[misc] stop processing requests as we detect a client disconnect

v2 expose `client.connected`; v0 exposes `client.disconnected`

(cherry-picked from commit a9d70484343ca9be367d45bf7bb949e4be449647)

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

@@ -16,11 +16,18 @@ module.exports = WebsocketController =
 	PROTOCOL_VERSION: 2
 
 	joinProject: (client, user, project_id, callback = (error, project, privilegeLevel, protocolVersion) ->) ->
+		if client.disconnected
+			metrics.inc('disconnected_join_project')
+			return callback()
+
 		user_id = user?._id
 		logger.log {user_id, project_id, client_id: client.id}, "user joining project"
 		metrics.inc "editor.join-project"
 		WebApiManager.joinProject project_id, user, (error, project, privilegeLevel, isRestrictedUser) ->
 			return callback(error) if error?
+			if client.disconnected
+				metrics.inc('disconnected_join_project')
+				return callback()
 
 			if !privilegeLevel or privilegeLevel == ""
 				err = new Error("not authorized")
@@ -77,6 +84,10 @@ module.exports = WebsocketController =
 			, WebsocketController.FLUSH_IF_EMPTY_DELAY
 
 	joinDoc: (client, doc_id, fromVersion = -1, options, callback = (error, doclines, version, ops, ranges) ->) ->
+		if client.disconnected
+				metrics.inc('disconnected_join_doc')
+				return callback()
+
 		metrics.inc "editor.join-doc"
 		Utils.getClientAttributes client, ["project_id", "user_id", "is_restricted_user"], (error, {project_id, user_id, is_restricted_user}) ->
 			return callback(error) if error?
@@ -89,8 +100,17 @@ module.exports = WebsocketController =
 				# doc to the client, so that no events are missed.
 				RoomManager.joinDoc client, doc_id, (error) ->
 					return callback(error) if error?
+					if client.disconnected
+						metrics.inc('disconnected_join_doc')
+						# the client will not read the response anyways
+						return callback()
+
 					DocumentUpdaterManager.getDocument project_id, doc_id, fromVersion, (error, lines, version, ranges, ops) ->
 						return callback(error) if error?
+						if client.disconnected
+							metrics.inc('disconnected_join_doc')
+							# the client will not read the response anyways
+							return callback()
 
 						if is_restricted_user and ranges?.comments?
 							ranges.comments = []
@@ -122,6 +142,7 @@ module.exports = WebsocketController =
 						callback null, escapedLines, version, ops, ranges
 
 	leaveDoc: (client, doc_id, callback = (error) ->) ->
+		# client may have disconnected, but we have to cleanup internal state.
 		metrics.inc "editor.leave-doc"
 		Utils.getClientAttributes client, ["project_id", "user_id"], (error, {project_id, user_id}) ->
 			logger.log {user_id, project_id, doc_id, client_id: client.id}, "client leaving doc"
@@ -132,6 +153,10 @@ module.exports = WebsocketController =
 			## AuthorizationManager.removeAccessToDoc client, doc_id
 			callback()
 	updateClientPosition: (client, cursorData, callback = (error) ->) ->
+		if client.disconnected
+				# do not create a ghost entry in redis
+				return callback()
+
 		metrics.inc "editor.update-client-position", 0.1
 		Utils.getClientAttributes client, [
 			"project_id", "first_name", "last_name", "email", "user_id"
@@ -173,6 +198,10 @@ module.exports = WebsocketController =
 
 	CLIENT_REFRESH_DELAY: 1000
 	getConnectedUsers: (client, callback = (error, users) ->) ->
+		if client.disconnected
+				# they are not interested anymore, skip the redis lookups
+				return callback()
+
 		metrics.inc "editor.get-connected-users"
 		Utils.getClientAttributes client, ["project_id", "user_id", "is_restricted_user"], (error, clientAttributes) ->
 			return callback(error) if error?
@@ -192,6 +221,7 @@ module.exports = WebsocketController =
 				, WebsocketController.CLIENT_REFRESH_DELAY
 
