Awesome

Gossip: Cyclon in Javascript

Attention: this is work in progress and things may break!

This implements the Cyclon gossip protocol [1] for membership management.

Gossip in simple language

Imagine you have big group of people and you want to tell everybody something. You could broadcast a message by talking to each of them individually, or you could just talk to some (this is called gossip), telling them to tell other people.

Illustration by @virginialonso

Cyclon in simple language

Cyclon is a simple gossip protocol that ensures that every peer in the network gets connected with the network of peers, without being connected to every single one. This is done by peers keeping a list of neighbors (small compared to the network) and at every interval, ask the neighbor that has been the longest in a peer list of neighbors (this is called partial view), to exchange some neighbors.

Cyclon

const CyclonPeer = require('gossip-cyclon')
const parallel = require('run-parallel')

const Alice = new CyclonPeer()
const Bob = new CyclonPeer()

Alice.addPeers([Bob.me])

parallel([
  () => Alice.listen()
  () => Bob.listen()
], (err) => {
  if (!err) {
    Alice.start()
    Bob.start()
    // This will make Alice and Bob exchange each others information every 1 second
  }
})

Run the visualization

To help understand the protocol, I wrote a visualization that you can run with the following instructions. You can add new peers or click on existing peers to trigger a shuffle. Find the rest of the code here

$ git clone https://github.com/nicola/js-gossip-cyclon
$ cd js-gossip-cyclon
$ npm install
$ node viz/index.js
// Now visit http://127.0.0.1:8080

Usage

constructor

var peer = new CyclonPeer(opts)

opts can have:

• peer: PeerInfo object of this CyclonPeer, default: new PeerInfo().
• maxShuffle: how many peers to send during shuffling
• maxPeers: how many peers can be stored in the list of neighboors (or .partialView)
• interval: how often CyclonPeer should shuffle
• peers: array of peers to bootstrap CyclonPeer (they will be added to its .partialView)

variables

peer.partialView

Partial view of the peer, this is a PeerSet

peer.peer

The current peer object, by default a PeerInfo

methods

peer.listen(cb)

Listen on its transports (by default TCP)

peer.close(cb)

Close any listener on any transport

peer.start()

Start shuffling every peer.interval

peer.stop()

Stops the repeating shuffling

peer.shuffle(cb)

Shuffle and when done calls cb (on failure or success)

peer.addPeers(peers, replace)

Add a list of peers, if the peers to be added will make .partialView grow beyond .maxPeers, the replace list will be used, otherwise drop 'em.

peer.updateAge()

Update the age of the peers in the .partialView

References

[1] S. Voulgaris, D. Gavidia, M. van Steen. CYCLON: Inexpensive Membership Management for Unstructured P2P Overlays. J. Network Syst. Manage. 13(2): 197-217 (2005)

License

MIT