redis-tag-cache

Cache and invalidate records in Redis with tags.

Installation

``sh
yarn add redis-tag-cache


or


npm install redis-tag-cache
`

Demo Usage

`js
import TagCache from 'redis-tag-cache';

const cache = new TagCache({
defaultTimeout: 86400 // Expire records after a day (even if they weren't invalidated)
});

/*
* Cache some records tagged with IDs
*/

// Store two posts by the same author
await cache.set(
'post:id-123',
{ id: 'id-123', title: 'Hello world', author: 'user-123' },
['id-123', 'user-123']
);
await cache.set(
'post:id-234',
{ id: 'id-234', title: 'Hello world again', author: 'user-123' },
['id-234', 'user-123']
);
// And a third post by a different author
// and set a custom timeout for it
await cache.set(
'post:id-345',
{ id: 'id-345', title: 'Hello world again', author: 'user-234' },
['id-345', 'user-234'],
{ timeout: 604800 / Cache for a week / }
);

/*
* Retrieve records by their ID
*/

console.log(await cache.get('post:id-234')) // => { id: 'id-234', title: 'Hello world again', author: 'user-123' }

/*
* Invalidate records by their tags
*/

// Invalidate all records tagged with user-123
await cache.invalidate('user-123');
console.log(await cache.get('post:id-123')) // => null
console.log(await cache.get('post:id-234')) // => null
// The third post not tagged with user-123 is still around!
console.log(await cache.get('post:id-345')) // => { id: 'id-345', title: 'Hello world again', author: 'user-234' }
`

API

$3

`JS
const cache = new TagCache(options);
`

#### options

Options can be an object containing any of the following keys:

- defaultTimeout: number of seconds until records expire even if not invalidated
- redis: any ioredis option, this object is directly passed through to new Redis(ioredisOptions)

Example:

`JS
const cache = new TagCache({
defaultTimeout: 86400,
redis: {
keyPrefix: 'my-cache', // Recommended: set a keyprefix for all keys stored via the cache
port: 6379,
host: 'redis-service.com',
password: 'password',
}
});
`

$3

Store a record in Redis. Usage:

`JS
cache.set(key: string, value: any, tags: Array, options?: Object): Promise
`

#### options

Can have one of the following keys:

- timeout: number of seconds until the record times out, overrides defaultTimeout option

#### Example

`JS
cache.set('some-key', 'some-value', ['some-tag'], { timeout: 123, })cache
.then(() => console.log('Stored successfully!'))
`

$3

Get records from the cache. Usage:

`JS
cache.get(...keys: Array): Promise | ?value>
`

#### Example

`JS
cache.get('existing-key')
.then(data => console.log('Got record!', data));

cache.get('not-existing-key')
.then(data => console.log('data is null', data === null));

cache.get('key-1', 'key-2')
.then(data => console.log('got multiple keys', data[0], data[1]));
`

$3

Invalidate a set of tags and any records associated with them. Usage:

`JS
cache.invalidate(tag1: string, tag2: string, ...): Promise
`

#### Example

`JS
cache.invalidate('some-tag', 'some-other-tag')
.then(() => console.log('Tags invalidated successfully!'))
`

Under the hood

Under the hood we store one set for each tag with all its associated keys and your data as a separate record. For example:

`JS
cache.set('some-key', 'some-value', ['some-tag']);
cache.set('some-other-key', 'some-other-value', ['some-tag', 'some-other-tag'];
`

With these two .set calls you'd end up with these records stored in Redis:

- data:some-key = "some-value"
- data:some-other-key = "some-other-value"
- tags:some-tag = ["some-key", "some-other-key"]
- tags:some-other-tag = ["some-other-key"]

The tradeoff chosen is to keep .get as fast as possible (it's a single redis.get(key), so it couldn't be faster), while making .set a bit slower (since we have to do multiple redis.sets, one for each tags) and .invalidate slow. (since we have to do a redis.get per tag and then a redis.del per record in the tags lists)

PRs implementing this differently under the hood to make .set and/or .invalidate quicker while keeping .get` as fast as it is would be appreciated!

License

Licensed under the MIT License, Copyright ©️ 2018 Maximilian Stoiber. See LICENSE.md for more information.