Merge branch 'MDL-55916-maintmode-503-moodle' of https://github.com/brendanheywood/moodle

lib/setup.php

@@ -313,6 +313,9 @@ if (!defined('WS_SERVER')) {
 // Detect CLI maintenance mode - this is useful when you need to mess with database, such as during upgrades
 if (file_exists("$CFG->dataroot/climaintenance.html")) {
     if (!CLI_SCRIPT) {
+        header($_SERVER['SERVER_PROTOCOL'] . ' 503 Moodle under maintenance');
+        header('Status: 503 Moodle under maintenance');
+        header('Retry-After: 300');
         header('Content-type: text/html; charset=utf-8');
         header('X-UA-Compatible: IE=edge');
         /// Headers to make it not cacheable and json

lib/weblib.php

@@ -2934,6 +2934,10 @@ function rebuildnolinktag($text) {
 function print_maintenance_message() {
     global $CFG, $SITE, $PAGE, $OUTPUT;
 
+    header($_SERVER['SERVER_PROTOCOL'] . ' 503 Moodle under maintenance');
+    header('Status: 503 Moodle under maintenance');
+    header('Retry-After: 300');
+
     $PAGE->set_pagetype('maintenance-message');
     $PAGE->set_pagelayout('maintenance');
     $PAGE->set_title(strip_tags($SITE->fullname));