Issue #94: Added ability for a datasource to have a null cache key, v…

…oiding the caching of the content.

Several methods have been deprecated.
- base::get_content_hash
- base::update_config_hash

backup/moodle2/restore_cms_activity_task.class.php

@@ -39,14 +39,14 @@ class restore_cms_activity_task extends restore_activity_task {
      * Define (add) particular settings this activity can have
      */
     protected function define_my_settings() {
-        // No particular settings for this activity
+        // No particular settings for this activity.
     }
 
     /**
      * Define (add) particular steps this activity can have
      */
     protected function define_my_steps() {
-        // Choice only has one structure step
+        // Choice only has one structure step.
         $this->add_step(new restore_cms_activity_structure_step('cms_structure', 'cms.xml'));
     }
 

classes/customfield/cmsfield_handler.php

@@ -108,6 +108,6 @@ protected function clear_configuration_cache() {
         parent::clear_configuration_cache();
         $cmstype = new cms_types($this->get_itemid());
         $fields = new fields($cmstype->get_sample_cms());
-        $fields->update_config_hash();
+        $fields->update_config_cache_key();
     }
 }

classes/customfield/cmsuserlist_handler.php

@@ -116,6 +116,6 @@ protected function clear_configuration_cache() {
         parent::clear_configuration_cache();
         $cmstype = new cms_types($this->get_itemid());
         $userlist = new userlist($cmstype->get_sample_cms());
-        $userlist->update_config_hash();
+        $userlist->update_config_cache_key();
     }
 }

classes/helper.php

@@ -44,9 +44,8 @@ class helper {
      * @param string $url
      * @param string $icon
      * @param string $alt
-     * @param string $iconcomponent
+     * @param string|null $iconcomponent
      * @param array  $options
-     *
      * @return string
      */
     public static function format_icon_link(string $url, string $icon, string $alt,

classes/local/datasource/base.php

@@ -42,6 +42,12 @@ abstract class base {
     /** @var array List of datasource class names in use. */
     protected static $datasourceclasses = [];
 
+    /**
+     * @var bool Set to true if the datasource makes use of caching.
+     * Override and set to false in any datasource that is not to be cached.
+     */
+    public static $usecache = true;
+
     /**
      * Create the list of datasources to be used.
      */
@@ -207,12 +213,38 @@ public static function is_optional(): bool {
     }
 
     /**
-     * Pulls data from the datasource.
+     * Constructs the data structure to act as the data source.
      *
      * @return \stdClass
      */
     abstract public function get_data(): \stdClass;
 
+    /**
+     * Constructs the data structure to act as the data source. Uses a cache.
+     *
+     * @return \stdClass
+     * @throws \coding_exception
+     */
+    public function get_cached_data(): \stdClass {
+        if (!static::$usecache) {
+            return $this->get_data();
+        }
+
+        $key = $this->get_full_cache_key();
+
+        if (is_null($key)) {
+            return $this->get_data();
+        }
+
+        $cache = \cache::make('mod_cms', 'cms_content_' . self::get_shortname());
+        $data = $cache->get($key);
+        if ($data === false) {
+            $data = $this->get_data();
+            $cache->set($key, $data);
+        }
+        return $data;
+    }
+
     /**
      * Add fields to the CMS instance form.
      *
@@ -313,21 +345,76 @@ public function set_from_import(\stdClass $data) {
     /**
      * Returns a hash of the content, representing the data stored for the datasource.
      *
-     * @return string
+     * @deprecated
+     * @return string|null
+     * @throws \moodle_exception
      */
-    abstract public function get_content_hash(): string;
+    public function get_content_hash(): ?string {
+        throw new \moodle_exception('This method is deprecated. Use get_instance_cache_key() instead');
+    }
 
