keyv/README.md

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	<img width="250" src="https://rawgit.com/lukechilds/keyv/master/media/logo.svg" alt="keyv">
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> Simple key-value storage with support for multiple backends

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Keyv provides a consistent interface for key-value storage across multiple backends via storage adapters. Supports TTL based expiry making it suitable as a cache or a persistent key-value store.

## Features

There are a few existing modules similar to Keyv, however none of them fulfilled all of my requirements. I created Keyv because I wanted something that:

- Wasn't bloated
- Had a simple Promise based API
- Suitable as a TTL based cache or persistent key-value store
- [Easily embeddable](#add-cache-support-to-your-module) inside another module
- Works with any storage that implements the [`Map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) API
- Handles all JavaScript types (values can be `Buffer`/`null`/`undefined`)
- Supports namespaces
- Wide range of [**efficient, well tested**](#official-storage-adapters) storage adapters
- Connection errors are passed through (db failures won't kill your app)
- Supports the current active LTS version of Node.js or higher

## Usage

Install Keyv.

```
npm install --save keyv
```

By default everything is stored in memory, you can optionally also install a storage adapter.

```
npm install --save keyv-redis
npm install --save keyv-mongo
npm install --save keyv-sqlite
npm install --save keyv-postgres
npm install --save keyv-mysql
```

Create a new Keyv instance, passing your connection string if applicable. Keyv will automatically load the correct storage adapter.

```js
const Keyv = require('keyv');

// One of the following
const keyv = new Keyv();
const keyv = new Keyv('redis://user:pass@localhost:6379');
const keyv = new Keyv('mongodb://user:pass@localhost:27017/dbname');
const keyv = new Keyv('sqlite://path/to/database.sqlite');
const keyv = new Keyv('postgresql://user:pass@localhost:5432/dbname');
const keyv = new Keyv('mysql://user:pass@localhost:3306/dbname');

// Handle DB connection errors
keyv.on('error' err => console.log('Connection Error', err));

await keyv.set('foo', 'expires in 1 second', 1000); // true
await keyv.set('foo', 'never expires'); // true
await keyv.get('foo'); // 'never expires'
await keyv.delete('foo'); // true
await keyv.clear(); // undefined
```

### Namespaces

You can namespace your Keyv instance to avoid key collisions and allow you to clear only a certain namespace while using the same database.

```js
const users = new Keyv('redis://user:pass@localhost:6379', { namespace: 'users' });
const cache = new Keyv('redis://user:pass@localhost:6379', { namespace: 'cache' });

await users.set('foo', 'users'); // true
await cache.set('foo', 'cache'); // true
await users.get('foo'); // 'users'
await cache.get('foo'); // 'cache'
await users.clear(); // undefined
await users.get('foo'); // undefined
await cache.get('foo'); // 'cache'
```

## Official Storage Adapters

The official storage adapters are covered by over 150 integration tests to guarantee consistent behaviour. They are lightweight, efficient wrappers over the DB clients making use of indexes and native TTLs where available.

Database | Adapter | Native TTL | Status
---|---|---|---
Redis | [keyv-redis](https://github.com/lukechilds/keyv-redis) | Yes | [![Build Status](https://travis-ci.org/lukechilds/keyv-redis.svg?branch=master)](https://travis-ci.org/lukechilds/keyv-redis)
MongoDB | [keyv-mongo](https://github.com/lukechilds/keyv-mongo) | Yes | [![Build Status](https://travis-ci.org/lukechilds/keyv-mongo.svg?branch=master)](https://travis-ci.org/lukechilds/keyv-mongo)
SQLite | [keyv-sqlite](https://github.com/lukechilds/keyv-sqlite) | No | [![Build Status](https://travis-ci.org/lukechilds/keyv-sqlite.svg?branch=master)](https://travis-ci.org/lukechilds/keyv-sqlite)
PostgreSQL | [keyv-postgres](https://github.com/lukechilds/keyv-postgres) | No | [![Build Status](https://travis-ci.org/lukechilds/keyv-postgres.svg?branch=master)](https://travis-ci.org/lukechildskeyv-postgreskeyv)
MySQL | [keyv-mysql](https://github.com/lukechilds/keyv-mysql) | No | [![Build Status](https://travis-ci.org/lukechilds/keyv-mysql.svg?branch=master)](https://travis-ci.org/lukechilds/keyv-mysql)

## Third-party Storage Adapters

You can also use third-party storage adapters or build your own. Keyv will wrap these storage adapters in TTL functionality and handle complex types internally.

```js
const Keyv = require('keyv');
const myAdapter = require('./my-storage-adapter');

const keyv = new Keyv({ store: myAdapter });
```

Any store that follows the [`Map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) api will work.

```js
new Keyv({ store: new Map() });
```

For example, [`quick-lru`](https://github.com/sindresorhus/quick-lru) is a completely unrelated module that implements the Map API.

```js
const Keyv = require('keyv');
const QuickLRU = require('quick-lru');

const lru = new QuickLRU({ maxSize: 1000 });
const keyv = new Keyv({ store: lru });
```

## Add Cache Support to your Module

Keyv is designed to be easily embedded into other modules to add cache support. The recommended pattern is to expose a `cache` option in your modules options which is passed through to Keyv. Caching will work in memory by default and users have the option to also install a Keyv storage adapter and pass in a connection string.

You should also set a namespace for your module so you can safely call `.clear()` without clearing unrelated app data.

Inside your module:

```js
class AwesomeModule {
	constructor(opts) {
		this.cache = new Keyv(opts.cache, { namespace: 'awesome-module' });
	}
}
```

Now it can be consumed like this:

```js
const AwesomeModule = require('awesome-module');

// Caches stuff in memory by default
const awesomeModule = new AwesomeModule();

// After npm install --save keyv-redis
const awesomeModule = new AwesomeModule({ cache: 'redis://localhost' });
```

## API

### new Keyv([uri], [options])

Returns a new Keyv instance.

The Keyv instance is also an `EventEmitter` that will emit an `'error'` event if the storage adapter connection fails.

### uri

Type: `String`<br>
Default: `undefined`

The connection string URI.

Merged into the options object as options.uri.

### options

Type: `Object`

The options object is also passed through to the storage adapter. Check your storage adapter docs for any extra options.

#### options.namespace

Type: `String`<br>
Default: `'keyv'`

Namespace for the current instance.

#### options.ttl

Type: `Number`<br>
Default: `undefined`

Default TTL. Can be overridden by specififying a TTL on `.set()`.

#### options.store

Type: `Storage adapter instance`<br>
Default: `new Map()`

The storage adapter instance to be used by Keyv.

#### options.adapter

Type: `String`<br>
Default: `undefined`

Specify an adapter to use. e.g `'redis'` or `'mongodb'`.

### Instance

Keys must always be strings. Values can be of any type.

#### .set(key, value, [ttl])

Set a value.

By default keys are persistent. You can set an expiry TTL in milliseconds.

Returns `true`.

#### .get(key)

Returns the value.

#### .delete(key)

Deletes an entry.

Returns `true` if the key existed, `false` if not.

#### .clear()

Delete all entries in the current namespace.

Returns `undefined`.

## License

MIT © Luke Childs