memcache-client-memoizer

memcache-client-memoizer

A function memoizer using a get/set cache client.

Install:

npm i memcache-client-memoizer

API

memoizer(options)

Arguments

• options: object. Required. An object with the following keys:
  • client: { get: (anything) => Promise, set: (anything, value, options) }. A cache client instance, must have a get and set method. The get method must return a promise.
  • clientProviderFn: () => client A function which returns a client (defined above); (Either a client or clientProviderFn must be passed.)
  • fn: Function. Required. The function to memoize, must return a Promise.
  • keyFn: (args to fn) => anything. Required. A function which returns a cache-key (can be anything) for caching. This function is called with the same arguments as fn, allowing you to create a dynamic cache-key, for example:

    const exampleKeyFn = ({ name, color }) => `${name}:${color}` // can be anything
    

  • setOptions: anything. Optional. For memcached-client this can be command options.
  • cacheResultTransformFn. (result-from-cache) => transformed-result. Function to transform cache-result, defaults to (x) => x. This is useful if your cache service sends along the value in a different form than is returned by your fn.
  • skipCacheFn: (args to fn) => Boolean. Optional. A function which indicates that the call to fn should skip the cache.

Note:

Rejected promises are not memoized - since that's probably not what you want :)

memcache-client example:

const MemcacheClient = require('memcache-client')
const { memoizer } = require('memcache-client-memoizer')

const fnToMemoize = ({ name, color }) => Promise.resolve({ name, color })

const memoizedFn = memoizer({
  clientProviderFn: () => new MemcacheClient({ server: 'localhost:11211' }),
  fn: fnToMemoize,
  keyFn: ({ name, color }) => `${name}:${color}`, // this can return anything
  cacheResultTransformFn: ({value}) => value,
  skipCacheFn: ({ name, color }) => false,
})

memoizedFn({name: 'Max', color: 'blue'})
  .then((result) => { ... })  // cache miss, fill cache, returns {name: 'Max', color: 'blue'}

// later on...
memoizedFn({name: 'Max', color: 'blue'})
  .then((result) => { ... })  // cache hit, returns {name: 'Max', color: 'blue'}

catbox example:

const Catbox = require('catbox');
const Memory = require('catbox-memory');

const cacheTtlMilliseconds = 1000 * 60 * 5; // 5 min
const client = new Catbox.Client(Memory);
await client.start();

const fnToMemoize = ({ name, color }) => Promise.resolve({ name, color })

const memoizedFn = memoizer({
  client,
  fn: fnToMemoize,
  keyFn: ({ name, color }) => ({ segment: 'test', id: 'test-cache' }), // this can return anything
  setOptions: cacheTtlMilliseconds,
  cacheResultTransformFn: ({ item }) => item,
  skipCacheFn: ({ name, color }) => false,
})

memoizedFn({name: 'Max', color: 'blue'})
  .then((result) => { ... })  // cache miss, fill cache, returns {name: 'Max', color: 'blue'}

// later on...
memoizedFn({name: 'Max', color: 'blue'})
  .then((result) => { ... })  // cache hit, returns {name: 'Max', color: 'blue'}