refactored Acceptor to use Proposal objects for state.

It's probably worth while to not share proposal.js for
Acceptor state *and* as a message between actors.

acceptor/acceptor.js

@@ -1,52 +1,46 @@
-module.exports = function (assert, inherits, EventEmitter) {
+module.exports = function (assert, inherits, EventEmitter, Proposal) {
 
 	function Acceptor(id, learner, storage) {
 		EventEmitter.call(this)
 		this.id = id
-		this.learner = learner || nilLearner
+		this.learner = learner
 		this.learner.on('data', onlearnerData.bind(this))
 		this.storage = storage || nilStorage
 		this.highmark = this.learner.highmark()
 		this.instances = {}
 	}
 	inherits(Acceptor, EventEmitter)
 
-	Acceptor.prototype.prepare = function (prepare) {
-		assert.equal(prepare.valueBallot, undefined)
+	Acceptor.prototype.instance = function (id) {
+		var instance = this.instances[id] || Proposal.create(id, this.id)
+		this.instances[id] = instance
+		return instance
+	}
 
+	Acceptor.prototype.prepare = function (prepare) {
 		if (prepare.instance <= this.highmark) {
 			return this.lookup(prepare.instance, 'promised')
 		}
 
-		var state = this.instances[prepare.instance] || prepare
-
-		if (state.ballot <= prepare.ballot && !state.valueBallot) {
-			// Promise to reject lower ballots, but
-			// if a proposal has already been accepted don't touch it
-			state = prepare
-		}
-		state.acceptor = this.id
-		this.instances[prepare.instance] = state
-		this.storage.set(state, this.emit.bind(this, 'promised'))
+		var proposal = this.instance(prepare.instance).prepare(prepare)
+		this.storage.set(proposal, this.emit.bind(this, 'promised'))
 	}
 
 	Acceptor.prototype.accept = function (proposal) {
-		var state = this.instances[proposal.instance] || proposal
-
 		if (proposal.instance <= this.highmark) {
-			return this.lookup(proposal.instance, 'accepted')
+			return this.lookup(proposal.instance, 'rejected')
 		}
-		if (state.ballot > proposal.ballot) {
-			// refuse the proposal by replying with the higher ballot proposal
-			return this.emit('rejected', state)
+
+		var instance = this.instance(proposal.instance)
+		var accepted = instance.accept(proposal)
+		if (accepted) {
+			return this.storage.set(accepted, this.emit.bind(this, 'accepted'))
 		}
-		proposal.acceptor = this.id
-		this.instances[proposal.instance] = proposal
-		this.storage.set(proposal, this.emit.bind(this, 'accepted'))
+		this.emit('rejected', instance)
 	}
 
-	Acceptor.prototype.lookup = function (instance, event) {
-		this.storage.get(instance, this.emit.bind(this, event || 'lookup'))
+	Acceptor.prototype.lookup = function (instanceId, event) {
+		this.storage.get(instanceId, this.emit.bind(this, event || 'lookup'))
 	}
 
 	function onlearnerData(proposal) {
@@ -55,7 +49,6 @@ module.exports = function (assert, inherits, EventEmitter) {
 		delete this.instances[proposal.instance]
 	}
 
-	var nilLearner = { highmark: function () { return 0 }, on: function () {}}
 	var nilStorage = { get: function (i) { }, set: function (p, cb) { cb(p) }}
 
 	return Acceptor

acceptor/index.js

@@ -2,6 +2,7 @@ var assert = require('assert')
 var EventEmitter = require('events').EventEmitter
 var inherits = require('util').inherits
 
-var Acceptor = require('./acceptor')(assert, inherits, EventEmitter)
+var Proposal = require('../lib/proposal')()
+var Acceptor = require('./acceptor')(assert, inherits, EventEmitter, Proposal)
 
 module.exports = Acceptor

lib/proposal.js

@@ -8,6 +8,25 @@ module.exports = function () {
 		this.acceptor = acceptor
 	}
 
+	Proposal.create = function (instance, acceptor) {
+		return new Proposal(instance, 0, null, 0, acceptor)
+	}
+
+	Proposal.prototype.prepare = function (prepare) {
+		this.ballot = Math.max(prepare.ballot, this.ballot)
+		return this
+	}
+
+	Proposal.prototype.accept = function (proposal) {
+		if (this.ballot > proposal.ballot) {
+			return
+		}
+		this.ballot = proposal.ballot
+		this.valueBallot = proposal.ballot
+		this.value = proposal.value
+		return this
+	}
+
 	Proposal.prototype.copy = function () {
 		return new Proposal(this.instance, this.ballot, this.value, this.valueBallot, this.acceptor)
 	}

