MDL-37683 cache: improved indentifier collection and storage

cache/classes/definition.php

@@ -274,12 +274,6 @@ class cache_definition {
      */
     protected $definitionhash = null;
 
-    /**
-     * An identifier to make cache keys predictably unique.
-     * @var string
-     */
-    protected $cacheidentifier = '0';
-
     /**
      * Creates a cache definition given a definition from the cache configuration or from a caches.php file.
      *
@@ -680,15 +674,6 @@ class cache_definition {
         $this->keyprefixmulti = null;
     }
 
-    /**
-     * Sets an identifier for the cache.
-     * This can be used
-     * @param string $identifier
-     */
-    public function set_cache_identifier($identifier) {
-        $this->cacheidentifier = (string)$identifier;
-    }
-
     /**
      * Returns the requirements of this definition as a binary flag.
      * @return int
@@ -739,7 +724,7 @@ class cache_definition {
     public function generate_single_key_prefix() {
         if ($this->keyprefixsingle === null) {
             $this->keyprefixsingle = $this->mode.'/'.$this->component.'/'.$this->area;
-            $this->keyprefixsingle .= '/'.$this->cacheidentifier;
+            $this->keyprefixsingle .= '/'.$this->get_cache_identifier();
             $identifiers = $this->get_identifiers();
             if ($identifiers) {
                 foreach ($identifiers as $key => $value) {
@@ -762,7 +747,7 @@ class cache_definition {
                 'mode' => $this->mode,
                 'component' => $this->component,
                 'area' => $this->area,
-                'siteidentifier' => $this->cacheidentifier
+                'siteidentifier' => $this->get_cache_identifier()
             );
             if (!empty($this->identifiers)) {
                 $identifiers = array();
@@ -802,4 +787,13 @@ class cache_definition {
     public function get_invalidation_events() {
         return $this->invalidationevents;
     }
+
+    /**
+     * Returns a cache identification string.
+     *
+     * @return string A string to be used as part of keys.
+     */
+    protected function get_cache_identifier() {
+        return cache_helper::get_site_identifier();
+    }
 }

cache/classes/factory.php

@@ -204,7 +204,6 @@ class cache_factory {
         // Get the class. Note this is a late static binding so we need to use get_called_class.
         $definition = cache_definition::load_adhoc($mode, $component, $area, $options);
         $config = $this->create_config_instance();
-        $definition->set_cache_identifier($config->get_site_identifier());
         $definition->set_identifiers($identifiers);
         $cache = $this->create_cache($definition, $identifiers);
         if ($definition->should_be_persistent()) {
@@ -392,7 +391,6 @@ class cache_factory {
                 } else {
                     $definition = cache_definition::load($id, $definition, $aggregate);
                 }
-                $definition->set_cache_identifier($instance->get_site_identifier());
             }
             $this->definitions[$id] = $definition;
         }

cache/classes/helper.php

@@ -54,6 +54,13 @@ class cache_helper {
      */
     protected static $instance;
 
+    /**
+     * The site identifier used by the cache.
+     * Set the first time get_site_identifier is called.
+     * @var string
+     */
+    protected static $siteidentifier = null;
+
     /**
      * Returns true if the cache API can be initialised before Moodle has finished initialising itself.
      *
@@ -234,7 +241,6 @@ class cache_helper {
         $factory = cache_factory::instance();
         foreach ($instance->get_definitions() as $name => $definitionarr) {
             $definition = cache_definition::load($name, $definitionarr);
-            $definition->set_cache_identifier($instance->get_site_identifier());
             if ($definition->invalidates_on_event($event)) {
                 // OK at this point we know that the definition has information to invalidate on the event.
                 // There are two routes, either its an application cache in which case we can invalidate it now.
@@ -305,7 +311,6 @@ class cache_helper {
         $factory = cache_factory::instance();
         foreach ($instance->get_definitions() as $name => $definitionarr) {
             $definition = cache_definition::load($name, $definitionarr);
-            $definition->set_cache_identifier($instance->get_site_identifier());
             if ($definition->invalidates_on_event($event)) {
                 // Create the cache.
                 $cache = $factory->create_cache($definition);
@@ -515,4 +520,28 @@ class cache_helper {
         $factory->updating_finished();
         cache_factory::reset();
     }
+
+    /**
+     * Returns the site identifier.
+     *
+     * @return string
+     */
+    public static function get_site_identifier() {
+        if (is_null(self::$siteidentifier)) {
+            $factory = cache_factory::instance();
+            $config = $factory->create_config_instance();
+            self::$siteidentifier = $config->get_site_identifier();
+        }
+        return self::$siteidentifier;
+    }
+
+    /**
+     * Returns the site version.
+     *
+     * @return string
+     */
+    public static function get_site_version() {
+        global $CFG;
+        return (string)$CFG->version;
+    }
 }