artskydj / tiny-level-ttl

:hourglass: Enforces a time to live (TTL) on a levelup database

tiny-level-ttl

A tiny javascript module that enforces a time to live (TTL) on a node-levelup database.

• The ttl is specified in the constructor. (In node-level-ttl you can set the ttl in the constructor, and/or in a db.put() call.)
• Supports level-sublevel 5 & 6, and level-spaces 1 & 2. (Defaults to level-spaces@2.)
• Respects level-lock locks.

Why use this instead of node-level-ttl? Because level-sublevel and node-level-ttl conflict.

Bug reproduction test code here.
The bug was found using level-sublevel@6 with level-ttl@2, and level-sublevel@5 with level-ttl 0.6.

api

var ttl = require('tiny-level-ttl')

ttl(db[, opts])

Adds a refreshTtl method to the db. When db.refreshTtl(key) is called, it will refresh the ttl on the key. This adds the ability to make the ttl act like a session manager by calling refreshTtl() every time you do db.get().

Also, this respects the locks that level-lock creates. If tiny-level-ttl attempts to delete a key, and the key's write access is locked, it will restart the key's life. (In most cases, this is the desired outcome. If the key is being written to, you would've restarted the key's life anyway. If the key is being deleted, restarting its life will not mess anything up.)

• db is a levelup database.
• opts is an object with the following properties:
  • ttl is a number of milliseconds for how long a key lives in the db. Optional; defaults to 3600000, (1 hour).
  • checkInterval is a number of milliseconds for how long the interval between checking keys is. Optional; defaults to 10000, (10 seconds).
  • separator can be a string, buffer, or array of strings/buffers. These represent the separator used in the sub-database. For example, level-spaces by default has the separator ~, so if you store the key bar, in the space foo, the key will be ~foo~bar. Defaults to [ '~', '\xff', '\x00' ].

example

Basic usage:

var level = require('level-mem')
var ttl = require('tiny-level-ttl')

var db = level('/levelmem/does/not/care')
ttl(db, {
	ttl: 1000,
	checkInterval: 50
})

db.put('hi', 'wuzzup') //this sets the ttl

setTimeout(function () { //before key expires
	db.get('hi', function (err, value) {
		console.log(err && err.notFound) // -> null
		console.log(value) // -> 'wazzup'
	})
}, 900)

setTimeout(function () { //after key expires
	db.get('hi', function (err, value) {
		console.log(err && err.notFound) // -> true
		console.log(value) // -> undefined
	})
}, 1100)

install

With npm do:

npm install tiny-level-ttl

license

VOL

tiny-level-ttl's Issues

Add '!' to default separator list

Add the '!' character to the default separator list. It seems that level-sublevel@6 uses it as a separator.

Note: This might not be needed. I don't think a level-sublevel database will expose a child database's keys using db.createReadStream(). Make sure that it's needed before making a breaking change.

shutdown on db.close

The listeners should be cleaned up when the database closes.

return `refreshTtl`

Should return refreshTtl instead of exposing it on db.refreshTtl.

test that a buffer works as a separator

In the readme it says that a buffer or an array of buffers work as a separator. Test that!