only flush to track-changes when ops are queued

services/document-updater/app/coffee/DocumentManager.coffee

@@ -91,7 +91,7 @@ module.exports = DocumentManager =
 				logger.log project_id: project_id, doc_id: doc_id, version: version, "flushing doc"
 				PersistenceManager.setDoc project_id, doc_id, lines, version, (error) ->
 					return callback(error) if error?
-					TrackChangesManager.flushDocChanges project_id, doc_id,  (error) ->
+					TrackChangesManager.flushDocChangesIfNeeded project_id, doc_id,  (error) ->
 						return callback(error) if error?
 						callback null
 

services/document-updater/app/coffee/RedisManager.coffee

@@ -171,6 +171,9 @@ module.exports = RedisManager =
 			[length, _] = results
 			callback(error, length)
 
+	getUncompressedHistoryOpLength: (doc_id, callback = (error, length) ->) ->
+		rclient.llen keys.uncompressedHistoryOp(doc_id: doc_id), callback
+
 	getDocOpsLength: (doc_id, callback = (error, length) ->) ->
 		rclient.llen keys.docOps(doc_id: doc_id), callback
 

services/document-updater/app/coffee/TrackChangesManager.coffee

@@ -5,6 +5,16 @@ RedisManager = require "./RedisManager"
 crypto = require("crypto")
 
 module.exports = TrackChangesManager =
+
+	flushDocChangesIfNeeded: (project_id, doc_id, callback = (error) ->) ->
+		RedisManager.getUncompressedHistoryOpLength doc_id, (error, length) ->
+			return callback(error) if error?
+			if length > 0
+				# only make request to track changes if there are queued ops
+				TrackChangesManager.flushDocChanges project_id, doc_id, callback
+			else
+				callback()
+
 	flushDocChanges: (project_id, doc_id, callback = (error) ->) ->
 		if !settings.apis?.trackchanges?
 			logger.warn doc_id: doc_id, "track changes API is not configured, so not flushing"