MDL-56273 cache: Ensure requirements are met for cache stores.

Ensure that the cache store requirements are met prior to attempting to instantiate a class. Many of the constructors create connections to external services requiring the installation and availability of classes that are specified in are_requirements_met(). If they are not checked properly you end up with PHP Fatal errors rather than falling back to a different store that is capabable without the the extra classes loaded.
mgleeson · Oct 31, 2016 · f9599c7 · f9599c7
1 parent a169739
commit f9599c7
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Showing 3 changed files with 21 additions and 12 deletions.
diff --git a/cache/classes/factory.php b/cache/classes/factory.php
@@ -277,6 +277,9 @@ public function create_store_from_config($name, array $details, cache_definition
         if (!array_key_exists($name, $this->stores)) {
             // Properties: name, plugin, configuration, class.
             $class = $details['class'];
+            if (!$class::are_requirements_met()) {
+                return false;
+            }
             $store = new $class($details['name'], $details['configuration']);
             $this->stores[$name] = $store;
         }

diff --git a/cache/classes/helper.php b/cache/classes/helper.php
@@ -502,15 +502,18 @@ public static function purge_store($storename, cache_config $config = null) {
         $store = $stores[$storename];
         $class = $store['class'];
 
+
+        // We check are_requirements_met although we expect is_ready is going to check as well.
+        if (!$class::are_requirements_met()) {
+            return false;
+        }
         // Found the store: is it ready?
         /* @var cache_store $instance */
         $instance = new $class($store['name'], $store['configuration']);
-        // We check are_requirements_met although we expect is_ready is going to check as well.
-        if (!$instance::are_requirements_met() || !$instance->is_ready()) {
+        if (!$instance->is_ready()) {
             unset($instance);
             return false;
         }
-
         foreach ($config->get_definitions_by_store($storename) as $id => $definition) {
             $definition = cache_definition::load($id, $definition);
             $definitioninstance = clone($instance);

diff --git a/cache/locallib.php b/cache/locallib.php
@@ -684,33 +684,36 @@ public static function get_store_instance_summaries() {
         $locks = $instance->get_locks();
         foreach ($stores as $name => $details) {
             $class = $details['class'];
-            $store = new $class($details['name'], $details['configuration']);
+            $store = false;
+            if ($class::are_requirements_met()) {
+                $store = new $class($details['name'], $details['configuration']);
+            }
             $lock = (isset($details['lock'])) ? $locks[$details['lock']] : $instance->get_default_lock();
             $record = array(
                 'name' => $name,
                 'plugin' => $details['plugin'],
                 'default' => $details['default'],
-                'isready' => $store->is_ready(),
+                'isready' => $store ? $store->is_ready() : false,
                 'requirementsmet' => $class::are_requirements_met(),
                 'mappings' => 0,
                 'lock' => $lock,
                 'modes' => array(
                     cache_store::MODE_APPLICATION =>
-                        ($store->get_supported_modes($return) & cache_store::MODE_APPLICATION) == cache_store::MODE_APPLICATION,
+                        ($class::get_supported_modes($return) & cache_store::MODE_APPLICATION) == cache_store::MODE_APPLICATION,
                     cache_store::MODE_SESSION =>
-                        ($store->get_supported_modes($return) & cache_store::MODE_SESSION) == cache_store::MODE_SESSION,
+                        ($class::get_supported_modes($return) & cache_store::MODE_SESSION) == cache_store::MODE_SESSION,
                     cache_store::MODE_REQUEST =>
-                        ($store->get_supported_modes($return) & cache_store::MODE_REQUEST) == cache_store::MODE_REQUEST,
+                        ($class::get_supported_modes($return) & cache_store::MODE_REQUEST) == cache_store::MODE_REQUEST,
                 ),
                 'supports' => array(
-                    'multipleidentifiers' => $store->supports_multiple_identifiers(),
-                    'dataguarantee' => $store->supports_data_guarantee(),
-                    'nativettl' => $store->supports_native_ttl(),
+                    'multipleidentifiers' => $store ? $store->supports_multiple_identifiers() : false,
+                    'dataguarantee' => $store ? $store->supports_data_guarantee() : false,
+                    'nativettl' => $store ? $store->supports_native_ttl() : false,
                     'nativelocking' => ($store instanceof cache_is_lockable),
                     'keyawareness' => ($store instanceof cache_is_key_aware),
                     'searchable' => ($store instanceof cache_is_searchable)
                 ),
-                'warnings' => $store->get_warnings()
+                'warnings' => $store ? $store->get_warnings() : array()
             );
             if (empty($details['default'])) {
                 $return[$name] = $record;