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https://github.com/koajs/cash

HTTP response caching for Koa. Supports Redis, in-memory store, and more!
https://github.com/koajs/cash

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

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# koa-cash

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

Table of Contents

* [koa-cash](#koa-cash)
* [Features](#features)
* [Install](#install)
* [Usage](#usage)
* [API](#api)
* [app.use(koaCash(options))](#appusekoacashoptions)
* [`maxAge`](#maxage)
* [`threshold`](#threshold)
* [`compression`](#compression)
* [`setCachedHeader`](#setcachedheader)
* [`methods`](#methods)
* [`hash()`](#hash)
* [`get()`](#get)
* [`set()`](#set)
* [Example](#example)
* [Max age (optional)](#max-age-optional)
* [CashClear](#cashclear)
* [Notes](#notes)
* [Contributors](#contributors)
* [License](#license)
* [Links](#links)

## 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

:tada: **Pairs great with [@ladjs/koa-cache-responses](https://github.com/ladjs/koa-cache-responses)** :tada:

## Install

[NPM](https://www.npmjs.com/)

```sh
npm install koa-cash
```

[Yarn](https://yarnpkg.com/)

```sh
yarn add koa-cash
```

## Usage

```js
import LRU from 'lru-cache';
import koaCash from 'koa-cash';

// ...
const cache = new LRU();
app.use(koaCash({
get: (key) => {
return cache.get(key);
},
set(key, value) {
return cache.set(key, value);
},
}))

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.

#### `methods`

If an object is passed, then add extra HTTP method caching. This value is empty by default. But `GET` and `HEAD` are enabled.

Eg: `{ POST: true }`

#### `hash()`

A hashing function. By default, it's:

```js
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.

```js
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.

```js
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](https://github.com/isaacs/node-lru-cache), though this would not quite work since it doesn't allow per-key expiration times.

```js
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](https://github.com/ladjs/koa-cache-responses) test folder more examples (e.g. Redis with `ioredis`).

### Max age (optional)

```js
const cached = await ctx.cashed(maxAge) // maxAge is passed to your caching strategy
```

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.

### CashClear

```js
ctx.cashClear('/')
```

This is a special method available on the ctx that you can use to clear the cache for a specific key.

## Notes

* Only `GET` and `HEAD` requests are cached. (Unless overridden)
* 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.

## Contributors

| Name | Website |
| ---------------- | ------------------------- |
| **Jonathan Ong** | |
| **Nick Baugh** | |

## License

[MIT](LICENSE) © [Jonathan Ong](http://jongleberry.com)

## Links

* [NPM](https://www.npmjs.com/)
* [Yarn](https://yarnpkg.com/)