add /debug/events endpoint

services/real-time/app.coffee

@@ -53,6 +53,11 @@ app.get "/", (req, res, next) ->
 app.get "/status", (req, res, next) ->
 	res.send "real-time-sharelatex is alive"
 
+app.get "/debug/events", (req, res, next) ->
+	Settings.debugEvents = parseInt(req.query?.count,10) || 20
+	logger.log {count: Settings.debugEvents}, "starting debug mode"
+	res.send "debug mode will log next #{Settings.debugEvents} events"
+
 rclient = require("redis-sharelatex").createClient(Settings.redis.realtime)
 app.get "/health_check/redis", (req, res, next) ->
 	rclient.healthCheck (error) ->

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

@@ -15,6 +15,7 @@ module.exports = DocumentUpdaterController =
 	listenForUpdatesFromDocumentUpdater: (io) ->
 		rclient.subscribe "applied-ops"
 		rclient.on "message", (channel, message) ->
+			EventLogger.debugEvent(channel, message) if settings.debugEvents > 0
 			DocumentUpdaterController._processMessageFromDocumentUpdater(io, channel, message)
 		
 	_processMessageFromDocumentUpdater: (io, channel, message) ->

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

@@ -1,5 +1,6 @@
 logger = require 'logger-sharelatex'
 metrics = require 'metrics-sharelatex'
+settings = require 'settings-sharelatex'
 
 # keep track of message counters to detect duplicate and out of order events
 # messsage ids have the format "UNIQUEHOSTKEY-COUNTER"
@@ -8,10 +9,18 @@ EVENT_LOG_COUNTER = {}
 EVENT_LOG_TIMESTAMP = {}
 EVENT_LAST_CLEAN_TIMESTAMP = 0
 
+# counter for debug logs
+COUNTER = 0
+
 module.exports = EventLogger =
 
 	MAX_STALE_TIME_IN_MS: 3600 * 1000
 
+	debugEvent: (channel, message) ->
+		if settings.debugEvents > 0
+			logger.log {channel:channel, message:message, counter: COUNTER++}, "logging event"
+			settings.debugEvents--
+
 	checkEventOrder: (channel, message_id, message) ->
 		return if typeof(message_id) isnt 'string'
 		return if !(result = message_id.match(/^(.*)-(\d+)$/))

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

@@ -27,6 +27,7 @@ module.exports = WebsocketLoadBalancer =
 	listenForEditorEvents: (io) ->
 		@rclientSub.subscribe "editor-events"
 		@rclientSub.on "message", (channel, message) ->
+			EventLogger.debugEvent(channel, message) if Settings.debugEvents > 0
 			WebsocketLoadBalancer._processEditorEvent io, channel, message
 
 	_processEditorEvent: (io, channel, message) ->