log and skip duplicate events

services/real-time/app/coffee/DocumentUpdaterController.coffee

@@ -24,7 +24,9 @@ module.exports = DocumentUpdaterController =
 				return
 			if message.op?
 				if message._id?
-					EventLogger.checkEventOrder("applied-ops", message._id, message)
+					status = EventLogger.checkEventOrder("applied-ops", message._id, message)
+					if status is 'duplicate'
+						return # skip duplicate events
 				DocumentUpdaterController._applyUpdateFromDocumentUpdater(io, message.doc_id, message.op)
 			else if message.error?
 				DocumentUpdaterController._processErrorFromDocumentUpdater(io, message.doc_id, message.error, message)
@@ -33,6 +35,11 @@ module.exports = DocumentUpdaterController =
 
 	_applyUpdateFromDocumentUpdater: (io, doc_id, update) ->
 		clientList = io.sockets.clients(doc_id)
+		# avoid unnecessary work if no clients are connected
+		if clientList.length is 0
+			return
+		# send updates to clients
+		logger.log doc_id: doc_id, version: update.v, source: update.meta?.source, socketIoClients: (client.id for client in clientList), "distributing updates to clients"
 		seen = {}
 		# send messages only to unique clients (due to duplicate entries in io.sockets.clients)
 		for client in clientList when not seen[client.id]

services/real-time/app/coffee/EventLogger.coffee

@@ -26,11 +26,11 @@ module.exports = EventLogger =
 			return # order is ok
 		if (count == previous)
 			metrics.inc "event.#{channel}.duplicate"
-			# logger.error {key:key, previous: previous, count:count, message:message}, "duplicate event"
+			logger.warn {channel:channel, message_id:message_id}, "duplicate event"
 			return "duplicate"
 		else
 			metrics.inc "event.#{channel}.out-of-order"
-			# logger.error {key:key, previous: previous, count:count, message:message}, "events out of order"
+			logger.warn {channel:channel, message_id:message_id, key:key, previous: previous, count:count}, "out of order event"
 			return "out-of-order"
 
 	_storeEventCount: (key, count) ->

services/real-time/app/coffee/WebsocketLoadBalancer.coffee

@@ -38,9 +38,14 @@ module.exports = WebsocketLoadBalancer =
 				io.sockets.emit(message.message, message.payload...)
 			else if message.room_id?
 				if message._id?
-					EventLogger.checkEventOrder("editor-events", message._id, message)
+					status = EventLogger.checkEventOrder("editor-events", message._id, message)
+					if status is "duplicate"
+						return # skip duplicate events
 				# send messages only to unique clients (due to duplicate entries in io.sockets.clients)
 				clientList = io.sockets.clients(message.room_id)
+				# avoid unnecessary work if no clients are connected
+				return if clientList.length is 0
+				logger.log {channel:channel, message: message.message, room_id: message.room_id, message_id: message._id, socketIoClients: (client.id for client in clientList)}, "distributing event to clients"
 				seen = {}
 				for client in clientList when not seen[client.id]
 					seen[client.id] = true