     /**
-     * Update the config hash.
+     * Returns the cache key fragment for the instance data.
+     * If null, then caching should be avoided, both here and for the overall instance.
+     *
+     * @return string|null
      */
-    public function update_config_hash() {
+    public function get_instance_cache_key(): ?string {
+        if (!empty($this->cms->get('id'))) {
+            $this->cms->read();
+        }
+        return $this->cms->get_custom_data(self::get_shortname() . 'instancehash') ?? '';
+    }
+
+    /**
+     * Returns the cache key fragment for the config.
+     * If null, then caching should be avoided, both here and for the overall instance.
+     *
+     * @return string|null
+     */
+    public function get_config_cache_key(): ?string {
+        $cmstype = $this->cms->get_type();
+        return $cmstype->get_custom_data(self::get_shortname() . 'confighash') ?? '';
+    }
+
+    /**
+     * Gets the current cache key used for this datasource for this instance. It concatenates the instance and config keys.
+     * If either key is null, then this function returns null.
+     *
+     * @return string|null
+     */
+    public function get_full_cache_key(): ?string {
+        if (!static::$usecache) {
+            return '';
+        }
+        $ikey = $this->get_instance_cache_key();
+        $ckey = $this->get_config_cache_key();
+        if (is_null($ikey) || is_null($ckey)) {
+            return null;
+        }
+        return $ikey . $ckey;
+    }
+
+    /** Updates the config cache key fragment. */
+    public function update_config_cache_key() {
+        // TODO: Switch to revision based hashing?
         $hash = hash(lib::HASH_ALGO, serialize($this->get_for_export()));
         // The config hash is stored with the CMS type.
         $cmstype = $this->cms->get_type();
         $cmstype->set_custom_data(self::get_shortname() . 'confighash', $hash);
         $cmstype->save();
     }
 
+    /**
+     * Update the config hash.
+     *
+     * @deprecated
+     * @throws \moodle_exception
+     */
+    public function update_config_hash() {
+        throw new \moodle_exception('This method is deprecated. Use update_config_cache_key() instead');
+    }
+
     /**
      * Called when deleting a CMS type.
      */

classes/local/datasource/fields.php

@@ -201,7 +201,7 @@ public function set_from_import(\stdClass $data) {
                 }
             }
         }
-        $this->update_config_hash();
+        $this->update_config_cache_key();
     }
 
     /**
@@ -213,8 +213,10 @@ public function set_from_import(\stdClass $data) {
     public function update_instance(\stdClass $instancedata, bool $isnewinstance) {
         // Save the custom field data.
         $this->cfhandler->instance_form_save($instancedata, $isnewinstance);
+
+        // Update the instance cache key.
+        // TODO: Change to use hash of $instancedata?
         $hash = hash(lib::HASH_ALGO, serialize($this->get_data()));
-        // The content hash is stored as a part fo the cms.
         $this->cms->set_custom_data('fieldsinstancehash', $hash);
         $this->cms->save();
     }

classes/local/datasource/images.php

@@ -153,7 +153,7 @@ public function config_on_update($data) {
                 $this->cms->get('typeid')
             );
         }
-        $this->update_config_hash();
+        $this->update_config_cache_key();
     }
 
     /**
@@ -204,15 +204,16 @@ public function set_from_import(\stdClass $data) {
                 $fs->create_file_from_string($filerecord, base64_decode($filedata->content));
             }
         }
+        $this->update_config_cache_key();
     }
 
     /**
-     * Returns a hash of the content, representing the data stored for the datasource.
+     * Returns the cache key for the instance data.
      *
      * @return string
      */
-    public function get_content_hash(): string {
-        // There is no instance specific data, so no content hash is needed.
+    public function get_instance_cache_key(): string {
+        // There is no instance specific data, so key fragment is constant.
         return '';
     }
 

classes/local/datasource/roles.php

@@ -243,7 +243,7 @@ public function config_on_update($data) {
         ];
         $cmstype->set_custom_data('roles_config', $config);
         $cmstype->save();
-        $this->update_config_hash();
+        $this->update_config_cache_key();
     }
 
     /**
@@ -275,16 +275,7 @@ public function set_from_import(\stdClass $data) {
         ];
         $cmstype->set_custom_data('roles_config', $config);
         $cmstype->save();
-    }
-
-    /**
-     * Returns a hash of the content, representing the data stored for the datasource.
-     *
-     * @return string
-     */
-    public function get_content_hash(): string {
-        // Hash is stored in the DB with the cms, so gets returned by cms::get_content_hash().
-        return '';
+        $this->update_config_cache_key();
     }
 