 	applyOtUpdate: (client, doc_id, update, callback = (error) ->) ->
+		# client may have disconnected, but we can submit their update to doc-updater anyways.
 		Utils.getClientAttributes client, ["user_id", "project_id"], (error, {user_id, project_id}) ->
 			return callback(error) if error?
 			return callback(new Error("no project_id found on client")) if !project_id?
@@ -223,6 +253,9 @@ module.exports = WebsocketController =
 						# trigger an out-of-sync error
 						message = {project_id, doc_id, error: "update is too large"}
 						setTimeout () ->
+							if client.disconnected
+								# skip the message broadcast, the client has moved on
+								return metrics.inc('disconnected_otUpdateError')
 							client.emit "otUpdateError", message.error, message
 							client.disconnect()
 						, 100

services/real-time/test/acceptance/coffee/EarlyDisconnect.coffee

@@ -0,0 +1,160 @@
+async = require "async"
+{expect} = require("chai")
+
+RealTimeClient = require "./helpers/RealTimeClient"
+MockDocUpdaterServer = require "./helpers/MockDocUpdaterServer"
+MockWebServer = require "./helpers/MockWebServer"
+FixturesManager = require "./helpers/FixturesManager"
+
+settings = require "settings-sharelatex"
+redis = require "redis-sharelatex"
+rclient = redis.createClient(settings.redis.pubsub)
+rclientRT = redis.createClient(settings.redis.realtime)
+KeysRT = settings.redis.realtime.key_schema
+
+describe "EarlyDisconnect", ->
+	before (done) ->
+		MockDocUpdaterServer.run done
+
+	describe "when the client disconnects before joinProject completes", ->
+		before () ->
+			# slow down web-api requests to force the race condition
+			@actualWebAPIjoinProject = joinProject = MockWebServer.joinProject
+			MockWebServer.joinProject = (project_id, user_id, cb) ->
+				setTimeout () ->
+					joinProject(project_id, user_id, cb)
+				, 300
+
+		after () ->
+			MockWebServer.joinProject = @actualWebAPIjoinProject
+
+		beforeEach (done) ->
+			async.series [
+				(cb) =>
+					FixturesManager.setUpProject {
+						privilegeLevel: "owner"
+						project: {
+							name: "Test Project"
+						}
+					}, (e, {@project_id, @user_id}) => cb()
+
+				(cb) =>
+					@clientA = RealTimeClient.connect()
+					@clientA.on "connectionAccepted", cb
+
+				(cb) =>
+					@clientA.emit "joinProject", project_id: @project_id, (() ->)
+					# disconnect before joinProject completes
+					@clientA.on "disconnect", () -> cb()
+					@clientA.disconnect()
+
+				(cb) =>
+					# wait for joinDoc and subscribe
+					setTimeout cb, 500
+			], done
+
+		# we can force the race condition, there is no need to repeat too often
+		for attempt in Array.from(length: 5).map((_, i) -> i+1)
+			it "should not subscribe to the pub/sub channel anymore (race #{attempt})", (done) ->
+				rclient.pubsub 'CHANNELS', (err, resp) =>
+					return done(err) if err
+					expect(resp).to.not.include "editor-events:#{@project_id}"
+					done()
+				return null
+
+	describe "when the client disconnects before joinDoc completes", ->
+		beforeEach (done) ->
+			async.series [
+				(cb) =>
+					FixturesManager.setUpProject {
+						privilegeLevel: "owner"
+						project: {
+							name: "Test Project"
+						}
+					}, (e, {@project_id, @user_id}) => cb()
+
+				(cb) =>
+					@clientA = RealTimeClient.connect()
+					@clientA.on "connectionAccepted", cb
+
+				(cb) =>
+					@clientA.emit "joinProject", project_id: @project_id, (error, @project, @privilegeLevel, @protocolVersion) =>
+						cb(error)
+
+				(cb) =>
+					FixturesManager.setUpDoc @project_id, {@lines, @version, @ops}, (e, {@doc_id}) =>
+						cb(e)
+
+				(cb) =>
+					@clientA.emit "joinDoc", @doc_id, (() ->)
+					# disconnect before joinDoc completes
+					@clientA.on "disconnect", () -> cb()
+					@clientA.disconnect()
+
+				(cb) =>
+					# wait for subscribe and unsubscribe
+					setTimeout cb, 100
+			], done
+
+		# we can not force the race condition, so we have to try many times
+		for attempt in Array.from(length: 20).map((_, i) -> i+1)
+			it "should not subscribe to the pub/sub channels anymore (race #{attempt})", (done) ->
+				rclient.pubsub 'CHANNELS', (err, resp) =>
+					return done(err) if err
+					expect(resp).to.not.include "editor-events:#{@project_id}"
+
+					rclient.pubsub 'CHANNELS', (err, resp) =>
+						return done(err) if err
+						expect(resp).to.not.include "applied-ops:#{@doc_id}"
+						done()
+				return null
+
+	describe "when the client disconnects before clientTracking.updatePosition starts", ->
+		beforeEach (done) ->
+			async.series [
+				(cb) =>
+					FixturesManager.setUpProject {
+						privilegeLevel: "owner"
+						project: {
+							name: "Test Project"
+						}
+					}, (e, {@project_id, @user_id}) => cb()
+
+				(cb) =>
+					@clientA = RealTimeClient.connect()
+					@clientA.on "connectionAccepted", cb
+
+				(cb) =>
+					@clientA.emit "joinProject", project_id: @project_id, (error, @project, @privilegeLevel, @protocolVersion) =>
+						cb(error)
+
+				(cb) =>
+					FixturesManager.setUpDoc @project_id, {@lines, @version, @ops}, (e, {@doc_id}) =>
+						cb(e)
+
+				(cb) =>
+					@clientA.emit "joinDoc", @doc_id, cb
+
+				(cb) =>
+					@clientA.emit "clientTracking.updatePosition", {
+							row: 42
+							column: 36
+							doc_id: @doc_id
+						}, (() ->)
+					# disconnect before updateClientPosition completes
+					@clientA.on "disconnect", () -> cb()
+					@clientA.disconnect()
+
+				(cb) =>
+					# wait for updateClientPosition
+					setTimeout cb, 100
+			], done
+
+		# we can not force the race condition, so we have to try many times
+		for attempt in Array.from(length: 20).map((_, i) -> i+1)
+			it "should not show the client as connected (race #{attempt})", (done) ->
+				rclientRT.smembers KeysRT.clientsInProject({project_id: @project_id}), (err, results) ->
+					return done(err) if err
+					expect(results).to.deep.equal([])
+					done()
+				return null

