMemoryCacheSweep();
+    vi.advanceTimersByTime(2000);
+    expect(cleanupSpy).toHaveBeenCalledTimes(2);
+
+    cleanupSpy.mockRestore();
+    vi.useRealTimers();
+  });
+
+  it('should respect MEMORY_CACHE_SWEEP_MS env variable', () => {
+    vi.useFakeTimers();
+    const cleanupSpy = vi.spyOn(cache, 'cleanup');
+
+    const originalEnv = process.env.MEMORY_CACHE_SWEEP_MS;
+    process.env.MEMORY_CACHE_SWEEP_MS = '500';
+
+    stopMemoryCacheSweep();
+    startMemoryCacheSweep();
+
+    vi.advanceTimersByTime(1200);
+    expect(cleanupSpy).toHaveBeenCalledTimes(2);
+
+    stopMemoryCacheSweep();
+
+    if (originalEnv === undefined) {
+      delete process.env.MEMORY_CACHE_SWEEP_MS;
+    } else {
+      process.env.MEMORY_CACHE_SWEEP_MS = originalEnv;
+    }
+    cleanupSpy.mockRestore();
+    vi.useRealTimers();
+  });
+});
+
 describe('Redis Available', () => {
   it('should return false if redis not initialized', () => {
     expect(isRedisAvailable()).toBe(false);