From 3da671649f0a2f91aa4a061b9bc6fd637db88604 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Burnichon?= <bburnichon@alchemy.fr>
Date: Fri, 5 Jun 2015 14:22:19 +0200
Subject: [PATCH] When retrieving data from memcache, invalid data is sometimes
 retrieved.

Because of highly concurrent accesses to cache layer, calling isset/get can sometimes fail.

To avoid this, a callback function can be used in memcached driver but it is maintained by doctrine/cache.
To prevent error, check whether returned value is of proper type.
---
 lib/classes/databox/field.php | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/lib/classes/databox/field.php b/lib/classes/databox/field.php
index dede353495..78c8826cf6 100644
--- a/lib/classes/databox/field.php
+++ b/lib/classes/databox/field.php
@@ -28,6 +28,9 @@ class databox_field implements cache_cacheableInterface
 {
     protected $id;
 
+    /** @var Application  */
+    protected $app;
+
     /**
      * @var databox
      */
@@ -208,17 +211,22 @@ class databox_field implements cache_cacheableInterface
     {
         $cache_key = 'field_' . $id;
         $instance_id = $databox->get_sbas_id() . '_' . $id;
-        if ( ! isset(self::$_instance[$instance_id]) || (self::$_instance[$instance_id] instanceof self) === false) {
+        if (! isset(self::$_instance[$instance_id])) {
             try {
-                self::$_instance[$instance_id] = $databox->get_data_from_cache($cache_key);
+                $field = $databox->get_data_from_cache($cache_key);
+                if (!$field instanceof self) {
+                    trigger_error('Cache type returned mismatch', E_WARNING);
+                    throw new \Exception('Retrieved $field value is invalid');
+                }
             } catch (\Exception $e) {
-                self::$_instance[$instance_id] = new self($app, $databox, $id);
-                $databox->set_data_to_cache(self::$_instance[$instance_id], $cache_key);
+                $field = new self($app, $databox, $id);
+                $databox->set_data_to_cache($field, $cache_key);
             }
+            self::$_instance[$instance_id] = $field;
         }
-        self::$_instance[$instance_id]->app = $app;
-
-        return self::$_instance[$instance_id];
+        $field =& self::$_instance[$instance_id];
+        $field->app = $app;
+        return $field;
     }
 
     public function hydrate(Application $app)