Add check to prevent scheduling multiple uploads

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 * Add support for passing callback function to init.
 * Fix bug to check that Window localStorage is available for use.
+* Fix bug to prevent scheduling multiple event uploads.
 
 ## 2.4.0 (September 4, 2015)
 

amplitude.js

@@ -165,6 +165,7 @@ Amplitude.prototype._sending = false;
 Amplitude.prototype._lastEventTime = null;
 Amplitude.prototype._sessionId = null;
 Amplitude.prototype._newSession = false;
+Amplitude.prototype._updateScheduled = false;
 
 /**
  * Initializes Amplitude.
@@ -282,7 +283,16 @@ Amplitude.prototype._sendEventsIfReady = function(callback) {
     return true;
   }
 
-  setTimeout(this.sendEvents.bind(this), this.options.eventUploadPeriodMillis);
+  if (!this._updateScheduled) {
+    this._updateScheduled = true;
+    setTimeout(
+      function() {
+        this._updateScheduled = false;
+        this.sendEvents();
+      }.bind(this), this.options.eventUploadPeriodMillis
+    );
+  }
+
   return false;
 };
 

src/amplitude.js

@@ -53,6 +53,7 @@ Amplitude.prototype._sending = false;
 Amplitude.prototype._lastEventTime = null;
 Amplitude.prototype._sessionId = null;
 Amplitude.prototype._newSession = false;
+Amplitude.prototype._updateScheduled = false;
 
 /**
  * Initializes Amplitude.
@@ -170,7 +171,16 @@ Amplitude.prototype._sendEventsIfReady = function(callback) {
     return true;
   }
 
-  setTimeout(this.sendEvents.bind(this), this.options.eventUploadPeriodMillis);
+  if (!this._updateScheduled) {
+    this._updateScheduled = true;
+    setTimeout(
+      function() {
+        this._updateScheduled = false;
+        this.sendEvents();
+      }.bind(this), this.options.eventUploadPeriodMillis
+    );
+  }
+
   return false;
 };
 

test/amplitude.js

@@ -387,7 +387,41 @@ describe('Amplitude', function() {
       assert.lengthOf(amplitude._unsentEvents, 0);
       clock.tick(eventUploadPeriodMillis);
       assert.lengthOf(server.requests, 1);
-    })
+    });
+
+    it('should not schedule more than one upload', function() {
+      var eventUploadPeriodMillis = 5*1000; // 5s
+      amplitude.init(apiKey, null, {
+        batchEvents: true,
+        eventUploadThreshold: 30,
+        eventUploadPeriodMillis: eventUploadPeriodMillis
+      });
+
+      // log 2 events, 1 millisecond apart, second event should not schedule upload
+      amplitude.logEvent('Event1');
+      clock.tick(1);
+      amplitude.logEvent('Event2');
+      assert.lengthOf(amplitude._unsentEvents, 2);
+      assert.lengthOf(server.requests, 0);
+
+      // advance to upload period millis, and should have 1 server request
+      // from the first scheduled upload
+      clock.tick(eventUploadPeriodMillis-1);
+      assert.lengthOf(server.requests, 1);
+      server.respondWith('success');
+      server.respond();
+
+      // log 3rd event, advance 1 more millisecond, verify no 2nd server request
+      amplitude.logEvent('Event3');
+      clock.tick(1);
+      assert.lengthOf(server.requests, 1);
+
+      // the 3rd event, however, should have scheduled another upload after 5s
+      clock.tick(eventUploadPeriodMillis-2);
+      assert.lengthOf(server.requests, 1);
+      clock.tick(1);
+      assert.lengthOf(server.requests, 2);
+    });
 
     it('should back off on 413 status', function() {
       amplitude.init(apiKey, null, {uploadBatchSize: 10});