@momsfriendlydevco/cache v3.3.7

@momsfriendlydevco/cache

Generic caching component.

This module is a low-level caching component designed to store, retrieve, expire and cleanup a simple key-value storage.

Features:

• Fully ES6 + promise compliant
• Isomorphic back-end (Node) + front-end (Browser) support - just import and use
• Module support for most main caching systems
• Expiry based storage for all setters / getters
• Automatic cleaning
• Function wrapping and memorization support (via cache.worker())
• File contents caching (via cache.fromFile(), Node only)

import Cache from '@momsfriendlydevco/cache';

const storage = new Cache({
	modules: ['memcached', 'mongo', 'memory'], // What modules to try to load (in order of preference)
	// module: 'redis', // Or just specify one
});


// Setup the first available caching system
await storage.init();


// Set something (key, val, [expiry])
storage.set('myKey', 'myValue', '1h').then(setVal => ...)

// Get something (key, [fallback])
storage.get('myKey', 'fallbackValue').then(val => ...)

// Forget something (key)
storage.unset('myKey').then(()=> ...)

// Clean up storage, only supported by some modules
storage.clean().then(()=> ...)

// Hash something, objects also supported
storage.hash(complexObject, val => ...)

All methods return a promise.

Supported Caching Drivers

NOTES:

• By default MemcacheD caches 1mb slabs, see the documentation of the daemon to increase this
• While memory storage is theoretically infinite Node has a memory limit of 1.4gb by default. See the node CLI for details on how to increase this
• Some caching systems (notably MemcacheD) automatically clean entries
• For most modules the storage values are encoded / decoded via marshal. This means that complex JS primitives such as Dates, Sets etc. can be stored without issue. This is disabled in the case of MongoDB by default but can be enabled if needed
• When has() querying is not supported by the module a get() operation will be performed and the result mangled into a boolean instead, this ensures that all modules support has() at the expense of efficiency
• The localstorage module is only only available on the browser release
• The Supabase module by default requires a simple key=>jsonb table setup with a created + expires column. The simplest definition of this would be create table cache (id character varying not null, created_at timestamp with time zone null default now(), expires_at timestamp with time zone null, data jsonb null, constraint cache_pkey primary key (id))

API

Cache(options) (constructor)

Create a new cache handler and populate its default options.

Note that cache.init() needs to be called and needs to complete before this module is usable.

cache.options(Object) or cache.options(key, val)

Set lots of options in the cache handler all at once or set a single key (dotted or array notation are supported).

Valid options are:

NOTES:

• All modules expose their own serialize / deserialize properties which defaults to the main properties by default. These are omitted from the above table for brevity
• The default setup for the serialize property assumes no circular references, override this if you really do need to store them - but at a major performance hit
• The MongoDB module does not serialize or deserialize by default in order to use its own storage format, set the serialize / deserialize properties to the main cache object to enable this behaviour
• filesystem.moveFailTries is necessary because on some systems writing the temporary swap file, setting its expiry then trying to move it over the live file sometimes fails. TO work around this we wait for the filesystem to flush the maximum number of times with a delay in between.

cache.option()

Alias of cache.options().

cache.init()

Initialize the cache handler and attempt to load the modules in preference order. This function is automatically executed in the constructor if cache.settings.init is truthy. This function returns a promise.

cache.autoClean(newInterval)

Setup a time to clean out all expired cache items. If no interval is provided the option autoCleanInterval is used. If the interval is falsy the timer is disabled.

cache.set(Object, expiry) or cache.set(key, value, expiry)

Set a collection of keys or a single key with the optional expiry. The expiry value can be a date, millisecond offset, moment object or any valid timestring string. This function returns a promise.

cache.get(key|keys)

Fetch a single / multiple values. If the value does not exist the fallback value will be provided. If called with an array of keys the result is an object with a key/value combination. This function returns a promise.

cache.unset(key|keys)

Release a single or array of keys. This function returns a promise.

cache.has(key)

Return whether we have the given key but not actually fetch it. NOTE: If the individual module does not implement this a simple get() will be performed and the return mangled into a boolean. See the compatibility tables at the top of this article to see if 'has' is supported. This function returns a promise.

cache.size(key)

Return whether the approximate size in bytes of a cache object. This function returns a promise.

cache.list()

Attempt to return a list of known cache contents. This function returns a promise.

Each item will have at minimum a id and created value. All other values (e.g. expiry) depend on the cache driver being used.

cache.clean()

Attempt to clean up any left over or expired cache entries. This is only supported by some modules. This function returns a promise.

cache.destroy()

Politely close all driver resource handles before shutting down. This function waits for all set operations to complete before resolving. This function returns a promise.

cache.lockAquire(key, expiry)

Request the creation of a unique lock specified by the hashed version of the key (with an optional expiry). This function returns a promise with a boolean indicating if the lock aquire was successful.

cache.lockRelease(key)

Release an aquired lock. This function returns a promise.

cache.lockExists(key)

Query the status of a lock. This function returns a promise with a boolean indicating if the lock exists.

cache.lockSpin(key, options)

Returns a Promise which repeatedly checks if a key exists a given number of times (with configurable retires / backoff). If the key is eventually available, it is created otherwise this function throws.

Options are:

cache.fromFile(key, path, expiry)

Helper function to read a local file into the cache Only available within NodeJS. Since disk files are (kind of) immutable this function works as both a getter (fetch file contents) and a setter (populate into cache) The file's stats are taken into account when reading so that changed files (filesize + date) get hydrated if needed This function returns a promise with the cached files contents.

cache.middleware(expiry, options)

ExpressJS / Connect compatible middleware layer to provide caching middleware. Returns an ExpressJS / Connect middleware function. Only available within NodeJS.

Expiry is optional but if provided as a string is assumed to populate options.expiry.

Options are:

cache.worker(options, worker)

Simple wrapper middleware function which either returns the cached ID or runs a worker to calculate + cache a new one. NOTE: Since Promise execute immediately the worker must be a promise factory

Options can either be a string (assumed as options.id) or an object made up of:

Debugging

This module uses the debug NPM module for debugging. To enable set the environment variable to DEBUG=cache.

For example:

DEBUG=cache node myFile.js