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> Simple key-value storage with support for multiple backends
[](https://travis-ci.org/lukechilds/keyv)
[](https://coveralls.io/github/lukechilds/keyv?branch=master)
[](https://www.npmjs.com/package/keyv)
[](https://www.npmjs.com/package/keyv)
Keyv provides a consistent interface for key-value storage across multiple backends via storage adapters. It 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 Keyv is different because it:
- Isn't bloated
- Has 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 JSON types plus `Buffer`
- 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'
```
### Custom Serializers
Keyv uses [`json-buffer`](https://github.com/dominictarr/json-buffer) for data serialization to ensure consistency across different backends.
You can optionally provide your own serialization functions to support extra data types or to serialize to something other than JSON.
```js
const keyv = new Keyv({ serialize: JSON.stringify, deserialize: JSON.parse });
```
**Warning:** Using custom serializers means you lose any guarantee of data consistency. You should do extensive testing with your serialisation functions and chosen storage engine.
## Official Storage Adapters
The official storage adapters are covered by [over 150 integration tests](https://travis-ci.org/lukechilds/keyv/jobs/260418145) 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 | [](https://travis-ci.org/lukechilds/keyv-redis) [](https://coveralls.io/github/lukechilds/keyv-redis?branch=master)
MongoDB | [@keyv/mongo](https://github.com/lukechilds/keyv-mongo) | Yes | [](https://travis-ci.org/lukechilds/keyv-mongo) [](https://coveralls.io/github/lukechilds/keyv-mongo?branch=master)
SQLite | [@keyv/sqlite](https://github.com/lukechilds/keyv-sqlite) | No | [](https://travis-ci.org/lukechilds/keyv-sqlite) [](https://coveralls.io/github/lukechilds/keyv-sqlite?branch=master)
PostgreSQL | [@keyv/postgres](https://github.com/lukechilds/keyv-postgres) | No | [](https://travis-ci.org/lukechildskeyv-postgreskeyv) [](https://coveralls.io/github/lukechilds/keyv-postgres?branch=master)
MySQL | [@keyv/mysql](https://github.com/lukechilds/keyv-mysql) | No | [](https://travis-ci.org/lukechilds/keyv-mysql) [](https://coveralls.io/github/lukechilds/keyv-mysql?branch=master)
## 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 });
```
The following are third-party storage adapters compatible with Keyv:
- [quick-lru](https://github.com/sindresorhus/quick-lru) - Simple "Least Recently Used" (LRU) cache
- [keyv-file](https://github.com/zaaack/keyv-file) - File system storage adapter for Keyv
- [keyv-dynamodb](https://www.npmjs.com/package/keyv-dynamodb) - DynamoDB storage adapter for Keyv
## 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, or any other storage that implements the `Map` API.
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({
uri: typeof opts.cache === 'string' && opts.cache,
store: typeof opts.cache !== 'string' && 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' });
// Some third-party module that implements the Map API
const awesomeModule = new AwesomeModule({ cache: some3rdPartyStore });
```
## 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.serialize
Type: `Function`<br>
Default: `JSONB.stringify`
A custom serialization function.
#### options.deserialize
Type: `Function`<br>
Default: `JSONB.parse`
A custom deserialization function.
#### 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
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