polycache

Flexible multi cache module

A cache module for node that allows easy wrapping of functions, tiered caches, and a consistent interface.

Features

• Made with Typescript and compatible with ESModules
• Easy way to wrap any function in cache.
• Tiered caches -- data gets stored in each cache and fetched from the highest priority cache(s) first.
• Use any cache you want, as long as it has the same API.
• 100% test coverage via vitest.

Installation

npm install polycache-core

Usage Examples

Single Store

import { caching, createLruStore } from 'polycache-core';

const memoryCache = caching(
  createLruStore({
    max: 100,
    ttl: 10 * 1000 /*milliseconds*/,
  }),
);

const ttl = 5 * 1000; /*milliseconds*/
await memoryCache.set('foo', 'bar', ttl);

console.log(await memoryCache.get('foo'));
// >> "bar"

await memoryCache.del('foo');

console.log(await memoryCache.get('foo'));
// >> undefined

const getUser = (id: string) => new Promise.resolve({ id: id, name: 'Bob' });

const userId = 123;
const key = 'user_' + userId;

console.log(await memoryCache.wrap(key, () => getUser(userId), ttl));
// >> { id: 123, name: 'Bob' }

Example setting/getting several keys with setMany() and getMany()

await memoryCache.store.setMany(
  [
    ['foo', 'bar'],
    ['foo2', 'bar2'],
  ],
  ttl,
);

console.log(await memoryCache.store.getMany('foo', 'foo2'));
// >> ['bar', 'bar2']

// Delete keys with delMany() passing arguments...
await memoryCache.store.delMany('foo', 'foo2');

Custom Stores

Custom stores can be easily built by adhering to the Store type.

Multi-Store

import { multiCaching } from 'polycache-core';

const multiCache = multiCaching([memoryCache, someOtherCache]);
const userId2 = 456;
const key2 = 'user_' + userId;
const ttl = 5;

// Sets in all caches.
await multiCache.set('foo2', 'bar2', ttl);

// Fetches from highest priority cache that has the key.
console.log(await multiCache.get('foo2'));
// >> "bar2"

// Delete from all caches
await multiCache.del('foo2');

// Sets multiple keys in all caches.
// You can pass as many key, value tuples as you want
await multiCache.setMany(
  [
    ['foo', 'bar'],
    ['foo2', 'bar2'],
  ],
  ttl,
);

// getMany() fetches from highest priority cache.
// If the first cache does not return all the keys,
// the next cache is fetched with the keys that were not found.
// This is done recursively until either:
// - all have been found
// - all caches has been fetched
console.log(await multiCache.getMany('key', 'key2'));
// >> ['bar', 'bar2']

// Delete keys with delMany() passing arguments...
await multiCache.delMany('foo', 'foo2');

Refresh cache keys in background

Both the caching and multicaching modules support a mechanism to refresh expiring cache keys in background when using the wrap function.
This is done by adding a refreshThreshold attribute while creating the caching store.

If refreshThreshold is set and after retrieving a value from cache the TTL will be checked.
If the remaining TTL is less than refreshThreshold, the system will update the value asynchronously,
following same rules as standard fetching. In the meantime, the system will return the old value until expiration.

NOTES:

• In case of multicaching, the store that will be checked for refresh is the one where the key will be found first (highest priority).
• If the threshold is low and the worker function is slow, the key may expire and you may encounter a racing condition with updating values.
• The background refresh mechanism currently does not support providing multiple keys to wrap function.
• If no ttl is set for the key, the refresh mechanism will not be triggered. For redis, the ttl is set to -1 by default.

For example, pass the refreshThreshold to caching like this:

import { createLruStore, caching } from 'polycache-core';

const memoryCache = caching(
  createLruStore({
    max: 100,
    ttl: 10 * 1000 /*milliseconds*/,
  }),
  {
    refreshThreshold: 3 * 1000 /*milliseconds*/,
  },
);

When a value will be retrieved from Redis with a TTL minor than 3sec, the value will be updated in the background.

Store Engines

• Built-in LRU store for in-memory caching.

Under construction...

Contribute

If you would like to contribute to the project, please fork it and send us a pull request. Please add tests for any new features or bug fixes.

License

polycache is licensed under the MIT license.