Listen on queue via BLPOP rather than pub/sub

services/document-updater/app.coffee

@@ -3,8 +3,9 @@ http = require("http")
 Settings = require('settings-sharelatex')
 logger = require('logger-sharelatex')
 logger.initialize("documentupdater")
-RedisManager = require('./app/js/RedisManager.js')
+RedisManager = require('./app/js/RedisManager')
-UpdateManager = require('./app/js/UpdateManager.js')
+UpdateManager = require('./app/js/UpdateManager')
+WorkersManager = require('./app/js/WorkersManager')
 Keys = require('./app/js/RedisKeyBuilder')
 redis = require('redis')
 Errors = require "./app/js/Errors"
@@ -32,7 +33,9 @@ rclient.on "message", (channel, doc_key) ->
 		UpdateManager.processOutstandingUpdatesWithLock project_id, doc_id, (error) ->
 			logger.error err: error, project_id: project_id, doc_id: doc_id, "error processing update" if error?
 	else
-		logger.log project_id: project_id, doc_id: doc_id, "ignoring incoming update" 
+		logger.log project_id: project_id, doc_id: doc_id, "ignoring incoming update"
+
+WorkersManager.createAndStartWorkers(Settings.workerCount || 10)
 
 UpdateManager.resumeProcessing()
 

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

@@ -0,0 +1,43 @@
+Settings = require('settings-sharelatex')
+logger = require('logger-sharelatex')
+Keys = require('./RedisKeyBuilder')
+redis = require('redis')
+UpdateManager = require('./UpdateManager')
+
+module.exports = WorkersManager =
+	createWorker: () ->
+		redisConf = Settings.redis.web
+		client = redis.createClient(redisConf.port, redisConf.host)
+		client.auth(redisConf.password)
+		
+		worker = {
+			client: client
+			waitForAndProcessUpdate: (callback = (error) ->) ->
+				worker.client.blpop "pending-updates-list", 0, (error, result) ->
+					return callback(error) if error?
+					return callback() if !result?
+					[list_name, doc_key] = result
+					[project_id, doc_id] = Keys.splitProjectIdAndDocId(doc_key)
+					UpdateManager.processOutstandingUpdatesWithLock project_id, doc_id, (error) ->
+						logger.error err: error, project_id: project_id, doc_id: doc_id, "error processing update" if error?
+						return callback(error) if error?
+						return callback()
+						
+			run: () ->
+				return if Settings.shuttingDown
+				worker.waitForAndProcessUpdate (error) =>
+					if error?
+						logger.error err: error, "Error in worker process, waiting 1 second before continuing"
+						setTimeout () ->
+							worker.run()
+						, 1000
+					else
+						worker.run()
+		}
+		
+		return worker
+		
+	createAndStartWorkers: (number) ->
+		for i in [1..number]
+			worker = WorkersManager.createWorker()
+			worker.run()

services/document-updater/test/acceptance/coffee/helpers/DocUpdaterClient.coffee

@@ -14,7 +14,7 @@ module.exports = DocUpdaterClient =
 			doc_key = "#{project_id}:#{doc_id}"
 			rclient.sadd "DocsWithPendingUpdates", doc_key, (error) ->
 				return callback(error) if error?
-				rclient.publish "pending-updates", doc_key, callback
+				rclient.rpush "pending-updates-list", doc_key, callback
 
 	sendUpdates: (project_id, doc_id, updates, callback = (error) ->) ->
 		DocUpdaterClient.preloadDoc project_id, doc_id, (error) ->

services/document-updater/test/unit/coffee/WorkersManager/WorkersManagerTests.coffee

@@ -0,0 +1,73 @@
+sinon = require('sinon')
+chai = require('chai')
+should = chai.should()
+modulePath = "../../../../app/js/WorkersManager.js"
+SandboxedModule = require('sandboxed-module')
+
+describe "WorkersManager", ->
+	beforeEach ->
+		@WorkersManager = SandboxedModule.require modulePath, requires:
+			"./UpdateManager" : @UpdateManager = {}
+			"logger-sharelatex": @logger = { log: sinon.stub() }
+			"settings-sharelatex": @settings =
+				redis:
+					web: {}
+			"redis": @redis = {}
+		@callback = sinon.stub()
+
+	describe "each worker", ->
+		beforeEach ->
+			@client =
+				auth: sinon.stub()
+			@redis.createClient = sinon.stub().returns @client
+			
+			@worker = @WorkersManager.createWorker()
+			
+		it "should create a new redis client", ->
+			@redis.createClient.called.should.equal true
+			
+		describe "waitForAndProcessUpdate", ->
+			beforeEach ->
+				@project_id = "project-id-123"
+				@doc_id = "doc-id-123"
+				@doc_key = "#{@project_id}:#{@doc_id}"
+				@client.blpop = sinon.stub().callsArgWith(2, null, ["pending-updates-list", @doc_key])
+				@UpdateManager.processOutstandingUpdatesWithLock = sinon.stub().callsArg(2)
+				
+				@worker.waitForAndProcessUpdate @callback
+				
+			it "should call redis with BLPOP", ->
+				@client.blpop
+					.calledWith("pending-updates-list", 0)
+					.should.equal true
+					
+			it "should call processOutstandingUpdatesWithLock", ->
+				@UpdateManager.processOutstandingUpdatesWithLock
+					.calledWith(@project_id, @doc_id)
+					.should.equal true
+					
+			it "should call the callback", ->
+				@callback.called.should.equal true
+				
+		describe "run", ->
+			it "should call waitForAndProcessUpdate until shutting down", (done) ->
+				callCount = 0
+				@worker.waitForAndProcessUpdate = (callback = (error) ->) =>
+					callCount++
+					if callCount == 3
+						@settings.shuttingDown = true
+					setTimeout () ->
+						callback()
+					, 10
+				sinon.spy @worker, "waitForAndProcessUpdate"
+				
+			
+				@worker.run()
+				
+				setTimeout () =>
+					@worker.waitForAndProcessUpdate.callCount.should.equal 3
+					done()
+				, 100
+					
+			
+