diff --git a/extensions/debug/panels/DbPanel.php b/extensions/debug/panels/DbPanel.php
index db20ae22cb..ba68391af3 100644
--- a/extensions/debug/panels/DbPanel.php
+++ b/extensions/debug/panels/DbPanel.php
@@ -86,7 +86,7 @@ class DbPanel extends Panel
     protected function calculateTimings()
     {
         if ($this->_timings === null) {
-            $this->_timings = Yii::$app->getLog()->calculateTimings($this->data['messages']);
+            $this->_timings = Yii::getLogger()->calculateTimings($this->data['messages']);
         }
 
         return $this->_timings;
diff --git a/extensions/debug/panels/ProfilingPanel.php b/extensions/debug/panels/ProfilingPanel.php
index 33f698413d..635f4f854e 100644
--- a/extensions/debug/panels/ProfilingPanel.php
+++ b/extensions/debug/panels/ProfilingPanel.php
@@ -85,7 +85,7 @@ class ProfilingPanel extends Panel
     {
         if ($this->_models === null) {
             $this->_models = [];
-            $timings = Yii::$app->getLog()->calculateTimings($this->data['messages']);
+            $timings = Yii::getLogger()->calculateTimings($this->data['messages']);
 
             foreach ($timings as $seq => $profileTiming) {
                 $this->_models[] = 	[
diff --git a/framework/BaseYii.php b/framework/BaseYii.php
index 5a1e8174d6..bfe0240b77 100644
--- a/framework/BaseYii.php
+++ b/framework/BaseYii.php
@@ -348,6 +348,29 @@ class BaseYii
         }
     }
 
+    private static $_logger;
+    
+    /**
+     * @return Logger message logger
+     */
+    public static function getLogger()
+    {
+        if (self::$_logger !== null) {
+            return self::$_logger;
+        } else {
+            return self::$_logger = static::createObject('yii\log\Logger');
+        }
+    }
+
+    /**
+     * Sets the logger object.
+     * @param Logger $logger the logger object.
+     */
+    public static function setLogger($logger)
+    {
+        self::$_logger = $logger;
+    }
+
     /**
      * Logs a trace message.
      * Trace messages are logged mainly for development purpose to see
@@ -358,7 +381,7 @@ class BaseYii
     public static function trace($message, $category = 'application')
     {
         if (YII_DEBUG) {
-            static::$app->getLog()->log($message, Logger::LEVEL_TRACE, $category);
+            static::getLogger()->log($message, Logger::LEVEL_TRACE, $category);
         }
     }
 
@@ -371,7 +394,7 @@ class BaseYii
      */
     public static function error($message, $category = 'application')
     {
-        static::$app->getLog()->log($message, Logger::LEVEL_ERROR, $category);
+        static::getLogger()->log($message, Logger::LEVEL_ERROR, $category);
     }
 
     /**
@@ -383,7 +406,7 @@ class BaseYii
      */
     public static function warning($message, $category = 'application')
     {
-        static::$app->getLog()->log($message, Logger::LEVEL_WARNING, $category);
+        static::getLogger()->log($message, Logger::LEVEL_WARNING, $category);
     }
 
     /**
@@ -395,7 +418,7 @@ class BaseYii
      */
     public static function info($message, $category = 'application')
     {
-        static::$app->getLog()->log($message, Logger::LEVEL_INFO, $category);
+        static::getLogger()->log($message, Logger::LEVEL_INFO, $category);
     }
 
     /**
@@ -417,7 +440,7 @@ class BaseYii
      */
     public static function beginProfile($token, $category = 'application')
     {
-        static::$app->getLog()->log($token, Logger::LEVEL_PROFILE_BEGIN, $category);
+        static::getLogger()->log($token, Logger::LEVEL_PROFILE_BEGIN, $category);
     }
 
