cacheable - adding in stampede protection via coalesce async

packages/cacheable/README.md

@@ -17,7 +17,7 @@
 * Scalable and trusted storage engine by Keyv
 * Memory Caching with LRU and Expiration `CacheableMemory`
 * Resilient to failures with try/catch and offline
-* Wrap / Memoization for Sync and Async Functions
+* Wrap / Memoization for Sync and Async Functions with Stampede Protection
 * Hooks and Events to extend functionality
 * Shorthand for ttl in milliseconds `(1m = 60000) (1h = 3600000) (1d = 86400000)`
 * Non-blocking operations for layer 2 caching
@@ -310,6 +310,30 @@ const wrappedFunction = cache.wrap(asyncFunction, options);
 console.log(await wrappedFunction(2)); // 4
 console.log(await wrappedFunction(2)); // 4 from cache
 ```
+With `Cacheable` we have also included stampede protection so that a `Promise` based call will only be called once if multiple requests of the same are executed at the same time. Here is an example of how to test for stampede protection:
+
+```javascript
+import { Cacheable } from 'cacheable';
+const asyncFunction = async (value: number) => {
+  return value;
+};
+
+const cache = new Cacheable();
+const options = {
+  ttl: '1h', // 1 hour
+  keyPrefix: 'p1', // key prefix. This is used if you have multiple functions and need to set a unique prefix.
+}
+
+const wrappedFunction = cache.wrap(asyncFunction, options);
+const promises = [];
+for (let i = 0; i < 10; i++) {
+  promises.push(wrappedFunction(i));
+}
+
+const results = await Promise.all(promises); // all results should be the same
+
+console.log(results); // [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+```
 
 In this example we are wrapping an `async` function in a cache with a `ttl` of `1 hour`. This will cache the result of the function for `1 hour` and then expire the value. You can also wrap a `sync` function in a cache:
 

packages/cacheable/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "cacheable",
-	"version": "1.8.3",
+	"version": "1.8.4",
 	"description": "Simple Caching Engine using Keyv",
 	"type": "module",
 	"main": "./dist/index.cjs",
@@ -29,9 +29,9 @@
 	},
 	"devDependencies": {
 		"@keyv/redis": "^3.0.1",
-		"@types/node": "^22.8.4",
+		"@types/node": "^22.9.0",
 		"@vitest/coverage-v8": "^2.1.4",
-		"lru-cache": "^11.0.1",
+		"lru-cache": "^11.0.2",
 		"rimraf": "^6.0.1",
 		"tsup": "^8.3.5",
 		"typescript": "^5.6.3",

packages/cacheable/src/coalesce-async.ts

@@ -0,0 +1,92 @@
+type PromiseCallback<T = any, E = Error> = {
+	resolve: (value: T | PromiseLike<T>) => void;
+	reject: (reason: E) => void;
+};
+
+const callbacks = new Map<string, PromiseCallback[]>();
+
+function hasKey(key: string): boolean {
+	return callbacks.has(key);
+}
+
+function addKey(key: string): void {
+	callbacks.set(key, []);
+}
+
+function removeKey(key: string): void {
+	callbacks.delete(key);
+}
+
+function addCallbackToKey<T>(key: string, callback: PromiseCallback<T>): void {
+	const stash = getCallbacksByKey<T>(key);
+	stash.push(callback);
+	callbacks.set(key, stash);
+}
+
+function getCallbacksByKey<T>(key: string): Array<PromiseCallback<T>> {
+	return callbacks.get(key) ?? [];
+}
+
+async function enqueue<T>(key: string): Promise<T> {
+	return new Promise<T>((resolve, reject) => {
+		const callback: PromiseCallback<T> = {resolve, reject};
+		addCallbackToKey(key, callback);
+	});
+}
+
+function dequeue<T>(key: string): Array<PromiseCallback<T>> {
+	const stash = getCallbacksByKey<T>(key);
+	removeKey(key);
+	return stash;
+}
+
+function coalesce<T>(options: {key: string; error?: Error; result?: T}): void {
+	const {key, error, result} = options;
+
+	for (const callback of dequeue(key)) {
+		if (error) {
+			/* c8 ignore next 3 */
+			callback.reject(error);
+		} else {
+			callback.resolve(result);
+		}
+	}
+}
+
+/**
+ * Enqueue a promise for the group identified by `key`.
+ *
+ * All requests received for the same key while a request for that key
+ * is already being executed will wait. Once the running request settles
+ * then all the waiting requests in the group will settle, too.
+ * This minimizes how many times the function itself runs at the same time.
