node-persistent-cache

This package backs node-cache with a storage engine to persist data across app restarts. It exposes all of node-cache's methods directly. It is backed by node-persist as the default persistence engine, but is easily extensible with any persistent storage engine you might prefer.

Basic Usage

Call node-persistent-cache, setting default options. await new NPC.cache(opts). Enjoy!

const NPC = require('node-persistent-cache');

const cache = await NPC.cache({
	persist: true
});

cache.set('key', 'original value');
cache.get('key'); // 'original value'

// Later . . .
cache.set('key', 'new value');

/* - - - app crashes or is restarted - - - */

const NPC = require('node-persistent-cache');
.
.
.
cache.get('key'); // 'new value'

Configuration

Configuring a New Cache

The configuration is the same as node-cache, with a couple of extras:

• async: (default: false) Control whether the cache is synchronous, exactly like node-cache, or asynchronous. Note:
  • false: Cache is synchronous; the persistence engine attaches listeners to node-cache and updates data whenever set, del, expired, or flush fire.
    • PRO Works just like node-cache; data is restored when the app restarts.
    • CON Data is not persisted asynchronously, so persisted data may not match cached data.
  • true: Cache is asynchronous; methods that update cached data do not return until the persistence engine has stored them.
    • PRO Persisted data guaranteed to be in sync with cached data.
    • CON Behavior does not match node-cache, may require refactoring.
• persist: (default: true) Options passed to persistence engine. If falsy, cache does not persist. If true, use the defaults below.
  • persist.engine: (default: "node-persist") The name of the engine to use to persist data. Engine must have been registered first; see below.
  • persist.prefix: (default: "") Prefix to apply to every key. For example, node-persist prepends prefix to the directory so multiple caches may be used without danger of collision. Not all persistence engines use this feature.
  • persist.opts: (default: {}) Options to pass to the selected persistence engine.

Note that using both persist and useClones: false will cause a warning, as data loaded from a backup cache into node-cache will, by definition, be cloned data.

Configuring Cache Defaults

Just call NPC() to set defaults. The options are exactly like those passed to a new cache.

Storage Engines

By default, node-persistent-cache uses node-persist as the backing persistence engine, but any engine can be registered with the engines object. See engines/base-class for the base class, and see engines/node-persist for the node-persist implementation. Anything that implements the methods in base-class and is newable will work with the storage layer.

Example

const NPC = require('node-persistent-cache');
const engine = function(engineOpts) {
	const self = this;
	.
	.
	.
	return self;
};
NPC.engines.register('my-custom-engine', engine);
const cache = new NPC.cache({
	persist: {
		engine: 'my-custom-engine'
	}
});