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

@@ -20,6 +20,7 @@ describe 'WebsocketController', ->
 		}
 		@callback = sinon.stub()
 		@client =
+			disconnected: false
 			id: @client_id = "mock-client-id-123"
 			params: {}
 			set: sinon.stub()
@@ -147,6 +148,35 @@ describe 'WebsocketController', ->
 					.should.equal true
 				@callback.args[0][0].message.should.equal "subscribe failed"
 
+		describe "when the client has disconnected", ->
+			beforeEach ->
+				@client.disconnected = true
+				@WebApiManager.joinProject = sinon.stub().callsArg(2)
+				@WebsocketController.joinProject @client, @user, @project_id, @callback
+
+			it "should not call WebApiManager.joinProject", ->
+				expect(@WebApiManager.joinProject.called).to.equal(false)
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal []
+
+			it "should increment the disconnected_join_project metric", ->
+				expect(@metrics.inc.calledWith("disconnected_join_project")).to.equal(true)
+
+		describe "when the client disconnects while WebApiManager.joinProject is running", ->
+			beforeEach ->
+				@WebApiManager.joinProject = (project, user, cb) =>
+					@client.disconnected = true
+					cb(null, @project, @privilegeLevel, @isRestrictedUser)
+
+				@WebsocketController.joinProject @client, @user, @project_id, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal []
+
+			it "should increment the disconnected_join_project metric", ->
+				expect(@metrics.inc.calledWith("disconnected_join_project")).to.equal(true)
+
 	describe "leaveProject", ->
 		beforeEach ->
 			@DocumentUpdaterManager.flushProjectToMongoAndDelete = sinon.stub().callsArg(1)
@@ -384,6 +414,51 @@ describe 'WebsocketController', ->
 				ranges = @callback.args[0][4]
 				expect(ranges.comments).to.deep.equal []
 