     /**
@@ -429,7 +452,7 @@ class BaseYii
      */
     public static function endProfile($token, $category = 'application')
     {
-        static::$app->getLog()->log($token, Logger::LEVEL_PROFILE_END, $category);
+        static::getLogger()->log($token, Logger::LEVEL_PROFILE_END, $category);
     }
 
     /**
diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index d8d92ebfcf..f8df6ae733 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -259,6 +259,7 @@ Yii Framework 2 Change Log
 - Chg: The signature of `Yii::createObject()` is changed. Constructor parameters must be passed as the second parameter. (qiangxue)
 - Chg: `Yii::$objectConfig` is removed. You should use `Yii::$container->set()` to configure default settings of classes. (qiangxue)
 - Chg: Removed `yii\grid\Column::getDataCellContent()` and renamed `yii\grid\DataColumn::getDataCellContent()` to `yii\grid\DataColumn::getDataCellValue()` (cebe)
+- Chg: `yii\log\Logger` is split into `yii\log\Logger` and `yii\log\Dispatcher`. (qiangxue)
 - New #66: [Auth client library](https://github.com/yiisoft/yii2-authclient) OpenId, OAuth1, OAuth2 clients (klimov-paul)
 - New #503: Added `yii\di\Container` and `yii\di\ServiceLocator` (qiangxue)
 - New #706: Added `yii\widgets\Pjax` and enhanced `GridView` to work with `Pjax` to support AJAX-update (qiangxue)
diff --git a/framework/base/Application.php b/framework/base/Application.php
index 11a08b2773..506e19cfab 100644
--- a/framework/base/Application.php
+++ b/framework/base/Application.php
@@ -23,7 +23,7 @@ use yii\web\HttpException;
  * @property ErrorHandler $errorHandler The error handler application component. This property is read-only.
  * @property \yii\base\Formatter $formatter The formatter application component. This property is read-only.
  * @property \yii\i18n\I18N $i18n The internationalization component. This property is read-only.
- * @property \yii\log\Logger $log The log component. This property is read-only.
+ * @property \yii\log\Dispatcher $log The log dispatcher component. This property is read-only.
  * @property \yii\mail\MailerInterface $mail The mailer interface. This property is read-only.
  * @property \yii\web\Request|\yii\console\Request $request The request component. This property is read-only.
  * @property string $runtimePath The directory that stores runtime files. Defaults to the "runtime"
@@ -415,8 +415,8 @@ abstract class Application extends Module
     }
 
