From 24cea1011d8fef8d9d0ab032cf879ba41942daa3 Mon Sep 17 00:00:00 2001
From: Jeff Wolski <wolski@uber.com>
Date: Sun, 21 Jun 2015 12:30:28 -0700
Subject: [PATCH] Have dissemination component subscribe to ringChanged to
 reduce times piggyback count adjustment is evaluated

---
 lib/dissemination.js                  | 23 ++++++++++++++---
 lib/membership.js                     |  1 -
 test/{index_test.js => index-test.js} | 37 +++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 5 deletions(-)
 rename test/{index_test.js => index-test.js} (91%)

diff --git a/lib/dissemination.js b/lib/dissemination.js
index 3b9b9b26..3202960b 100644
--- a/lib/dissemination.js
+++ b/lib/dissemination.js
@@ -17,20 +17,24 @@
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
-
 'use strict';
 
+var EventEmitter = require('events').EventEmitter;
+var util = require('util');
+
 var LOG_10 = Math.log(10);
 
 function Dissemination(ringpop) {
     this.ringpop = ringpop;
-    this.ringpop.on('changed', this.onRingChanged.bind(this));
+    this.ringpop.on('ringChanged', this.onRingChanged.bind(this));
 
     this.changes = {};
-    this.maxPiggybackCount = 1;
-    this.piggybackFactor = 15; // A lower piggyback factor leads to more full-syncs
+    this.maxPiggybackCount = Dissemination.Defaults.maxPiggybackCount;
+    this.piggybackFactor = Dissemination.Defaults.piggybackFactor;
 }
 
+util.inherits(Dissemination, EventEmitter);
+
 Dissemination.prototype.adjustMaxPiggybackCount = function adjustMaxPiggybackCount() {
     var serverCount = this.ringpop.ring.getServerCount();
     var prevPiggybackCount = this.maxPiggybackCount;
@@ -45,6 +49,8 @@ Dissemination.prototype.adjustMaxPiggybackCount = function adjustMaxPiggybackCou
             piggybackFactor: this.piggybackFactor,
             serverCount: serverCount
         });
+
+        this.emit('maxPiggybackCountAdjusted');
     }
 };
 
@@ -126,4 +132,13 @@ Dissemination.prototype.recordChange = function recordChange(change) {
     this.changes[change.address] = change;
 };
 
+Dissemination.prototype.resetMaxPiggybackCount = function resetMaxPiggybackCount() {
+    this.maxPiggybackCount = Dissemination.Defaults.maxPiggybackCount;
+};
+
+Dissemination.Defaults = {
+    maxPiggybackCount: 1,
+    piggybackFactor: 15 // A lower piggyback factor leads to more full-syncs
+};
+
 module.exports = Dissemination;
diff --git a/lib/membership.js b/lib/membership.js
index 7ef821c5..5333dcee 100644
--- a/lib/membership.js
+++ b/lib/membership.js
@@ -17,7 +17,6 @@
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
-
 'use strict';
 
 var _ = require('underscore');
diff --git a/test/index_test.js b/test/index-test.js
similarity index 91%
rename from test/index_test.js
rename to test/index-test.js
index be19d5e5..a91d3a6e 100644
--- a/test/index_test.js
+++ b/test/index-test.js
@@ -24,6 +24,7 @@ var recvAdminLeave = require('../lib/admin-leave-recvr.js');
 var recvJoin = require('../lib/swim/join-recvr.js');
 var Ringpop = require('../index.js');
 var test = require('tape');
+var testRingpop = require('./lib/test-ringpop.js');
 
 function createRingpop(opts) {
     return new Ringpop(_.extend({
@@ -406,6 +407,42 @@ test('emits ring changed event', function t(assert) {
     assert.end();
 });
 
+testRingpop('max piggyback not adjusted on membership update', function t(deps, assert) {
+    assert.plan(0);
+
+    var dissemination = deps.dissemination;
+    var membership = deps.membership;
+
+    dissemination.on('maxPiggybackCountAdjusted', function onAdjusted() {
+        assert.fail('max piggyback count was adjusted');
+    });
+
+    // Reset count to prove that it goes unmodified.
+    dissemination.resetMaxPiggybackCount();
+
+    var address = '127.0.0.1:3002';
+    var incarnationNumber = Date.now();
+    membership.makeSuspect(address, incarnationNumber);
+});
+
+testRingpop('max piggyback adjusted on new members', function t(deps, assert) {
+    assert.plan(1);
+
+    var dissemination = deps.dissemination;
+    var membership = deps.membership;
+
+    dissemination.on('maxPiggybackCountAdjusted', function onAdjusted() {
+        assert.pass('max piggyback count was adjusted');
+    });
+
+    // Reset count to prove that it is modified.
+    dissemination.resetMaxPiggybackCount();
+
+    var address = '127.0.0.1:3002';
+    var incarnationNumber = Date.now();
+    membership.makeAlive(address, incarnationNumber);
+});
+
 test('first time member, not alive', function t(assert) {
     var ringpop = createRingpop();
     ringpop.membership.makeAlive(ringpop.whoami(), Date.now());