+		describe "when the client has disconnected", ->
+			beforeEach ->
+				@client.disconnected = true
+				@WebsocketController.joinDoc @client, @doc_id, -1, @options, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal([])
+
+			it "should increment the disconnected_join_doc metric", ->
+				expect(@metrics.inc.calledWith("disconnected_join_doc")).to.equal(true)
+
+			it "should not get the document", ->
+				expect(@DocumentUpdaterManager.getDocument.called).to.equal(false)
+
+		describe "when the client disconnects while RoomManager.joinDoc is running", ->
+			beforeEach ->
+				@RoomManager.joinDoc = (client, doc_id, cb) =>
+					@client.disconnected = true
+					cb()
+
+				@WebsocketController.joinDoc @client, @doc_id, -1, @options, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal([])
+
+			it "should increment the disconnected_join_doc metric", ->
+				expect(@metrics.inc.calledWith("disconnected_join_doc")).to.equal(true)
+
+			it "should not get the document", ->
+				expect(@DocumentUpdaterManager.getDocument.called).to.equal(false)
+
+		describe "when the client disconnects while DocumentUpdaterManager.getDocument is running", ->
+			beforeEach ->
+				@DocumentUpdaterManager.getDocument = (project_id, doc_id, fromVersion, callback) =>
+					@client.disconnected = true
+					callback(null, @doc_lines, @version, @ranges, @ops)
+
+				@WebsocketController.joinDoc @client, @doc_id, -1, @options, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal []
+
+			it "should increment the disconnected_join_doc metric", ->
+				expect(@metrics.inc.calledWith("disconnected_join_doc")).to.equal(true)
+
 	describe "leaveDoc", ->
 		beforeEach ->
 			@doc_id = "doc-id-123"
@@ -463,6 +538,18 @@ describe 'WebsocketController', ->
 					.called
 					.should.equal false
 
+		describe "when the client has disconnected", ->
+			beforeEach ->
+				@client.disconnected = true
+				@AuthorizationManager.assertClientCanViewProject = sinon.stub()
+				@WebsocketController.getConnectedUsers @client, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal([])
+
+			it "should not check permissions", ->
+				expect(@AuthorizationManager.assertClientCanViewProject.called).to.equal(false)
+
 	describe "updateClientPosition", ->
 		beforeEach ->
 			@WebsocketLoadBalancer.emitToRoom = sinon.stub()
@@ -642,6 +729,18 @@ describe 'WebsocketController', ->
 				@ConnectedUsersManager.updateUserPosition.called.should.equal false
 				done()
 
+		describe "when the client has disconnected", ->
+			beforeEach ->
+				@client.disconnected = true
+				@AuthorizationManager.assertClientCanViewProjectAndDoc = sinon.stub()
+				@WebsocketController.updateClientPosition @client, @update, @callback
+
+			it "should call the callback with no details", ->
+				expect(@callback.args[0]).to.deep.equal([])
+
+			it "should not check permissions", ->
+				expect(@AuthorizationManager.assertClientCanViewProjectAndDoc.called).to.equal(false)
+
 	describe "applyOtUpdate", ->
 		beforeEach ->
 			@update = {op: {p: 12, t: "foo"}}
@@ -715,7 +814,7 @@ describe 'WebsocketController', ->
 				@WebsocketController.applyOtUpdate @client, @doc_id, @update, @callback
 				setTimeout ->
 					done()
-				, 201
+				, 1
 
 			it "should call the callback with no error", ->
 				@callback.called.should.equal true
@@ -727,11 +826,29 @@ describe 'WebsocketController', ->
 					@user_id, @project_id, @doc_id, updateSize: 7372835
 				}, 'update is too large']
 
-			it "should send an otUpdateError the client", ->
+			describe "after 100ms", ->
-				@client.emit.calledWith('otUpdateError').should.equal true
+				beforeEach (done) ->
+					setTimeout done, 100
 
-			it "should disconnect the client", ->
+				it "should send an otUpdateError the client", ->
-				@client.disconnect.called.should.equal true
+					@client.emit.calledWith('otUpdateError').should.equal true
+
+				it "should disconnect the client", ->
+					@client.disconnect.called.should.equal true
+
+			describe "when the client disconnects during the next 100ms", ->
+				beforeEach (done) ->
+					@client.disconnected = true
+					setTimeout done, 100
+
+				it "should not send an otUpdateError the client", ->
+					@client.emit.calledWith('otUpdateError').should.equal false
+
+				it "should not disconnect the client", ->
+					@client.disconnect.called.should.equal false
+
+				it "should increment the disconnected_otUpdateError metric", ->
+					expect(@metrics.inc.calledWith("disconnected_otUpdateError")).to.equal(true)
 
 	describe "_assertClientCanApplyUpdate", ->
 		beforeEach ->