add continuous background flush

services/document-updater/app.coffee

@@ -14,6 +14,7 @@ if Settings.sentry?.dsn?
 
 RedisManager = require('./app/js/RedisManager')
 DispatchManager = require('./app/js/DispatchManager')
+DeleteQueueManager = require('./app/js/DeleteQueueManager')
 Errors = require "./app/js/Errors"
 HttpController = require "./app/js/HttpController"
 mongojs = require "./app/js/mongojs"
@@ -146,3 +147,7 @@ module.exports = app
 
 for signal in ['SIGINT', 'SIGHUP', 'SIGQUIT', 'SIGUSR1', 'SIGUSR2', 'SIGTERM', 'SIGABRT']
 	process.on signal, shutdownCleanly(signal)
+
+if Settings.continuousBackgroundFlush
+	logger.info "Starting continuous background flush"
+	DeleteQueueManager.startBackgroundFlush()

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

@@ -1,3 +1,4 @@
+Settings = require('settings-sharelatex')
 RedisManager = require "./RedisManager"
 ProjectManager = require "./ProjectManager"
 logger = require "logger-sharelatex"
@@ -60,4 +61,13 @@ module.exports = DeleteQueueManager =
                     count++ if flushed
                     flushNextProject()
 
-        flushNextProject()
+        flushNextProject()
+
+    startBackgroundFlush: () ->
+        doFlush = () ->
+            if Settings.shuttingDown
+                logger.warn "discontinuing background flush due to shutdown"
+                return
+            DeleteQueueManager.flushAndDeleteOldProjects {timeout:1000,min_delete_age:3*60*1000,limit:1000}, () ->
+                setTimeout doFlush, 10
+        doFlush()

services/document-updater/config/settings.defaults.coffee

@@ -95,3 +95,5 @@ module.exports =
 		dsn: process.env.SENTRY_DSN
 
 	publishOnIndividualChannels: process.env['PUBLISH_ON_INDIVIDUAL_CHANNELS'] or false
+
+	continuousBackgroundFlush: process.env['CONTINUOUS_BACKGROUND_FLUSH'] or false