+ * This function resolves or rejects according to the given function argument.
+ *
+ * @url https://github.com/douglascayers/promise-coalesce
+ */
+export async function coalesceAsync<T>(
+	/**
+   * Any identifier to group requests together.
+   */
+	key: string,
+	/**
+   * The function to run.
+   */
+	fnc: () => T | PromiseLike<T>,
+): Promise<T> {
+	if (!hasKey(key)) {
+		addKey(key);
+		try {
+			const result = await Promise.resolve(fnc());
+			coalesce({key, result});
+			return result;
+		} catch (error: any) {
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+			coalesce({key, error});
+			// eslint-disable-next-line @typescript-eslint/only-throw-error
+			throw error;
+		}
+	}
+
+	return enqueue(key);
+}

packages/cacheable/src/wrap.ts

@@ -1,4 +1,5 @@
 import {hash} from './hash.js';
+import {coalesceAsync} from './coalesce-async.js';
 import {type Cacheable, type CacheableMemory} from './index.js';
 
 export type WrapFunctionOptions = {
@@ -39,15 +40,22 @@ export function wrap<T>(function_: AnyFunction, options: WrapOptions): AnyFuncti
 	const {ttl, keyPrefix, cache} = options;
 
 	return async function (...arguments_: any[]) {
-		const cacheKey = createWrapKey(function_, arguments_, keyPrefix);
-
-		let value = await cache.get(cacheKey) as T | undefined;
-
-		if (value === undefined) {
-			// eslint-disable-next-line @typescript-eslint/no-unsafe-argument
-			value = await function_(...arguments_) as T;
-
-			await cache.set(cacheKey, value, ttl);
+		let value;
+		try {
+			const cacheKey = createWrapKey(function_, arguments_, keyPrefix);
+
+			value = await cache.get(cacheKey) as T | undefined;
+
+			if (value === undefined) {
+				value = await coalesceAsync(cacheKey, async () => {
+					// eslint-disable-next-line @typescript-eslint/no-unsafe-argument
+					const result = await function_(...arguments_) as T;
+					await cache.set(cacheKey, result, ttl);
+					return result;
+				});
+			}
+		} catch {
+			// ignore
 		}
 
 		return value;

packages/cacheable/test/wrap.test.ts

@@ -1,8 +1,8 @@
 /* eslint-disable @typescript-eslint/no-unsafe-assignment */
 import {
-	describe, it, expect,
+	describe, it, expect, vi,
 } from 'vitest';
-import {Cacheable, CacheableMemory} from '../src/index.js';
+import {Cacheable, CacheableMemory, KeyvCacheableMemory} from '../src/index.js';
 import {
 	wrap, createWrapKey, wrapSync, type WrapOptions, type WrapSyncOptions,
 } from '../src/wrap.js';
@@ -162,3 +162,38 @@ describe('wrap function', () => {
 		expect(cacheResult).toBe(undefined);
 	});
 });
+
+describe('wrap function with stampede protection', () => {
+	it('should only execute the wrapped function once when called concurrently with the same key', async () => {
+		const cache = new Cacheable();
+		const mockFunction = vi.fn().mockResolvedValue('result');
+		const mockedKey = createWrapKey(mockFunction, ['arg1'], 'test');
+		const wrappedFunction = wrap(mockFunction, {cache, keyPrefix: 'test'});
+
+		// Call the wrapped function concurrently
+		const [result1, result2, result3, result4] = await Promise.all([wrappedFunction('arg1'), wrappedFunction('arg1'), wrappedFunction('arg2'), wrappedFunction('arg2')]);
+
+		// Verify that the wrapped function was only called two times do to arg1 and arg2
+		expect(mockFunction).toHaveBeenCalledTimes(2);
+
+		// Verify that both calls returned the same result
+		expect(result1).toBe('result');
+		expect(result2).toBe('result');
+		expect(result3).toBe('result');
+
+		// Verify that the result was cached
+		expect(await cache.has(mockedKey)).toBe(true);
+	});
+
+	it('should handle error if the function fails', async () => {
+		const cache = new Cacheable();
+		const mockFunction = vi.fn().mockRejectedValue(new Error('Function failed'));
+		const mockedKey = createWrapKey(mockFunction, ['arg1'], 'test');
+		const wrappedFunction = wrap(mockFunction, {cache, keyPrefix: 'test'});
+
+		await wrappedFunction('arg1');
+
+		// Verify that the wrapped function was only called once
+		expect(mockFunction).toHaveBeenCalledTimes(1);
+	});
+});