From: sam_marshall <sam_marshall>
Date: Mon, 6 Apr 2009 09:48:39 +0000 (+0000)
Subject: MDL-18768: Limited size of context and modinfo caches to avoid memory problems with... 
X-Git-Url: http://git.mjollnir.org/gw?a=commitdiff_plain;h=4d10247fdb2027fb80782262c16838b55217ec7a;p=moodle.git

MDL-18768: Limited size of context and modinfo caches to avoid memory problems with code that loops through many courses, also changed forum role_assign to use recordset for all-courses loops
---

diff --git a/course/lib.php b/course/lib.php
index 2d906cf150..1810a5a18d 100644
--- a/course/lib.php
+++ b/course/lib.php
@@ -22,6 +22,9 @@ define('FIRSTUSEDEXCELROW', 3);
 define('MOD_CLASS_ACTIVITY', 0);
 define('MOD_CLASS_RESOURCE', 1);
 
+if (!defined('MAX_MODINFO_CACHE_SIZE')) { 
+    define('MAX_MODINFO_CACHE_SIZE', 10);
+}
 
 function make_log_url($module, $url) {
     switch ($module) {
@@ -1254,6 +1257,11 @@ function &get_fast_modinfo(&$course, $userid=0) {
     unset($cache[$course->id]); // prevent potential reference problems when switching users
     $cache[$course->id] = $modinfo;
 
+    // Ensure cache does not use too much RAM
+    if (count($cache) > MAX_MODINFO_CACHE_SIZE) {
+        array_shift($cache);
+    }
+
     return $cache[$course->id];
 }
 
diff --git a/lib/accesslib.php b/lib/accesslib.php
index 53019e47ee..17b37cb4e4 100755
--- a/lib/accesslib.php
+++ b/lib/accesslib.php
@@ -161,6 +161,11 @@ define('ROLENAME_BOTH', 2);    // Both, like this:  Role alias (Original)
 define('ROLENAME_ORIGINALANDSHORT', 3); // the name as defined in the role definition and the shortname in brackets
 define('ROLENAME_ALIAS_RAW', 4);   // the name as defined by a role alias, in raw form suitable for editing
 
+// size limit for context cache
+if (!defined('MAX_CONTEXT_CACHE_SIZE')) { 
+    define('MAX_CONTEXT_CACHE_SIZE', 5000);
+}
+
 // Although this looks like a global variable, it isn't really. It is just a private
 // implementation detail to accesslib that MUST NOT be used elsewhere. It is used to
 // cache various bits of data between function calls for performance reasons. Sadly,
@@ -205,6 +210,14 @@ function accesslib_clear_all_caches_for_unit_testing() {
  */
 function cache_context($context) {
     global $ACCESSLIB_PRIVATE;
+
+    // If there are too many items in the cache already, remove items until
+    // there is space
+    while (count($ACCESSLIB_PRIVATE->contextsbyid) >= MAX_CONTEXT_CACHE_SIZE) {
+        $first = array_shift($ACCESSLIB_PRIVATE->contextsbyid);
+        unset($ACCESSLIB_PRIVATE->contexts[$first->contextlevel][$first->instanceid]);
+    }
+
     $ACCESSLIB_PRIVATE->contexts[$context->contextlevel][$context->instanceid] = $context;
     $ACCESSLIB_PRIVATE->contextsbyid[$context->id] = $context;
 }
diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index ebf30f3799..255f0b90f1 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -5782,21 +5782,21 @@ function forum_add_user_default_subscriptions($userid, $context) {
     switch ($context->contextlevel) {
 
         case CONTEXT_SYSTEM:   // For the whole site
-             if ($courses = $DB->get_records('course')) {
-                 foreach ($courses as $course) {
-                     $subcontext = get_context_instance(CONTEXT_COURSE, $course->id);
-                     forum_add_user_default_subscriptions($userid, $subcontext);
-                 }
+             $rs = $DB->get_recordset('course',null,'','id');
+             foreach ($rs as $course) {
+                 $subcontext = get_context_instance(CONTEXT_COURSE, $course->id);
+                 forum_add_user_default_subscriptions($userid, $subcontext);
              }
+             $rs->close();
              break;
 
         case CONTEXT_COURSECAT:   // For a whole category
-             if ($courses = $DB->get_records('course', array('category' => $context->instanceid))) {
-                 foreach ($courses as $course) {
-                     $subcontext = get_context_instance(CONTEXT_COURSE, $course->id);
-                     forum_add_user_default_subscriptions($userid, $subcontext);
-                 }
+             $rs = $DB->get_recordset('course', array('category' => $context->instanceid),'','id');
+             foreach ($rs as $course) {
+                 $subcontext = get_context_instance(CONTEXT_COURSE, $course->id);
+                 forum_add_user_default_subscriptions($userid, $subcontext);
              }
+             $rs->close();
              if ($categories = $DB->get_records('course_categories', array('parent' => $context->instanceid))) {
                  foreach ($categories as $category) {
                      $subcontext = get_context_instance(CONTEXT_COURSECAT, $category->id);