JarCasting
Simple key-value storage with support for multiple backends
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 inside another module
- Works with any storage that implements the
MapAPI - Handles all JSON types plus
Buffer - Supports namespaces
- Wide range of efficient, well tested 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.
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.
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 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.
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 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 | Yes |   |
| MongoDB | @keyv/mongo | Yes |   |
| SQLite | @keyv/sqlite | No |   |
| PostgreSQL | @keyv/postgres | No |   |
| MySQL | @keyv/mysql | No |   |
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.
const Keyv = require('keyv');
const myAdapter = require('./my-storage-adapter');
const keyv = new Keyv({ store: myAdapter });
Any store that follows the Map api will work.
new Keyv({ store: new Map() });
For example, quick-lru is a completely unrelated module that implements the Map API.
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 - Simple "Least Recently Used" (LRU) cache
- keyv-file - File system storage adapter for Keyv
- keyv-dynamodb - DynamoDB storage adapter for Keyv
- keyv-firestore – Firebase Cloud Firestore adapter for Keyv
- keyv-mssql - Microsoft Sql Server adapter for Keyv
- keyv-memcache - Memcache 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:
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:
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
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
Default: 'keyv'
Namespace for the current instance.
options.ttl
Type: Number
Default: undefined
Default TTL. Can be overridden by specififying a TTL on .set().
options.serialize
Type: Function
Default: JSONB.stringify
A custom serialization function.
options.deserialize
Type: Function
Default: JSONB.parse
A custom deserialization function.
options.store
Type: Storage adapter instance
Default: new Map()
The storage adapter instance to be used by Keyv.
options.adapter
Type: String
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 a promise which resolves to true.
.get(key, [options])
Returns a promise which resolves to the retrieved value.
options.raw
Type: Boolean
Default: false
If set to true the raw DB object Keyv stores internally will be returned instead of just the value.
This contains the TTL timestamp.
.delete(key)
Deletes an entry.
Returns a promise which resolves to true if the key existed, false if not.
.clear()
Delete all entries in the current namespace.
Returns a promise which is resolved when the entries have been cleared.
License
MIT © Luke Childs