Exchange checksums in join response for higher performance join respo…

…nse merging
esatterwhite · Jul 1, 2015 · d4f2a21 · d4f2a21
1 parent 00e6533
commit d4f2a21
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Showing 3 changed files with 36 additions and 5 deletions.
diff --git a/benchmarks/join-response-merge.js b/benchmarks/join-response-merge.js
@@ -27,11 +27,11 @@ function reportPerformance(event) {
     console.log(event.target.toString());
 }
 
-function benchMerge() {
+function benchMerge(title, checksum) {
     var responses = [];
 
     var suite = new Suite();
-    suite.add('merge 3 responses of 1000 members', benchThis);
+    suite.add(title, benchThis);
     suite.on('start', init);
     suite.on('cycle', reportPerformance);
     suite.run();
@@ -45,10 +45,20 @@ function benchMerge() {
 
         for (var i = 0; i < 3; i++) {
             responses.push({
-                members: members1k
+                members: members1k,
+                checksum: checksum
             });
         }
     }
 }
 
-benchMerge();
+function benchMergeNoChecksum() {
+    benchMerge('merge 3 responses of 1000 members with no checksum');
+}
+
+function benchMergeSameChecksum() {
+    benchMerge('merge 3 responses of 1000 members with same checksum', 123456789);
+}
+
+benchMergeNoChecksum();
+benchMergeSameChecksum();
diff --git a/lib/swim/join-recvr.js b/lib/swim/join-recvr.js
@@ -92,6 +92,7 @@ module.exports = function recvJoin(opts, callback) {
     callback(null, {
         app: ringpop.app,
         coordinator: ringpop.whoami(),
-        membership: ringpop.dissemination.fullSync()
+        membership: ringpop.dissemination.fullSync(),
+        membershipChecksum: ringpop.membership.checksum
     });
 };
diff --git a/lib/swim/join-response-merge.js b/lib/swim/join-response-merge.js
@@ -19,11 +19,31 @@
 // THE SOFTWARE.
 'use strict';
 
+function hasSameChecksums(joinResponses) {
+    var lastChecksum = -1;
+
+    for (var i = 0; i < joinResponses.length; i++) {
+        var response = joinResponses[i];
+
+        if (!response.checksum || (lastChecksum !== -1 && lastChecksum !== response.checksum)) {
+            return false;
+        }
+
+        lastChecksum = response.checksum;
+    }
+
+    return true;
+}
+
 function mergeJoinResponses(joinResponses) {
     if (!Array.isArray(joinResponses) || joinResponses.length === 0) {
         return [];
     }
 
+    if (hasSameChecksums(joinResponses)) {
+        return joinResponses[0].members;
+    }
+
     var mergeIndex = {};
 
     for (var i = 0; i < joinResponses.length; i++) {