     /**
@@ -314,6 +305,19 @@ function($v) {
         );
     }
 
+    /**
+     * Returns the cache key fragment for the instance data.
+     * If null, then caching should be avoided, both here and for the overall instance.
+     *
+     * @return string|null
+     */
+    public function get_instance_cache_key(): ?string {
+        if (!empty($this->cms->get('id'))) {
+            $this->cms->read();
+        }
+        return $this->cms->get_custom_data('roles_course_role_cache_rev') ?? '';
+    }
+
     /**
      * Called whenever a role assignment has changed in order to update the datasource cache.
      *

classes/local/datasource/site.php

@@ -25,6 +25,10 @@
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class site extends base {
+
+    /** @var bool Set to false when the datasource doees not cache. */
+    public static $usecache = false;
+
     /**
      * Get the display name.
      *
@@ -57,15 +61,4 @@ public function get_data(): \stdClass {
     public static function is_optional(): bool {
         return false;
     }
-
-    /**
-     * Returns a hash of the content, representing the data stored for the datasource.
-     *
-     * @return string
-     */
-    public function get_content_hash(): string {
-        // There is no instance specific data, so no content hash is needed.
-        return '';
-    }
-
 }

classes/local/datasource/userlist.php

@@ -289,9 +289,9 @@ public function update_instance(\stdClass $instancedata, bool $isnewinstance) {
             $this->cms->set_custom_data('userlistinstanceids', $instanceids);
         }
 
-        // Update hash.
+        // Update the instance cache key.
+        // TODO: Change to use $instancedata->data?
         $hash = hash(lib::HASH_ALGO, serialize($this->get_data()));
-        // The content hash is stored as a part fo the cms.
         $this->cms->set_custom_data('userlistinstancehash', $hash);
         $this->cms->save();
     }
@@ -373,7 +373,7 @@ public function config_on_update($data) {
         if (count($categories) === 0) {
             $this->cfhandler->create_category('');
         }
-        $this->update_config_hash();
+        $this->update_config_cache_key();
     }
 
     /**
@@ -417,16 +417,7 @@ public function set_from_import(\stdClass $data) {
                 $field->save();
             }
         }
-    }
-
-    /**
-     * Returns a hash of the content, representing the data stored for the datasource.
-     *
-     * @return string
-     */
-    public function get_content_hash(): string {
-        // Hash is stored in the DB with the cms, so gets returned by cms::get_content_hash().
-        return '';
+        $this->update_config_cache_key();
     }
 
     /**

classes/local/lib.php

@@ -135,7 +135,7 @@ public static function update_instance(\stdClass $instancedata, $mform): bool {
     }
 
     /**
-     * Rest the name field of cms instances.
+     * Reset the name field of cms instances.
      *
      * @param int $typeid
      * @throws \coding_exception

classes/local/model/cms.php

@@ -87,16 +87,35 @@ protected static function define_properties(): array {
      * Includes hashes for the CMS type and the datasources as well, as they
      * contribute to what gets displayed.
      *
+     * @deprecated
      * @return string
+     * @throws \moodle_exception
      */
     public function get_content_hash(): string {
-        $hash = '';
+        throw new \moodle_exception('This method is deprecated. Use get_cache_key instead');
+    }
+
+    /**
+     * Creates and returns a cache key. This key is a hash of the combination of the
+     * datasources, the CMS type and the CMS data.
+     *
+     * @return string|null
+     */
+    public function get_cache_key(): ?string {
+        $key = '';
         foreach (dsbase::get_datasources($this) as $ds) {
-            $hash .= $ds->get_content_hash();
+            $dskey = $ds->get_full_cache_key();
+            if (is_null($dskey)) {
+                return null;
+            }
+            $key .= $dskey;
         }
-        $hash .= hash(lib::HASH_ALGO, serialize($this->to_record()));
-        $hash .= $this->get_type()->get_content_hash();
-        return $hash;
+
+        $key .= serialize($this->get_type()->to_record());
+        $key .= serialize($this->to_record());
+
+        // Return a hash to keep the key length to an acceptable size.
+        return hash(lib::HASH_ALGO, $key);
     }
 
     /**