MDL-42192 accesslib: Cache capabilities list

With thanks to Andrew Nicols <andrew@nicols.co.uk> for some ammendments.

lang/en/cache.php

@@ -37,6 +37,7 @@
 $string['cacheadmin'] = 'Cache administration';
 $string['cacheconfig'] = 'Configuration';
 $string['cachedef_calendar_subscriptions'] = 'Calendar subscriptions';
+$string['cachedef_capabilities'] = 'System capabilities list';
 $string['cachedef_config'] = 'Config settings';
 $string['cachedef_coursecat'] = 'Course categories lists for particular user';
 $string['cachedef_coursecatrecords'] = 'Course categories records';

lib/accesslib.php

@@ -203,7 +203,6 @@
 $ACCESSLIB_PRIVATE->dirtycontexts    = null;    // Dirty contexts cache, loaded from DB once per page
 $ACCESSLIB_PRIVATE->accessdatabyuser = array(); // Holds the cache of $accessdata structure for users (including $USER)
 $ACCESSLIB_PRIVATE->rolepermissions  = array(); // role permissions cache - helps a lot with mem usage
-$ACCESSLIB_PRIVATE->capabilities     = null;    // detailed information about the capabilities
 
 /**
  * Clears accesslib's private caches. ONLY BE USED BY UNIT TESTS
@@ -241,7 +240,6 @@ function accesslib_clear_all_caches($resetcontexts) {
     $ACCESSLIB_PRIVATE->dirtycontexts    = null;
     $ACCESSLIB_PRIVATE->accessdatabyuser = array();
     $ACCESSLIB_PRIVATE->rolepermissions  = array();
-    $ACCESSLIB_PRIVATE->capabilities     = null;
 
     if ($resetcontexts) {
         context_helper::reset_caches();
@@ -2532,7 +2530,14 @@ function load_capability_def($component) {
  */
 function get_cached_capabilities($component = 'moodle') {
     global $DB;
-    return $DB->get_records('capabilities', array('component'=>$component));
+    $caps = get_all_capabilities();
+    $componentcaps = array();
+    foreach ($caps as $cap) {
+        if ($cap['component'] == $component) {
+            $componentcaps[] = (object) $cap;
+        }
+    }
+    return $componentcaps;
 }
 
 /**
@@ -2551,12 +2556,12 @@ function get_default_capabilities($archetype) {
     $alldefs = array();
     $defaults = array();
     $components = array();
-    $allcaps = $DB->get_records('capabilities');
+    $allcaps = get_all_capabilities();
 
     foreach ($allcaps as $cap) {
-        if (!in_array($cap->component, $components)) {
-            $components[] = $cap->component;
-            $alldefs = array_merge($alldefs, load_capability_def($cap->component));
+        if (!in_array($cap['component'], $components)) {
+            $components[] = $cap['component'];
+            $alldefs = array_merge($alldefs, load_capability_def($cap['component']));
         }
     }
     foreach($alldefs as $name=>$def) {
@@ -2703,6 +2708,10 @@ function update_capabilities($component = 'moodle') {
         }
     }
 
+    // It is possible somebody directly modified the DB (according to accesslib_test anyway).
+    // So ensure our updating is based on fresh data.
+    cache::make('core', 'capabilities')->delete('core_capabilities');
+
     $cachedcaps = get_cached_capabilities($component);
     if ($cachedcaps) {
         foreach ($cachedcaps as $cachedcap) {
@@ -2738,6 +2747,9 @@ function update_capabilities($component = 'moodle') {
         }
     }
 
+    // Flush the cached again, as we have changed DB.
+    cache::make('core', 'capabilities')->delete('core_capabilities');
+
     // Are there new capabilities in the file definition?
     $newcaps = array();
 
@@ -2788,6 +2800,9 @@ function update_capabilities($component = 'moodle') {
     // reset static caches
     accesslib_clear_all_caches(false);
 
+    // Flush the cached again, as we have changed DB.
+    cache::make('core', 'capabilities')->delete('core_capabilities');
+
     return true;
 }
 
@@ -2826,6 +2841,9 @@ function capabilities_cleanup($component, $newcapdef = null) {
             } // End if.
         }
     }
+    if ($removedcount) {
+        cache::make('core', 'capabilities')->delete('core_capabilities');
+    }
     return $removedcount;
 }
 
@@ -2946,21 +2964,33 @@ function is_inside_frontpage(context $context) {
 function get_capability_info($capabilityname) {
     global $ACCESSLIB_PRIVATE, $DB; // one request per page only
 
-    //TODO: MUC - this could be cached in shared memory, it would eliminate 1 query per page
+    $caps = get_all_capabilities();
 
-    if (empty($ACCESSLIB_PRIVATE->capabilities)) {
-        $ACCESSLIB_PRIVATE->capabilities = array();
-        $caps = $DB->get_records('capabilities', array(), '', 'id, name, captype, riskbitmask');
-        foreach ($caps as $cap) {
-            $capname = $cap->name;
-            unset($cap->id);
-            unset($cap->name);
-            $cap->riskbitmask = (int)$cap->riskbitmask;
-            $ACCESSLIB_PRIVATE->capabilities[$capname] = $cap;
-        }
+    if (!isset($caps[$capabilityname])) {
+        return null;
     }
 
-    return isset($ACCESSLIB_PRIVATE->capabilities[$capabilityname]) ? $ACCESSLIB_PRIVATE->capabilities[$capabilityname] : null;
+    return (object) $caps[$capabilityname];
+}
+
+/**
+ * Returns all capabilitiy records, preferably from MUC and not database.
+ *
+ * @return array All capability records
+ */
+function get_all_capabilities() {
+    global $DB;
+    $cache = cache::make('core', 'capabilities');
+    if (!$allcaps = $cache->get('core_capabilities')) {
+        $allcaps = $DB->get_records('capabilities', null, '', 'name as uniquename, *');
+        foreach ($allcaps as $k => $v) {
+            unset($v->uniquename);
+            $v->riskbitmask = (int) $v->riskbitmask;
+            $allcaps[$k] = (array) $v;
+        }
+        $cache->set('core_capabilities', $allcaps);
+    }
+    return $allcaps;
 }
 
 /**

lib/db/caches.php

@@ -126,6 +126,16 @@
         'staticacceleration' => true,
     ),
 
+    // Cache the capabilities list DB table. See get_all_capabilities in accesslib.
+    'capabilities' => array(
+        'mode' => cache_store::MODE_APPLICATION,
+        'simplekeys' => true,
+        'simpledata' => true,
+        'staticacceleration' => true,
+        'staticaccelerationsize' => 1,
+        'ttl' => 3600, // Just in case.
+    ),
+
     // YUI Module cache.
     // This stores the YUI module metadata for Shifted YUI modules in Moodle.
     'yuimodules' => array(

lib/tests/accesslib_test.php

@@ -67,6 +67,20 @@ public function test_accesslib_clear_all_caches() {
         $this->assertEmpty($ACCESSLIB_PRIVATE->accessdatabyuser);
     }
 
+    /**
+     * Check modifying capability record is not exposed to other code.
+     */
+    public function test_capabilities_mutation() {
+        $oldcap = get_capability_info('moodle/site:config');
+        $cap = get_capability_info('moodle/site:config');
+        unset($cap->name);
+        $newcap = get_capability_info('moodle/site:config');
+
+        $this->assertFalse(isset($cap->name));
+        $this->assertTrue(isset($newcap->name));
+        $this->assertTrue(isset($oldcap->name));
+    }
+
     /**
      * Test getting of role access
      */