support multple redis instances for pubsub

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

@@ -1,7 +1,6 @@
 logger = require "logger-sharelatex"
 settings = require 'settings-sharelatex'
 redis = require("redis-sharelatex")
-rclient = redis.createClient(settings.redis.pubsub)
 SafeJsonParse = require "./SafeJsonParse"
 EventLogger = require "./EventLogger"
 HealthCheckManager = require "./HealthCheckManager"
@@ -12,13 +11,15 @@ MESSAGE_SIZE_LOG_LIMIT = 1024 * 1024 # 1Mb
 module.exports = DocumentUpdaterController =
 	# DocumentUpdaterController is responsible for updates that come via Redis
 	# Pub/Sub from the document updater.
+	rclientList: [redis.createClient(settings.redis.pubsub)]
 
 	listenForUpdatesFromDocumentUpdater: (io) ->
-		rclient.subscribe "applied-ops"
-		rclient.on "message", (channel, message) ->
-			metrics.inc "rclient", 0.001 # global event rate metric
-			EventLogger.debugEvent(channel, message) if settings.debugEvents > 0
-			DocumentUpdaterController._processMessageFromDocumentUpdater(io, channel, message)
+		for rclient in @rclientList
+			rclient.subscribe "applied-ops"
+			rclient.on "message", (channel, message) ->
+				metrics.inc "rclient", 0.001 # global event rate metric
+				EventLogger.debugEvent(channel, message) if settings.debugEvents > 0
+				DocumentUpdaterController._processMessageFromDocumentUpdater(io, channel, message)
 		
 	_processMessageFromDocumentUpdater: (io, channel, message) ->
 		SafeJsonParse.parse message, (error, message) ->

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

@@ -2,14 +2,12 @@ Settings = require 'settings-sharelatex'
 logger = require 'logger-sharelatex'
 redis = require("redis-sharelatex")
 SafeJsonParse = require "./SafeJsonParse"
-rclientPub = redis.createClient(Settings.redis.pubsub)
-rclientSub = redis.createClient(Settings.redis.pubsub)
 EventLogger = require "./EventLogger"
 HealthCheckManager = require "./HealthCheckManager"
 
 module.exports = WebsocketLoadBalancer =
-	rclientPub: rclientPub
-	rclientSub: rclientSub
+	rclientPubList: [redis.createClient(Settings.redis.pubsub)]
+	rclientSubList: [redis.createClient(Settings.redis.pubsub)]
 
 	emitToRoom: (room_id, message, payload...) ->
 		if !room_id?
@@ -20,16 +18,18 @@ module.exports = WebsocketLoadBalancer =
 			message: message
 			payload: payload
 		logger.log {room_id, message, payload, length: data.length}, "emitting to room"
-		@rclientPub.publish "editor-events", data
+		for rclientPub in @rclientPubList
+			rclientPub.publish "editor-events", data
 
 	emitToAll: (message, payload...) ->
 		@emitToRoom "all", message, payload...
 
 	listenForEditorEvents: (io) ->
-		@rclientSub.subscribe "editor-events"
-		@rclientSub.on "message", (channel, message) ->
-			EventLogger.debugEvent(channel, message) if Settings.debugEvents > 0
-			WebsocketLoadBalancer._processEditorEvent io, channel, message
+		for rclientSub in @rclientSubList
+			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) ->
 		SafeJsonParse.parse message, (error, message) ->

