RICORDO

Micro caching / memo library with ttl support.

When you need some caching, and setting up Redis is too much. Ricordo is a 700 bytes library that fully supports Node.js and the browser. With time-to-live support and full control on the number of cached keys.

Table of Contents

• Installation
• Usage
  • Caching a function
  • Expesive functions
  • Using TTL (time-to-live)
  • Setting limits on number of cached keys
  • Destroy cache
  • Force deletion
  • Caching React component
• API
  • Ricordo
  • Config
  • Destroy
• License

Installation

If using npm:

npm install ricordo

If not:

<script src="https://unpkg.com/ricordo/dist/ricordo.umd.js"></script>

Usage

Ricordo usage is pretty straightforward:

1. Create a new Ricordo instance passing a function to cache and some optional arguments.
2. Use the function.

Caching a function

const Ricordo = require('ricordo'); // Node.js

const demoFunc = a => `hello ${a}`;

// Cache function
const cached = new Ricordo(demoFunc);

// Use function
cached('world'); // No cache hit.
cached('world'); // cache hit.

Expesive functions

const Ricordo = require('ricordo'); // Node.js

const fibonacci = n => (n < 2) ? n : fibonacci(n - 1) + fibonacci(n - 2);

// Cache function
const cached = new Ricordo(fibonacci);

// First execution
cached(40); // 1200ms

// Cached execution
cached(40); // 0ms
cached(40); // 0ms
cached(40); // 0ms

Using TTL (time-to-live)

Ricordo supports a time-to-live prop on a newly created instance. ttl define (in ms) the lifespan of the cached key. The key will be removed from cache after ttl if there are no hits to that key.

NOTE: ttl must be above 1000ms.

const Ricordo = require('ricordo'); // Node.js

// Cache function
const cached = new Ricordo(a => `hello ${a}`, {
  ttl: 5000 * 1000, // lifespan of key.
});

// ####### 1 #######
// First execution
cached('world'); // no cache hit => insertion.

// Executing function after ttl
setTimeout(() => cached('world'), 5000 * 1001); // No cache hit => New insertion

// ####### 2 #######
// First execution
cached('world'); // no cache hit => insertion.
cached('world'); // cache hit => ttl will be renewed.

// Executing function after ttl
setTimeout(() => cached('world'), 5000 * 1001); // cache hit!!! 🎉

Setting limits on number of cached keys

You can set a limit on the number of keys that can be cached. When limit n of inserted keys is hit, the cache will return to ideal n of items. The keys that are kept when limit is hit are the ideal n of items most accessed in the ttl iterval.

NOTE: A range is used so the operations of sorting and deleting the useless keys will be less frequent.

const Ricordo = require('ricordo'); // Node.js

// Cache function
const cached = new Ricordo(a => `hello ${a}`, {
  ttl: 5000 * 1000, // lifespan of key.
  ideal: 2, // Ideal number of cached keys
  limit: 4, // Max number of cached keys
});

cached('A'); // No cache
cached('B'); // No cache
cached('C'); // No cache

// Accessing keys A, B for 5 times.
[1, 2, 3, 4, 5].forEach(e => {
  cached('A'); // From cache
  cached('B'); // From cache
});

// Accessing C key for 2 times.
[1, 2].forEach(e => {
  cached('C'); // From cache
});

// On the next insertion the `limit` (4) is hit
// => Only the `ideal` (2) items that are most accessed will be kept. => (A, B)
cached('D') // New insertion

// Then...
cached('A') // From cache
cached('B') // From cache
cached('C') // No cache

Destroy cache

Every ricordo instance has a destroy method. This method will clear every cached key.

const Ricordo = require('ricordo'); // Node.js

// Cache function
const cached = new Ricordo(a => `hello ${a}`);

cached('A'); // No cache
cached('B'); // No cache

cached('A'); // From cache
cached('B'); // From cache

// Destroy every cached key.
cache.destroy();

cached('A'); // No cache
cached('B'); // No cache

Force deletion

If force flag is enabled, cached keys will be deleted after ttl. Also if there are multiple hits to that key.

const Ricordo = require('ricordo'); // Node.js

// Specifying force flag.
const cached = new Ricordo(a => `hello ${a}`, { ttl: 1000, force: true });

cached('A'); // No cache
cached('A'); // From cache
cached('A'); // From cache

setTimeout(() => cached('A'), 1001) // No cache => lifespan not renewed.

Caching React component

import React, { Component } from 'react';
import Ricordo from 'ricordo';

const C = a => <h1>hello {a}</h1>;

const cached = new Ricordo(C);

class App extends Component {

  // Invoking cached function => now 'world' is a registered key
  // The next time that the function will be computed with 'world' as argument,
  // the previously created component will be returned.
  render = () => <div>{cached('world')}</div>;
}

API

Ricordo

| param | type | required | default | spec | | ------ | -------- | -------- | --------- | ----------------------- | | func | function | yes | | Function to cache. | | config | object | no | undefined | Defines cache behavior. |

Config

| param | type | required | default | spec | | ----- | --------------- | ---------------------------------- | --------- | --------------------------------------------------- | | ttl | number [> 1000] | no | undefined | Lifespan of cached key | | ideal | number | no [yes, if limit is specified] | undefined | Ideal number of cached keys | | limit | number | no [yes, if ideal is specified] | undefined | Max number of cached keys | | force | boolean | no | false | If set to true, cache will not be renewed after ttl |

Destroy

| param | type | required | default | spec | |-------|---------|------------------------------------|-----------|------------------------------------------------------------------------------| | key | any | no | undefined | key to delete from cache. If no key is specified, every key will be deleted. |

License

MIT.