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Fastify SWR

stale-while-revalidate caching and request de-duplication for fastify

Getting Started

Install

npm i @autotelic/fastify-swr

Usage

const fastifySwr = require('@autotelic/fastify-swr')

async function myClient (path, opts = {}) {
  const res = await fetch(new URL(`https://example.com/${path}`), opts)
  return res.json()
}

async function rootPlugin (fastify, opts) {
  await fastify.register(fastifySwr, { handler: myClient, interval: 10 })

  fastify.get('/', async function routeHandler (request, reply) {
    // By default, the handler's name will be used to name the decorator (see API for mor details)
    const content = await fastify.myClient('/endpoint', {
      headers: {
        accept: 'application/json'
      }
    })
    return content
  })
}

Example App

To run the example app clone this repo locally, npm i, and then run the following

npm run dev

Once running, navigate to localhost:3000 in the browser

API

fastifySwr: FastifyPluginAsync<PluginOpts>

PluginOpts

fastifySwr accepts a PluginOpts object with the following properties:

  • handler: (key: string, ...args: any[]) => any - Required. The function to be wrapped by the plugin. The return value of the handler will be cached using a stale-while-revalidate caching strategy. The handler will be called only when the cache is empty or stale. The wrapped handler is accessible as a decorator on the Fastify instance. By default, the handler's name will be used to name the decorator (ie. fastify.myHandler). A custom decorator name can configured using the name option.

  • interval: number - The interval in seconds used to determine when a cache will be deemed stale. Defaults to 60 seconds.

  • name: string - A custom name for the decorator added by this plugin. By default, the name property of the handler will be used.

  • cache: Pick<Map, 'get' | 'set' | 'delete'> - The cache instance for the plugin to use. Must contain get, set, and delete methods matching the signature of a Map. Method names can be changed using the cacheClientMapping option below. Defaults to new Map().

  • cacheClientMapping: { get: string, set: string, delete: string } - An object used to map custom client method names to the default cache method names. For example, if using a Redis client you would pass in { delete: 'del' }.

  • logger: { debug: (log: string) => void } - A logger to be used for the plugin's debug logs. Defaults to fastify.log (Note: the log-level must be set to 'debug' to view the plugin's logs).