Add option to ringpop for cross platform mode,

In cross platform mode it uses farmhash’s fingerprint32 instead of hash32 to guarantee consistent hashes across different platforms. Currently cross platform mode is disabled by default to be backwards compatible with running installations of ringpop. This might change in the future.

config.js

@@ -57,6 +57,7 @@ Config.prototype._seed = function _seed(seed) {
     // All config names should be camel-cased.
     seedOrDefault('TEST_KEY', 100); // never remove, tests and lives depend on it
     seedOrDefault('autoGossip', true);
+    seedOrDefault('isCrossPlatform', false);
     seedOrDefault('dampScoringEnabled', true);
     seedOrDefault('dampScoringDecayEnabled', true);
     seedOrDefault('dampScoringDecayInterval', 1000);

index.js

@@ -35,6 +35,7 @@
 var _ = require('underscore');
 var EventEmitter = require('events').EventEmitter;
 var fs = require('fs');
+var farmhash = require('farmhash');
 var globalSetTimeout = require('timers').setTimeout;
 var hammock = require('uber-hammock');
 var metrics = require('metrics');
@@ -123,14 +124,23 @@ function RingPop(options) {
     // and hash ring dependencies.
     this.config = new Config(this, options);
 
+    // use fingerprint if ringpop needs to function cross different platforms
+    if (this.config.get('isCrossPlatform')) {
+        this.hashFunc = farmhash.fingerprint32;
+    } else {
+        this.hashFunc = farmhash.hash32;
+    }
+
     this.requestProxy = new RequestProxy({
         ringpop: this,
         maxRetries: options.requestProxyMaxRetries,
         retrySchedule: options.requestProxyRetrySchedule,
         enforceConsistency: options.enforceConsistency
     });
 
-    this.ring = new this.Ring();
+    this.ring = new this.Ring({
+        hashFunc: this.hashFunc
+    });
 
     this.dissemination = new Dissemination(this);
 

lib/membership/index.js

@@ -21,7 +21,6 @@
 
 var _ = require('underscore');
 var EventEmitter = require('events').EventEmitter;
-var farmhash = require('farmhash');
 var Member = require('./member.js');
 var mergeMembershipChangesets = require('./merge.js');
 var timers = require('timers');
@@ -62,7 +61,7 @@ Membership.prototype.computeChecksum = function computeChecksum() {
     var start = new Date();
 
     var prevChecksum = this.checksum;
-    this.checksum = farmhash.fingerprint32(this.generateChecksumString());
+    this.checksum = this.ringpop.hashFunc(this.generateChecksumString());
 
     this.emit('checksumComputed');
     this.ringpop.stat('timing', 'compute-checksum', start);

lib/ring/index.js

@@ -26,7 +26,7 @@ function HashRing(options) {
     this.options = options || {};
 
     this.replicaPoints = this.options.replicaPoints || 100;
-    this.hashFunc = this.options.hashFunc || farmhash.fingerprint32;
+    this.hashFunc = this.options.hashFunc || farmhash.hash32;
 
     this.rbtree = new RBTree();
     this.servers = {};

main.js

@@ -46,7 +46,8 @@ function main(args) {
         logger: createLogger('ringpop'),
         channel: tchannel.makeSubChannel({
             serviceName: 'ringpop'
-        })
+        }),
+        isCrossPlatform: true
     });
 
     ringpop.setupChannel();