with-simple-cache

with-simple-cache

A wrapper that makes it simple to add cache to any function.

Notable features:

• Wrapper pattern for simple and clean usage
• Automatic cache key definition
• Customizable cache data store

Install

npm install --save with-simple-cache

Quick start

Synchronous Cache, Synchronous Logic

in order prevent redundant sync computations from one machine, you can use a synchronous cache

for example:

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const solveSuperToughMathProblem = withSimpleCache(
  ({ a, b }) => ({ solution: a + b }),
  { cache: createCache() },
);
const result1 = solveSuperToughMathProblem({ a: 1, b: 1 }); // runs the logic, sticks the output into the cache, returns a reference to that output
const result2 = solveSuperToughMathProblem({ a: 1, b: 1 }); // finds the output in the cache, returns a reference to that output
expect(result1).toBe(result2); // same exact object, identified by same reference

Synchronous Cache, Asynchronous Logic

in order to prevent duplicate async requests from one machine, you can use a synchronous cache

for example:

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getApiResult = withSimpleCache(
  async ({ name, number }) => axios.get(URL, { name, number }),
  { cache: createCache() },
);
const result1 = getApiResult({ name: 'casey', number: 821 }); // calls the api, puts promise of results into cache, returns that promise
const result2 = getApiResult({ name: 'casey', number: 821 }); // returns the same promise from above, because it was found in cache - since same input as request above was used
expect(result1).toBe(result2); // same exact object - the promise
expect(await result1).toBe(await result2); // same exact object - the result of the promise

Asynchronous Cache, Asynchronous Logic

in order to cache the output of async logic in a persistant store or across machines, you'll likely find you need to use an async cache.

for example

import { createCache as createOnDiskCache } from 'simple-on-disk-cache';
import { withSimpleCacheAsync } from 'with-simple-cache';

const getApiResult = withSimpleCacheAsync(
  async ({ name, number }) => axios.get(URL, { name, number }),
  { cache: createOnDiskCache() },
);
const result1 = getApiResult({ name: 'casey', number: 821 }); // calls the api, puts promise of results into cache, returns that promise
const result2 = getApiResult({ name: 'casey', number: 821 }); // returns the same promise from above, because it was found in cache - since same input as request above was used
expect(result1).toBe(result2); // same exact object - the promise
expect(await result1).toBe(await result2); // same exact object - the result of the promise

note: this wrapper additionally uses an in-memory cache internally to cache the promise the async cache returns, to prevent duplicate requests

Examples

Add cache to an existing function

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getRecipesFromApiWithCache = withSimpleCache(getRecipesFromApi, { cache: createCache() });

Define the function with cache directly

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getBookByName = withSimpleCache(
  async (name: string) => {
    /* ... get the book ... */
    return book;
  },
  {
    cache: createCache(),
  },
);

Use a custom persistance layer

local storage, for example:

import { withSimpleCache } from 'with-simple-cache';

const getRecipesFromApiWithLocalStorageCache = withSimpleCache(getRecipesFromApi, {
  // just define how a cache can `get` from and `set` to this data store
  cache: {
    get: (key) => localStorage.getItem(key),
    set: (key, value) => localStorage.setItem(key, value),
  },
});

Use an asynchronous persistance layer

some extra logic is required in order to work with asynchronous caches. therefore, a different wrapper is available for this usecase: withSimpleCacheAsync.

asynchronous cache on-disk, for example:

import { createCache } from 'simple-on-disk-cache';
import { withSimpleCacheAsync } from 'with-simple-cache';

const getRecipesFromApiWithAsyncCache = withSimpleCacheAsync(getRecipesFromApi, {
  cache: createCache({ directory: { s3: { bucket: '__bucket__', prefix: '__prefix__' } } }),
});

Use a custom key serialization method

serialize the key as the sha hash of the args, for example

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getRecipesFromApiWithLocalStorageCache = withSimpleCache(getRecipesFromApi, {
  cache: createCache(),
  serialize: {
    key: (args) =>
        crypto.createHash('sha256').update(JSON.stringify(args)).digest('hex'),
  }
});

Use a custom value serialization and deserialization method

if your cache requires you to store data as a string, as is typically the case with asynchronous caches, you can define how to serialize and deserialize the response of your logic

import { createCache } from 'simple-on-disk-cache';
import { withSimpleCacheAsync } from 'with-simple-cache';

const getRecipesFromApiWithLocalStorageCache = withSimpleCacheAsync(getRecipesFromApi, {
  cache: createCache({ directory: { s3: { bucket: '__bucket__', prefix: '__prefix__' } } }),
  serialize: {
    value: async (response) => JSON.stringify(await response),
  },
  deserialize: {
    value: async (cached) => JSON.parse(await cached)
  }
});

Define the cache at runtime from function inputs

if your cache is defined as part of the inputs to your function (e.g., if you're using the input context pattern), you define where to find the cache in the inputs

for example

import { createCache, SimpleInMemoryCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getBookByName = withSimpleCache(
  async ({ name: string}, context: { cache: SimpleInMemoryCache<Book> }) => {
    /* ... get the book ... */
    return book;
  },
  {
    cache: ({ fromInput }) => fromInput[1].context.cache, // grab the cache from the input's "context" parameter (the second input parameter)
  },
);

const book = await getBookByName({ name: 'Hitchhikers Guide to the Galaxy' }, { cache: createCache() });

Features

Automatic cache key

The arguments your function is invoked with is used as the cache key, after serialization. For example:

import { createCache } from 'simple-in-memory-cache';
import { withSimpleCache } from 'with-simple-cache';

const getZodiacSign = withSimpleCache(async ({ birthday }: { birthday: string }) => /* ... */, { cache: createCache() });

getZodiacSign({ birthday: '2020-07-21' }); // here the cache key is `[{"birthday":"2020-07-21"}]`

note: array order does matter

Customizable cache data store

You can easily use a custom cache or custom data store / persistance layer with this wrapper.

import { withSimpleCache } from 'with-simple-cache';

const getZodiacSign = withSimpleCache(
  async ({ birthday }: { birthday: string }) => /* ... */,
  {
    cache: {
      get: (key: string) => /* ... how to get from your custom data store ... */,
      set: (key: string, value: any) => /** ... how to set to your custom data store ... */,
    }
  }
);