From 82da35fd516c72e9b1ed0779051babab1faaa7e2 Mon Sep 17 00:00:00 2001
From: Adam Eijdenberg <adam@continusec.com>
Date: Tue, 28 Feb 2017 13:21:58 +1100
Subject: [PATCH] MDL-58018 core: Enable read-only sessions for key pages

These pages are often loaded in parallel.
---
 lib/ajax/getnavbranch.php            |  1 +
 lib/ajax/service.php                 |  2 ++
 lib/db/services.php                  |  2 ++
 lib/externallib.php                  | 10 ++++++++++
 message/output/popup/db/services.php |  1 +
 pluginfile.php                       |  1 +
 6 files changed, 17 insertions(+)

diff --git a/lib/ajax/getnavbranch.php b/lib/ajax/getnavbranch.php
index 17b2668d5ca..76db3f42fe8 100644
--- a/lib/ajax/getnavbranch.php
+++ b/lib/ajax/getnavbranch.php
@@ -26,6 +26,7 @@
  */
 
 define('AJAX_SCRIPT', true);
+define('REQUIRE_SESSION_LOCK', false);
 
 /** Include config */
 require_once(__DIR__ . '/../../config.php');
diff --git a/lib/ajax/service.php b/lib/ajax/service.php
index 3bcb8e9621e..098f806ec5e 100644
--- a/lib/ajax/service.php
+++ b/lib/ajax/service.php
@@ -28,6 +28,8 @@
  */
 
 define('AJAX_SCRIPT', true);
+// Services can declare 'requiresessionlock' in their config located in db/services.php, if not present will default to true.
+define('REQUIRE_SESSION_LOCK', false);
 
 if (!empty($_GET['nosessionupdate'])) {
     define('NO_SESSION_UPDATE', true);
diff --git a/lib/db/services.php b/lib/db/services.php
index a9c81066c08..1e96a514211 100644
--- a/lib/db/services.php
+++ b/lib/db/services.php
@@ -748,6 +748,7 @@ $functions = array(
         'type' => 'read',
         'loginrequired' => false,
         'ajax' => true,
+        'requiresessionlock' => true, // Fetching removes from stack.
     ),
     'core_session_touch' => array(
         'classname' => 'core\session\external',
@@ -1374,6 +1375,7 @@ $functions = array(
         'type' => 'read',
         'ajax' => true,
         'services' => array(MOODLE_OFFICIAL_MOBILE_SERVICE),
+        'requiresessionlock' => false, // We don't modify the session.
     ),
     'core_message_mark_all_notifications_as_read' => array(
         'classname' => 'core_message_external',
diff --git a/lib/externallib.php b/lib/externallib.php
index 24002e0bc44..4cb626b7996 100644
--- a/lib/externallib.php
+++ b/lib/externallib.php
@@ -161,6 +161,11 @@ class external_api {
             } else {
                 $function->loginrequired = true;
             }
+            if (isset($functions[$function->name]['requiresessionlock'])) {
+                $function->requiresessionlock = $functions[$function->name]['requiresessionlock'];
+            } else {
+                $function->requiresessionlock = true;
+            }
         }
 
         return $function;
@@ -184,6 +189,11 @@ class external_api {
 
         $externalfunctioninfo = static::external_function_info($function);
 
+        // Eventually this should shift into the various handlers and not be handled via config.
+        if ($externalfunctioninfo->requiresessionlock) {
+            \core\session\manager::restart_with_write_lock();
+        }
+
         $currentpage = $PAGE;
         $currentcourse = $COURSE;
         $response = array();
diff --git a/message/output/popup/db/services.php b/message/output/popup/db/services.php
index 89809e4115c..f7a5d833f57 100644
--- a/message/output/popup/db/services.php
+++ b/message/output/popup/db/services.php
@@ -41,5 +41,6 @@ $functions = array(
         'type' => 'read',
         'ajax' => true,
         'services' => array(MOODLE_OFFICIAL_MOBILE_SERVICE),
+        'requiresessionlock' => false,
     ),
 );
diff --git a/pluginfile.php b/pluginfile.php
index 24e6cda10e9..76742f9ee50 100644
--- a/pluginfile.php
+++ b/pluginfile.php
@@ -28,6 +28,7 @@
 if (!defined('NO_DEBUG_DISPLAY')) {
     define('NO_DEBUG_DISPLAY', true);
 }
+define('REQUIRE_SESSION_LOCK', false); // Plugins will need to acquire a lock if they need one.
 
 require_once('config.php');
 require_once('lib/filelib.php');