services/real-time/test/unit/coffee/DocumentUpdaterControllerTests.coffee

@@ -10,6 +10,7 @@ describe "DocumentUpdaterController", ->
 		@doc_id = "doc-id-123"
 		@callback = sinon.stub()
 		@io = { "mock": "socket.io" }
+		@rclient = []
 		@EditorUpdatesController = SandboxedModule.require modulePath, requires:
 			"logger-sharelatex": @logger = { error: sinon.stub(), log: sinon.stub(), warn: sinon.stub() }
 			"settings-sharelatex": @settings =
@@ -17,9 +18,11 @@ describe "DocumentUpdaterController", ->
 					documentupdater:
 						key_schema:
 							pendingUpdates: ({doc_id}) -> "PendingUpdates:#{doc_id}"
-			"redis-sharelatex" : 
-				createClient: () => 
-					@rclient = {}
+					pubsub: null
+			"redis-sharelatex" : @redis =
+				createClient: (name) =>
+					@rclient.push(rclientStub = {name:name})
+					return rclientStub
 			"./SafeJsonParse": @SafeJsonParse =
 				parse: (data, cb) => cb null, JSON.parse(data)
 			"./EventLogger": @EventLogger = {checkEventOrder: sinon.stub()}
@@ -28,15 +31,23 @@ describe "DocumentUpdaterController", ->
 
 	describe "listenForUpdatesFromDocumentUpdater", ->
 		beforeEach ->
-			@rclient.subscribe = sinon.stub()
-			@rclient.on = sinon.stub()
+			@rclient.length = 0  # clear any existing clients
+			@EditorUpdatesController.rclientList = [@redis.createClient("first"), @redis.createClient("second")]
+			@rclient[0].subscribe = sinon.stub()
+			@rclient[0].on = sinon.stub()
+			@rclient[1].subscribe = sinon.stub()
+			@rclient[1].on = sinon.stub()
 			@EditorUpdatesController.listenForUpdatesFromDocumentUpdater()
 		
 		it "should subscribe to the doc-updater stream", ->
-			@rclient.subscribe.calledWith("applied-ops").should.equal true
+			@rclient[0].subscribe.calledWith("applied-ops").should.equal true
 
 		it "should register a callback to handle updates", ->
-			@rclient.on.calledWith("message").should.equal true
+			@rclient[0].on.calledWith("message").should.equal true
+
+		it "should subscribe to any additional doc-updater stream", ->
+			@rclient[1].subscribe.calledWith("applied-ops").should.equal true
+			@rclient[1].on.calledWith("message").should.equal true
 
 	describe "_processMessageFromDocumentUpdater", ->
 		describe "with bad JSON", ->

services/real-time/test/unit/coffee/WebsocketLoadBalancerTests.coffee

@@ -15,11 +15,12 @@ describe "WebsocketLoadBalancer", ->
 			"./EventLogger": {checkEventOrder: sinon.stub()}
 			"./HealthCheckManager": {check: sinon.stub()}
 		@io = {}
-		@WebsocketLoadBalancer.rclientPub = publish: sinon.stub()
-		@WebsocketLoadBalancer.rclientSub =
+		@WebsocketLoadBalancer.rclientPubList = [{publish: sinon.stub()}]
+		@WebsocketLoadBalancer.rclientSubList = [{
 			subscribe: sinon.stub()
 			on: sinon.stub()
-		
+		}]
+
 		@room_id = "room-id"
 		@message = "message-to-editor"
 		@payload = ["argument one", 42]
@@ -29,7 +30,7 @@ describe "WebsocketLoadBalancer", ->
 			@WebsocketLoadBalancer.emitToRoom(@room_id, @message, @payload...)
 
 		it "should publish the message to redis", ->
-			@WebsocketLoadBalancer.rclientPub.publish
+			@WebsocketLoadBalancer.rclientPubList[0].publish
 				.calledWith("editor-events", JSON.stringify(
 					room_id: @room_id,
 					message: @message
@@ -53,12 +54,12 @@ describe "WebsocketLoadBalancer", ->
 			@WebsocketLoadBalancer.listenForEditorEvents()
 
 		it "should subscribe to the editor-events channel", ->
-			@WebsocketLoadBalancer.rclientSub.subscribe
+			@WebsocketLoadBalancer.rclientSubList[0].subscribe
 				.calledWith("editor-events")
 				.should.equal true
 
 		it "should process the events with _processEditorEvent", ->
-			@WebsocketLoadBalancer.rclientSub.on
+			@WebsocketLoadBalancer.rclientSubList[0].on
 				.calledWith("message", sinon.match.func)
 				.should.equal true