     /**
-     * Returns the log component.
-     * @return \yii\log\Logger the log component
+     * Returns the log dispatcher component.
+     * @return \yii\log\Dispatcher the log dispatcher component
      */
     public function getLog()
     {
@@ -512,7 +512,7 @@ abstract class Application extends Module
     public function coreComponents()
     {
         return [
-            'log' => ['class' => 'yii\log\Logger'],
+            'log' => ['class' => 'yii\log\Dispatcher'],
             'errorHandler' => ['class' => 'yii\base\ErrorHandler'],
             'formatter' => ['class' => 'yii\base\Formatter'],
             'i18n' => ['class' => 'yii\i18n\I18N'],
diff --git a/framework/log/Dispatcher.php b/framework/log/Dispatcher.php
new file mode 100644
index 0000000000..f4130535fd
--- /dev/null
+++ b/framework/log/Dispatcher.php
@@ -0,0 +1,135 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\log;
+
+use Yii;
+use yii\base\Component;
+
+/**
+ * Dispatcher manages a set of [[Target|log targets]].
+ *
+ * Dispatcher implements [[dispatch()]] that forwards the log messages from [[Logger]] to
+ * the registered log [[targets]].
+ *
+ * Dispatcher is registered as a core application component and can be accessed using `Yii::$app->log`.
+ *
+ * You may configure the targets in application configuration, like the following:
+ *
+ * ~~~
+ * [
+ *     'components' => [
+ *         'log' => [
+ *             'targets' => [
+ *                 'file' => [
+ *                     'class' => 'yii\log\FileTarget',
+ *                     'levels' => ['trace', 'info'],
+ *                     'categories' => ['yii\*'],
+ *                 ],
+ *                 'email' => [
+ *                     'class' => 'yii\log\EmailTarget',
+ *                     'levels' => ['error', 'warning'],
+ *                     'message' => [
+ *                         'to' => 'admin@example.com',
+ *                     ],
+ *                 ],
+ *             ],
+ *         ],
+ *     ],
+ * ]
+ * ~~~
+ *
+ * Each log target can have a name and can be referenced via the [[targets]] property
+ * as follows:
+ *
+ * ~~~
+ * Yii::$app->log->targets['file']->enabled = false;
+ * ~~~
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Dispatcher extends Component
+{
+    /**
+     * @var array|Target[] the log targets. Each array element represents a single [[Target|log target]] instance
+     * or the configuration for creating the log target instance.
+     */
+    public $targets = [];
+
+    /**
+     * Initializes the logger by registering [[flush()]] as a shutdown function.
+     */
+    public function init()
+    {
+        parent::init();
+
+        foreach ($this->targets as $name => $target) {
+            if (!$target instanceof Target) {
+                $this->targets[$name] = Yii::createObject($target);
+            }
+        }
+
+        Yii::getLogger()->dispatcher = $this;
+    }
+
+    /**
+     * @return integer how many application call stacks should be logged together with each message.
+     * This method returns the value of [[Logger::traceLevel]]. Defaults to 0.
+     */
+    public function getTraceLevel()
+    {
+        return Yii::getLogger()->traceLevel;
+    }
+
+    /**
+     * @param integer $value how many application call stacks should be logged together with each message.
+     * This method will set the value of [[Logger::traceLevel]]. If the value is greater than 0,
+     * at most that number of call stacks will be logged. Note that only application call stacks are counted.
+     * Defaults to 0.
+     */
+    public function setTraceLevel($value)
+    {
+        Yii::getLogger()->traceLevel = $value;
+    }
+
+    /**
+     * @return integer how many messages should be logged before they are sent to targets.
+     * This method returns the value of [[Logger::flushInterval]].
+     */
+    public function getFlushInterval()
+    {
+        return Yii::getLogger()->flushInterval;
+    }
+
+    /**
+     * @param integer $value how many messages should be logged before they are sent to targets.
+     * This method will set the value of [[Logger::flushInterval]].
+     * Defaults to 1000, meaning the [[Logger::flush()]] method will be invoked once every 1000 messages logged.
+     * Set this property to be 0 if you don't want to flush messages until the application terminates.
+     * This property mainly affects how much memory will be taken by the logged messages.
+     * A smaller value means less memory, but will increase the execution time due to the overhead of [[Logger::flush()]].
+     */
+    public function setFlushInterval($value)
+    {
+        Yii::getLogger()->flushInterval = $value;
+    }
+
+    /**
+     * Dispatches the logged messages to [[targets]].
+     * @param array $messages the logged messages
+     * @param boolean $final whether this method is called at the end of the current application
+     */
+    public function dispatch($messages, $final)
+    {
+        foreach ($this->targets as $target) {
+            if ($target->enabled) {
+                $target->collect($messages, $final);
+            }
+        }
+    }
+}
diff --git a/framework/log/Logger.php b/framework/log/Logger.php
index b067e39cad..029f474502 100644
--- a/framework/log/Logger.php
+++ b/framework/log/Logger.php
@@ -11,11 +11,11 @@ use Yii;
 use yii\base\Component;
 
