redis-key-down

Redis backend for LevelUP

Requirements:

• redis-2.8 or more recent.
• node-12.x

This is a fork of the excellent redisdown. Like the original, it uses a sorted-set to order the keys, but the values are stored as individual keys to make sure that key eviction will not flush all the data when using Redis as an LRU cache.

Fetches the ordered key value pairs during iterations with a single redis lua call.

Abstract-LevelDOWN testsuite is green.

Example

Copied and pasted from the levelup documentation. Added the db option when creating the db to use redis-key-down.

var levelup = require('levelup')
var redisKeyDown = require('redis-key-down')

// 1) Create our database, supply location and options.
//    This will create or open the underlying LevelDB store.
var db = levelup('mydb', { db: redisKeyDown, host: 'localhost', port: 6379 })

// If you use sentinel/cluster mode, you must use a single slot to store the values thanks to a `{hash}`
//var db = levelup('{thehash}path', { db: redisKeyDown });

// if you already have a redis client
//var db = levelup('mydb', { db: redisKeyDown, redis: redisClient })

// if you use an URL environment variable
//var db = levelup('mydb', { db: redisKeyDown, url: process.env.REDIS_URL })
// if you use Redis Cloud on Heroku
//var db = levelup('mydb', { db: redisKeyDown, url: process.env.REDISCLOUD_URL })

// 2) put a key & value
db.put('name', 'LevelUP', function (err) {
  if (err) return console.log('Ooops!', err) // some kind of I/O error

  // 3) fetch by key
  db.get('name', function (err, value) {
    if (err) return console.log('Ooops!', err) // likely the key was not found

    // ta da!
    console.log('name=' + value)
  })
})

API

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redisKeyDown(location)

redisKeyDown(location) returns a new RedisDOWN instance. location is a String pointing at the root namespace of the data in redis.

• location+'$'+key is where the values are stored.
• location+':z' is the set where the keys are sorted.

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redisKeyDown#open([options, ]callback)

open() is an instance method on an existing database object.

options is a hash that is passed to the redis library to create a redis client:

• highWaterMark number of values to fetch in one redis call for iteration. Defaults to 256.
• port redis port. Defaults to '127.0.0.1'
• host redis host. Defaults to 6379
• redis already configured redis client. redisKeyDown will not open or close it. host and port and all other redis options are ignored.
• Other options: https://github.com/mranney/node_redis#rediscreateclientport-host-options

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redisKeyDown.destroy(location, [options, ]callback)

destroy(location) is used to completely delete all data in redis related to the location.

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redisKeyDown#batch([{type: 'put', key: 'foo1', value: 'bar1' [, prefix: 'subsection']}, ...])

batch() supports an exra property prefix to store/retrieve/delete a key in a specific namespace of the redis DB. It is useful to support sublevel-ish batch operations: https://github.com/dominictarr/level-sublevel#batches and is well supported by redis.

By default, the prefix is a string that is the path to the where redis stores the document. In order to resolve other types of prefixes, one would need to override the #__getPrefix(prefix) method. Passing a levelup instance is demonstrated here: https://github.com/hmalphettes/redisdown/blob/master/test/batch-prefix-test.js#L12

Pouchdb integrations tests: all 3605 of them

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npm run-script test-pouchdb-redis

The script will install the extra required dependencies. It works for me.