scuttlebutt

scuttlebutt

<img src=https://secure.travis-ci.org/dominictarr/scuttlebutt.png?branch=master>

A base class that makes implementing datastructures for real-time replication easy.

This seems like a silly name, but I assure you, this is real science. read this: http://www.cs.cornell.edu/home/rvr/papers/flowgossip.pdf

or if you are lazy: http://en.wikipedia.org/wiki/Scuttlebutt (lazyness will get you nowhere, btw)

Usage

subclasses must implement at least histroy and applyUpdate

Scuttlebutt#histroy(sources)

sources is a hash of source_ids: timestamps. histroy must return an array of all known events from all sources That occur after the given timestamps for each source.

The array MUST be in order by timestamp.

{ A: 0,
  B: 2,
  C: 3 }

Scuttlebutt#applyUpdate (update)

Possibly apply a given update to the subclasses model. return true if the update was applied. (see scuttlebutt/model.js for an example of a subclass that does not apply every update)

Examples

var Model = require('scuttlebutt/model')

var a = new Model()
var b = new Model()

a.set(key, value)

b.on('update', console.log)

var s = a.createStream()
s.pipe(b.createStream()).pipe(s)

scuttlebutt subclasses

Any Scuttlebutt subclass is replicated with createStream.

var s = new Scuttlebutt()
var z = new Scuttlebutt()
var zs = z.createStream()

zs.pipe(s.createStream()).pipe(zs)

scuttlebutt/ReliableEventEmitter

A Reliable event emmitter. Multiple instances of an emitter may be connected to each other and will remember events, so that they may be resent after a disconnection or crash.

With this approach it is also possible to persist events to disk, making them durable over crashes.

var Emitter = require('scuttlebutt/events')
var emitter = new Emitter()

emit (event, data)

emit an event. only one argument is permitted.

on (event, listener)

add an event listener.

scuttlebutt/Model

A replicateable Model object.

var Model = require('scuttlebutt/model')
var model = new Model()

get (key)

Get a property

set (key, value)

Set a property

on('update', function (key, value, source))

Emmitted when a property changes. If source !== this.id then it was a remote update.