Middy cache middleware

This middleware offers a simple but flexible caching layer that allows to cache the response associated to a given event and return it directly (without running the handler) if the same event is received again in a successive execution.

By default, the middleware stores the cache in memory, so the persistence is guaranteed only for a short amount of time (the duration of the container), but you can use the configuration layer to provide your own caching implementation.

Install

To install this middleware you can use NPM:

npm install --save @middy/cache

Options

• calculateCacheId (function) (optional): a function that accepts the event object as a parameter and returns a promise that resolves to a string which is the cache id for the give request. By default the cache id is calculated as md5(JSON.stringify(event)).
• getValue (function) (optional): a function that defines how to retrieve the value associated to a given cache id from the cache storage. It accepts key (a string) and returns a promise that resolves to the cached response (if any) or to undefined (if the given key does not exists in the cache)
• setValue (function) (optional): a function that defines how to set a value in the cache. It accepts a key (string) and a value (response object). It must return a promise that resolves when the value has been stored.

Sample usage

const middy = require('@middy/core')
const cache = require('@middy/cache')

// assumes the event contains a unique event identifier
const calculateCacheId = (event) => Promise.resolve(event.id)
// use in-memory storage as example
const myStorage = {}
// simulates a delay in retrieving the value from the caching storage
const getValue = (key) => new Promise((resolve, reject) => {
  setTimeout(() => resolve(myStorage[key]), 100)
})
// simulates a delay in writing the value in the caching storage
const setValue = (key, value) => new Promise((resolve, reject) => {
  setTimeout(() => {
    myStorage[key] = value
    return resolve()
  }, 100)
})

const originalHandler = (event, context, cb) => {
  /* ... */
}

const handler = middy(originalHandler)
  .use(cache({
    calculateCacheId,
    getValue,
    setValue
  }))

Middy documentation and examples

For more documentation and examples, refers to the main Middy monorepo on GitHub or Middy official website.

Contributing

Everyone is very welcome to contribute to this repository. Feel free to raise issues or to submit Pull Requests.

License

Licensed under MIT License. Copyright (c) 2017-2018 Luciano Mammino and the Middy team.