grapevine

gossip protocol - a fork of gossiper module with some added features

npm install grapevine
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Grapevine

A fork of the original node-gossip

grape·vine (grāp′vīn′) n.

  1. A vine on which grapes grow. 2. a. The informal transmission of information, gossip, or rumor from person to person. b. A usually unrevealed source of confidential information.

Added features:

  • instead of msgpack this fork is using json-over-tcp
  • key/value pairs have optional ttl, which propagates to the other peers, it will cause keys to get deleted (although this is not an EXACT mechanism, so it shouldn't be used as such)
  • IPv6 support
  • various bug fixes

node-gossip implements a gossip protocol w/failure detection, allowing you to create a fault-tolerant, self-managing cluster of node.js processes. Each server in the cluster has it's own set of key-value pairs which are propogated to the others peers in the cluster. The API allows you to make changes to the local state, listen for changes in state, listen for new peers and be notified when a peer appears to be dead or appears to have come back to life.

The library is currently in 'hey it seems to work for me' state, there are probably some bugs lurking around. The API will probably change and suggestions on how to improve it are very welcome.

Check out the the scripts in the simulations/ directory for some examples.

Usage

var Gossiper = require('gossiper').Gossiper;
// Create a seed peer.
var seed = new Gossiper(9000, []);
seed.start();

// Create 20 new peers and point them at the seed (usually this would happen in 20 separate processes)
// To prevent having a single point of failure you would probably have multiple seeds
for(var i = 9001; i <= 9020;i++) {
  //For IPv6 peers use the format [ad:dre::ss]:port. e.g. [::1]:9000
  var g = new Gossiper(i, ['127.0.0.1:9000']);
  g.start();

  g.on('update', function(peer, k, v) {
    console.log("peer " + peer + " set " + k + " to " + v); // peer 127.0.0.1:9999 set somekey to somevalue
  });
}

// Add another peer which updates it's state after 15 seconds
var updater = new Gossiper(9999, ['127.0.0.1:9000']);
updater.start();
setTimeout(function() {
  updater.setLocalState('somekey', 'somevalue');

  // with ttl
  updater.setLocalState('somekey', 'somevalue', Date.now() + 10000); // 10 seconds from now this key will start to expire in the gossip net
}, 15000);

API

Gossiper methods:

allPeers()
livePeers()
deadPeers()
peerValue(peer, key)
peerKeys(peer)
getLocalState(key)
setLocalSate(key, value)

Gossiper events:

on('update', function(peer_name, key, value) {})
on('new_peer', function(peer_name) {})
on('peer_alive', function(peer_name) {})
on('peer_failed', function(peer_name) {})

Tests

expresso -I lib test/*

TODO

  • major code refactoring, too many people wrote too much code without proper coordination
  • convert tests to mocha
  • test edge cases
  • Cluster name -- dont allow peers to accidentally join the wrong cluster
  • The scuttlebutt paper mentions a couple things we don't current do:
    • congestion throttling
    • make digests only be random subsets

Acknowledgements

Both the gossip protocol and the failure detection algorithms are based off of academic papers and Cassandra's (http://www.cassandra.org/) implementation of those papers. This library is highly indebted to both.

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