lock compile directory

app/coffee/LockManager.coffee

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+Settings = require('settings-sharelatex')
+logger = require "logger-sharelatex"
+Lockfile = require('lockfile') # from https://github.com/npm/lockfile
+Errors = require "./Errors"
+
+module.exports = LockManager =
+	LOCK_TEST_INTERVAL: 1000 # 50ms between each test of the lock
+	MAX_LOCK_WAIT_TIME: 15000 # 10s maximum time to spend trying to get the lock
+	LOCK_STALE: 5*60*1000 # 5 mins time until lock auto expires
+
+	runWithLock: (path, runner = ((releaseLock = (error) ->) ->), callback = ((error) ->)) ->
+		lockOpts =
+			wait: @MAX_LOCK_WAIT_TIME
+			pollPeriod: @LOCK_TEST_INTERVAL
+			stale: @LOCK_STALE
+		Lockfile.lock path, lockOpts, (error) ->
+			return callback new Errors.AlreadyCompilingError("compile in progress")	if error?.code is 'EEXIST'
+			return callback(error) if error?
+			runner (error1, args...) ->
+				Lockfile.unlock path, (error2) ->
+					error = error1 or error2
+					return callback(error) if error?
+					callback(null, args...)