proposer/propose-state.js

@@ -71,7 +71,6 @@ module.exports = function (assert, inherits, EventEmitter, Prepare, Proposal) {
 				this.value = highest.value
 				// otherwise there were no accepted proposals
 			}
-			this.valueBallot = this.ballot
 			return this.proposal()
 		}
 	}

test/acceptor-tests.js

@@ -3,17 +3,18 @@ var inherits = require('util').inherits
 var EventEmitter = require('events').EventEmitter
 var Proposal = require('../lib/proposal')()
 var Prepare = require('../lib/prepare')()
-var Acceptor = require('../acceptor/acceptor')(assert, inherits, EventEmitter)
+var Acceptor = require('../acceptor/acceptor')(assert, inherits, EventEmitter, Proposal)
 
 describe('Acceptor', function () {
 
 	var acceptor = null
+	var fakeLearner = {on: function () {}, highmark: function () { return 0 }}
 
 	beforeEach(function () {
-		acceptor = new Acceptor(1)
+		acceptor = new Acceptor(1, fakeLearner)
 	})
 
-	describe('prepare', function () {
+	describe('prepare()', function () {
 
 		it('stores the highest ballot',
 			function () {
@@ -22,20 +23,20 @@ describe('Acceptor', function () {
 				var prep3 = new Prepare(1, 3)
 
 				acceptor.prepare(prep2)
-				assert.equal(acceptor.instances[1], prep2)
+				assert.equal(acceptor.instance(1).ballot, prep2.ballot)
 				acceptor.prepare(prep1)
-				assert.equal(acceptor.instances[1], prep2)
+				assert.equal(acceptor.instance(1).ballot, prep2.ballot)
 				acceptor.prepare(prep3)
-				assert.equal(acceptor.instances[1], prep3)
+				assert.equal(acceptor.instance(1).ballot, prep3.ballot)
 			}
 		)
 
 		it('emits the accepted proposal if one exists',
 			function (done) {
-				var proposal1 = new Proposal(4, 3, 'x', 2, 1)
+				var proposal1 = new Proposal(4, 3, 'x')
 				acceptor.accept(proposal1)
 				acceptor.once('promised', function (proposal) {
-					assert.equal(proposal, proposal1)
+					assert.equal(proposal.value, proposal1.value)
 					done()
 				})
 
@@ -44,16 +45,16 @@ describe('Acceptor', function () {
 		)
 	})
 
-	describe('accept', function () {
+	describe('accept()', function () {
 
 		it('does not accept a proposal with a lower ballot',
 			function (done) {
-				var proposal1 = new Proposal(4, 5, 'x', 2, 1)
-				var proposal2 = new Proposal(4, 3, 'x', 2, 1)
+				var proposal1 = new Proposal(4, 5, 'x')
+				var proposal2 = new Proposal(4, 3, 'x')
 
 				acceptor.accept(proposal1)
 				acceptor.once('rejected', function (proposal) {
-					assert.equal(proposal, proposal1)
+					assert.equal(proposal.ballot, proposal1.ballot)
 					done()
 				})
 				acceptor.accept(proposal2)
@@ -63,20 +64,20 @@ describe('Acceptor', function () {
 		it('emits the accepted proposal',
 			function (done) {
 				acceptor.once('accepted', function (proposal) {
-					assert.equal(proposal, proposal1)
+					assert.equal(proposal.ballot, proposal1.ballot)
 					done()
 				})
 
-				var proposal1 = new Proposal(4, 3, 'x', 2, 1)
+				var proposal1 = new Proposal(4, 3, 'x')
 				acceptor.accept(proposal1)
 			}
 		)
 
 		it('accepts the first proposal if no prepare requests have been made',
 			function (done) {
-				var proposal1 = new Proposal(4, 3, 'x', 2, 1)
+				var proposal1 = new Proposal(4, 3, 'x')
 				acceptor.once('accepted', function (proposal) {
-					assert.equal(proposal, proposal1)
+					assert.equal(proposal.ballot, proposal1.ballot)
 					done()
 				})
 				acceptor.accept(proposal1)
@@ -86,9 +87,9 @@ describe('Acceptor', function () {
 		it('refuses a proposal if a prepare request had a higher ballot',
 			function (done) {
 				var prep1 = new Prepare(4, 5)
-				var proposal1 = new Proposal(4, 3, 'x', 2, 1)
+				var proposal1 = new Proposal(4, 3, 'x')
 				acceptor.once('rejected', function (proposal) {
-					assert.equal(proposal, prep1)
+					assert.equal(proposal.ballot, prep1.ballot)
 					done()
 				})
 				acceptor.prepare(prep1)