 /**
- * Logger records logged messages in memory and sends them to different targets as needed.
+ * Logger records logged messages in memory and sends them to different targets if [[dispatcher]] is set.
  *
- * Logger is registered as a core application component and can be accessed using `Yii::$app->log`.
- * You can call the method [[log()]] to record a single log message. For convenience, a set of shortcut
- * methods are provided for logging messages of various severity levels via the [[Yii]] class:
+ * Logger can be accessed via `Yii::getLogger()`. You can call the method [[log()]] to record a single log message.
+ * For convenience, a set of shortcut methods are provided for logging messages of various severity levels
+ * via the [[Yii]] class:
  *
  * - [[Yii::trace()]]
  * - [[Yii::error()]]
@@ -24,43 +24,8 @@ use yii\base\Component;
  * - [[Yii::beginProfile()]]
  * - [[Yii::endProfile()]]
  *
- * When enough messages are accumulated in the logger, or when the current request finishes,
- * the logged messages will be sent to different [[targets]], such as log files, emails.
- *
- * You may configure the targets in application configuration, like the following:
- *
- * ~~~
- * [
- *     'components' => [
- *         'log' => [
- *             'targets' => [
- *                 'file' => [
- *                     'class' => 'yii\log\FileTarget',
- *                     'levels' => ['trace', 'info'],
- *                     'categories' => ['yii\*'],
- *                 ],
- *                 'email' => [
- *                     'class' => 'yii\log\EmailTarget',
- *                     'levels' => ['error', 'warning'],
- *                     'message' => [
- *                         'to' => 'admin@example.com',
- *                     ],
- *                 ],
- *             ],
- *         ],
- *     ],
- * ]
- * ~~~
- *
- * Each log target can have a name and can be referenced via the [[targets]] property
- * as follows:
- *
- * ~~~
- * Yii::$app->log->targets['file']->enabled = false;
- * ~~~
- *
  * When the application ends or [[flushInterval]] is reached, Logger will call [[flush()]]
- * to send logged messages to different log targets, such as file, email, Web.
+ * to send logged messages to different log targets, such as file, email, Web, with the help of [[dispatcher]].
  *
  * @property array $dbProfiling The first element indicates the number of SQL statements executed, and the
  * second element the total time spent in SQL execution. This property is read-only.
@@ -124,16 +89,6 @@ class Logger extends Component
      * ~~~
      */
     public $messages = [];
-    /**
-     * @var array debug data. This property stores various types of debug data reported at
-     * different instrument places.
-     */
-    public $data = [];
-    /**
-     * @var array|Target[] the log targets. Each array element represents a single [[Target|log target]] instance
-     * or the configuration for creating the log target instance.
-     */
-    public $targets = [];
     /**
      * @var integer how many messages should be logged before they are flushed from memory and sent to targets.
      * Defaults to 1000, meaning the [[flush]] method will be invoked once every 1000 messages logged.
@@ -146,10 +101,13 @@ class Logger extends Component
      * @var integer how much call stack information (file name and line number) should be logged for each message.
      * If it is greater than 0, at most that number of call stacks will be logged. Note that only application
      * call stacks are counted.
-     *
-     * If not set, it will default to 3 when `YII_ENV` is set as "dev", and 0 otherwise.
      */
-    public $traceLevel;
+    public $traceLevel = 0;
+    /**
+     * @var Dispatcher the message dispatcher
+     */
+    public $dispatcher;
+
 
     /**
      * Initializes the logger by registering [[flush()]] as a shutdown function.
@@ -157,14 +115,6 @@ class Logger extends Component
     public function init()
     {
         parent::init();
-        if ($this->traceLevel === null) {
-            $this->traceLevel = YII_ENV_DEV ? 3 : 0;
-        }
-        foreach ($this->targets as $name => $target) {
-            if (!$target instanceof Target) {
-                $this->targets[$name] = Yii::createObject($target);
-            }
-        }
         register_shutdown_function([$this, 'flush'], true);
     }
 
@@ -208,11 +158,8 @@ class Logger extends Component
      */
     public function flush($final = false)
     {
-        /** @var Target $target */
-        foreach ($this->targets as $target) {
-            if ($target->enabled) {
-                $target->collect($this->messages, $final);
-            }
+        if ($this->dispatcher instanceof Dispatcher) {
+            $this->dispatcher->dispatch($this->messages, $final);
         }
         $this->messages = [];
     }