koa-cash

HTTP response caching for Koa. Supports Redis, in-memory store, and more!

Table of Contents

• Features
• Install
• Usage
• API
  • app.use(koaCash(options))
  • const cached = await ctx.cashed([maxAge])
• Notes
• Usage
• Contributors
• License

Features

Caches the response based on any arbitrary store you'd like.

• Handles JSON and stream bodies
• Handles gzip compression negotiation (if options.compression is set to true as of v4.0.0)
• Handles 304 responses

🎉 Pairs great with @ladjs/koa-cache-responses 🎉

Install

npm:

npm install koa-cash

yarn:

yarn add koa-cash

Usage

const koaCash = require('koa-cash');

// ...

app.use(koaCash())

app.use(async ctx => {
  // this response is already cashed if `true` is returned,
  // so this middleware will automatically serve this response from cache
  if (await ctx.cashed()) return;

  // set the response body here,
  // and the upstream middleware will automatically cache it
  ctx.body = 'hello world!';
});

API

app.use(koaCash(options))

Options are:

maxAge

Default max age (in milliseconds) for the cache if not set via await ctx.cashed(maxAge).

threshold

Minimum byte size to compress response bodies. Default 1kb.

compression

If a truthy value is passed, then compression will be enabled. This value is false by default.

setCachedHeader

If a truthy value is passed, then X-Cached-Response header will be set as HIT when response is served from the cache. This value is false by default.

hash()

A hashing function. By default, it's:

function hash(ctx) {
 return ctx.response.url; // same as ctx.url
}

ctx is the Koa context and is also passed as an argument. By default, it caches based on the URL.

get()

Get a value from a store. Must return a Promise, which returns the cache's value, if any.

function get(key, maxAge) {
  return Promise;
}

Note that all the maxAge stuff must be handled by you. This module makes no opinion about it.

set()

Set a value to a store. Must return a Promise.

function set(key, value, maxAge) {
  return Promise;
}

Note: maxAge is set by .cash = { maxAge }. If it's not set, then maxAge will be 0, which you should then ignore.

Example

Using a library like lru-cache, though this would not quite work since it doesn't allow per-key expiration times.

const koaCash = require('koa-cash');
const LRU = require('lru-cache');

const cache = new LRU({
  maxAge: 30000 // global max age
})

app.use(koaCash({
  get (key, maxAge) {
    return cache.get(key)
  },
  set (key, value) {
    cache.set(key, value)
  }
}))

See @ladjs/koa-cache-responses test folder more examples (e.g. Redis with ioredis).

const cached = await ctx.cashed([maxAge])

This is how you enable a route to be cached. If you don't call await ctx.cashed(), then this route will not be cached nor will it attempt to serve the request from the cache.

maxAge is the max age passed to get().

If cached is true, then the current request has been served from cache and you should early return. Otherwise, continue setting ctx.body= and this will cache the response.

Notes

• Only GET and HEAD requests are cached.
• Only 200 responses are cached. Don't set 304 status codes on these routes - this middleware will handle it for you
• The underlying store should be able to handle Date objects as well as Buffer objects. Otherwise, you may have to serialize/deserialize yourself.

Usage

Contributors

License

MIT © Jonathan Ong