Changed the default value of `Cache::keyPrefix` to be null.

framework/CHANGELOG.md

@@ -63,7 +63,7 @@ Yii Framework 2 Change Log
 - Chg: `yii\grid\DataColumn::getDataCellValue()` visibility is now `public` to allow accessing the value from a GridView directly (cebe)
 - Chg: `yii\data\ActiveDataProvider::$query` will not be modified directly with pagination and sorting anymore so it will be reuseable (cebe)
 - Chg: Removed `yii\rest\ActiveController::$transactional` property and connected functionality (samdark)
-
+- Chg: Changed the default value of the `keyPrefix` property of cache components to be null (qiangxue)
 
 2.0.0-beta April 13, 2014
 -------------------------

framework/UPGRADE.md

@@ -29,3 +29,7 @@ Upgrade from Yii 2.0 Beta
   `yii\filters\auth\HttpBearerAuth` authentication method, the value of this parameter will be
   `yii\filters\auth\HttpBearerAuth`. This allows you to differentiate access tokens taken by
   different authentication methods.
+
+* If you are sharing the same cache across different applications, you should configure
+  the `keyPrefix` property of the cache component to use some unique string.
+  Previously, this property was automatically assigned with a unique string.

framework/caching/Cache.php

@@ -7,7 +7,6 @@
 
 namespace yii\caching;
 
-use Yii;
 use yii\base\Component;
 use yii\helpers\StringHelper;
 
@@ -52,10 +51,9 @@ use yii\helpers\StringHelper;
 abstract class Cache extends Component implements \ArrayAccess
 {
     /**
-     * @var string a string prefixed to every cache key so that it is unique. If not set,
-     * it will use a prefix generated from [[\yii\base\Application::id]]. You may set this property to be an empty string
-     * if you don't want to use key prefix. It is recommended that you explicitly set this property to some
-     * static value if the cached data needs to be shared among multiple applications.
+     * @var string a string prefixed to every cache key so that it is unique globally in the whole cache storage.
+     * It is recommended that you set a unique cache key prefix for each application if the same cache
+     * storage is being used by different applications.
      *
      * To ensure interoperability, only alphanumeric characters should be used.
      */
@@ -71,17 +69,6 @@ abstract class Cache extends Component implements \ArrayAccess
      */
     public $serializer;
 
-    /**
-     * Initializes the application component.
-     * This method overrides the parent implementation by setting default cache key prefix.
-     */
-    public function init()
-    {
-        parent::init();
-        if ($this->keyPrefix === null) {
-            $this->keyPrefix = substr(md5(Yii::$app->id), 0, 5);
-        }
-    }
 
     /**
      * Builds a normalized cache key from a given key.

tests/unit/framework/caching/CacheTestCase.php

@@ -58,16 +58,6 @@ abstract class CacheTestCase extends TestCase
         return $cache;
     }
 
-    /**
-     * default value of cache prefix is application id
-     */
-    public function testKeyPrefix()
-    {
-        $cache = $this->getCacheInstance();
-        $this->assertNotNull(\Yii::$app->id);
-        $this->assertNotNull($cache->keyPrefix);
-    }
-
     public function testSet()
     {
         $cache = $this->getCacheInstance();