@ardrive/ardrive-promise-cache

@ardrive/ardrive-promise-cache is a caching library designed to cache promises, enabling faster subsequent retrievals of data. It includes two types of caching implementations:

• PromiseCache - a simple cache that stores promises in memory
• ReadThroughPromiseCache - a wrapper of PromiseCache that allows providing an async readThroughFunction that is called when the cache does contain the requested key

Installation

You can install the library using npm or yarn:

npm i @ardrive/ardrive-promise-cache

yarn add @ardrive/ardrive-promise-cache

Usage

PromiseCache

Example

import { PromiseCache, CacheParams } from '@ardrive/ardrive-promise-cache';

const params: CacheParams = {
  cacheCapacity: 100,
  cacheTTL: 60_000, // cache for 1 minute
};

const cache = new PromiseCache<string, number>(params);

// Storing a promise
const promise1 = new Promise<number>((resolve) => resolve(42));

cache.put('answer', promise1);

// resolves to 42
await cache.get('answer');

const promise2 = new Promise<number>((resolve) => resolve(100));

// overwrite existing cached promise
cache.put('answer', promise2);

// resolves to 100
await cache.get('answer');

// removes the promise from the cache
cache.remove('answer');

// resolves to undefined as no longer exists in the cache
await cache.get('answer');

// clear the cache
cache.clear();

// Getting the cache size
const size = cache.size();

API

constructor({ cacheCapacity, cacheTTL }: CacheParams)

Creates a new PromiseCache instance with the specified capacity and time-to-live (TTL) for cached items.

put(key: K, value: Promise<V>): Promise<V>

Stores a promise with the specified key in the cache.

get(key: K): Promise<V> | undefined

Retrieves a promise from the cache using the specified key. Returns undefined if the key is not found.

remove(key: K): void

Removes a promise from the cache using the specified key.

clear(): void

Clears the entire cache.

size(): number

Returns the current number of items in the cache.

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ReadThroughPromiseCache

A Read Through Cache is useful for high throughput systems. If the cache contains the requested data, it is immediately returned. If the data does not exist (or has expired), the cache will fetch and place resulting promise in the cache for future requests. Some examples and use cases for Read Through Caching (and other caching patterns) can be found here.

Example

import { ReadThroughPromiseCache, CacheParams } from '@ardrive/ardrive-promise-cache';

const params: CacheParams = {
  cacheCapacity: 100,
  cacheTTL: 60_000, // cache for 1 minute
};

const readThroughCacheParams: ReadThroughPromiseCacheParams<string,AxiosResponse> = {
  cacheParams: params,
  readThroughFunction: async (key: K) => {
    // This function will be called when the cache does not contain the requested key.
    // It should return a promise that resolves with the value to cache.
    return axios.get(`https://example.com/api/${key}`);
  }
};

// create ReadThroughPromiseCache with capacity of 100 and TTL of 1 minute, and readThroughFunction to call API function
const readThroughCache = new ReadThroughPromiseCache<string, AxiosResponse>(readThroughCacheParams);

// caches new key and resulting axios promise (https://example.com/api/example) for 1 minute
const { status, data } = await readThroughCache.get('example')

// the cached axios promise will be returned
const { status: cachedStatus, data: cacheData } = await readThroughCache.get('example')

// wait 1 minute
await new Promise((res) => setTimeout(() => res, 60_000);

// 'example' key has expired, so readThroughFunction will be called again and new promise will be returned
const { status: refreshedStatus, data:refreshedData } = await readThroughCache.get('example')

API

constructor({ cacheParams: { cacheCapacity, cacheTTL }, readThroughFunction: (key: string) => Promise<V>: ReadThroughPromiseCacheParams)

Creates a new ReadThroughPromiseCache instance with the specified capacity and time-to-live (TTL) for cached items and readThroughFunction that will be called when the cache does not contain the key.

getWithStatus(key: K): Promise<{status: 'hit' | 'miss', data: V}>

Returns a Promise'd object, with the key 'data' pre-awaited and 'status' key indicating if it was a hit or a miss.

Note

The method cacheKeyString(key: K): string is used internally to create cache keys. The default implementation may not sufficiently differentiate keys for certain object types, depending on their toJSON implementation. You may need to override this method if you encounter issues.