diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterLoggersPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterLoggersPass.php
index 1acb15e..65b691d 100644
--- a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterLoggersPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterLoggersPass.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\DependencyInjection\Compiler;
 
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\Reference;
 
@@ -19,7 +20,9 @@ class RegisterLoggersPass implements CompilerPassInterface {
   public function process(ContainerBuilder $container) {
     $definitions = array();
     foreach ($container->findTaggedServiceIds('logger_channel') as $id => $attributes) {
-      $definitions[] = $container->getDefinition($id);
+      $definition = $container->getDefinition($id);
+      $definition->addMethodCall('setRequest', array(new Reference('request', ContainerInterface::IGNORE_ON_INVALID_REFERENCE)));
+      $definitions[] = $definition;
     }
     // Loop through all available logger services (eg dblog, syslog) and add
     // the available logging channels
diff --git a/core/lib/Drupal/Core/Logger/LoggerChannel.php b/core/lib/Drupal/Core/Logger/LoggerChannel.php
index 027309a..9592a4f 100644
--- a/core/lib/Drupal/Core/Logger/LoggerChannel.php
+++ b/core/lib/Drupal/Core/Logger/LoggerChannel.php
@@ -57,18 +57,26 @@ public function __construct($channel = 'system') {
    * {@inheritdoc}
    */
   public function log($level, $message, array $context = array()) {
-    // @todo Retrieve from request once https://drupal.org/node/1890878 is in.
-    global $user;
+    // Merge in defaults.
     $context += array(
       'type' => $this->channel,
       'link' => '',
-      'user' => $user,
-      'uid' => isset($user->uid) ? $user->uid : 0,
-      'request_uri' => $this->request->server->get('REQUEST_URI', ''),
-      'referer' => $this->request->server->get('HTTP_REFERER', ''),
-      'ip' => $this->request->getClientIP(),
+      'user' => NULL,
+      'uid' => 0,
+      'request_uri' => '',
+      'referer' => '',
+      'ip' => '',
       'timestamp' => time(),
     );
+    // Some context values are only available when in a request context.
+    if ($this->request) {
+      $context['user'] = $this->request->attributes->get('account');
+      $context['uid'] = isset($context['user']) ? $context['user']->id() : 0;
+      $context['request_uri'] = $this->request->getUri();
+      $context['referer'] = $this->request->headers->get('Referer', '');
+      $context['ip'] = $this->request->getClientIP();
+    }
+
     if (is_string($level)) {
       // Convert to integer equivalent for BC and PHP syslog() compatibility.
       $level = $this->mapLevel($level);
@@ -104,6 +112,9 @@ public function addLogger(LoggerInterface $logger, $priority = 0) {
   /**
    * Converts a PSR Log level to a Watchdog log level.
    *
+   * This only exists for BC.
+   * @todo Remove once watchdog() is removed.
+   *
    * @param string $level
    *   A PSR-3 logging level string.
    *
@@ -112,7 +123,8 @@ public function addLogger(LoggerInterface $logger, $priority = 0) {
    */
   protected function mapLevel($level) {
     if (empty($this->levelTranslation)) {
-      // Use PHP constants to keep this unit-testable.
+      // Use PHP constants which are the same with watchdog's ones to keep this
+      // unit-testable.
       $this->levelTranslation = array(
         LogLevel::EMERGENCY => LOG_EMERG,
         LogLevel::ALERT => LOG_ALERT,
diff --git a/core/modules/action/action.services.yml b/core/modules/action/action.services.yml
index 18a114e..709f763 100644
--- a/core/modules/action/action.services.yml
+++ b/core/modules/action/action.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.action:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['action']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/aggregator/aggregator.services.yml b/core/modules/aggregator/aggregator.services.yml
index ac61a29..e1e1372 100644
--- a/core/modules/aggregator/aggregator.services.yml
+++ b/core/modules/aggregator/aggregator.services.yml
@@ -16,7 +16,5 @@ services:
   logger.channel.aggregator:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['aggregator']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/block/custom_block/custom_block.services.yml b/core/modules/block/custom_block/custom_block.services.yml
index 6edab11..faa8500 100644
--- a/core/modules/block/custom_block/custom_block.services.yml
+++ b/core/modules/block/custom_block/custom_block.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.custom_block:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['custom block']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/contact/contact.services.yml b/core/modules/contact/contact.services.yml
index 9601bbb..91d5b68 100644
--- a/core/modules/contact/contact.services.yml
+++ b/core/modules/contact/contact.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.contact:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['contact']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/dblog/lib/Drupal/dblog/Logger/DbLog.php b/core/modules/dblog/lib/Drupal/dblog/Logger/DbLog.php
index 47af121..d15bf0a 100644
--- a/core/modules/dblog/lib/Drupal/dblog/Logger/DbLog.php
+++ b/core/modules/dblog/lib/Drupal/dblog/Logger/DbLog.php
@@ -39,6 +39,8 @@ public function log($level, $message, array $context = array()) {
     // Remove any backtraces since they may contain an unserializable variable.
     unset($context['backtrace']);
 
+    // Convert PSR3-style messages to format_string() style, so they can be
+    // translated too in runtime.
     $this->parseMessagePlaceholders($message, $context);
 
     $this->database
diff --git a/core/modules/file/file.services.yml b/core/modules/file/file.services.yml
index e9f928a..d27b37b 100644
--- a/core/modules/file/file.services.yml
+++ b/core/modules/file/file.services.yml
@@ -5,7 +5,5 @@ services:
   logger.channel.file:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['file']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/filter/filter.services.yml b/core/modules/filter/filter.services.yml
index 4f79be4..62df327 100644
--- a/core/modules/filter/filter.services.yml
+++ b/core/modules/filter/filter.services.yml
@@ -20,7 +20,5 @@ services:
   logger.channel.filter:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['filter']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/forum/forum.services.yml b/core/modules/forum/forum.services.yml
index a9e5ac8..8a7b98a 100644
--- a/core/modules/forum/forum.services.yml
+++ b/core/modules/forum/forum.services.yml
@@ -7,7 +7,5 @@ services:
   logger.channel.forum:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['forum']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/image/image.services.yml b/core/modules/image/image.services.yml
index 6f327f4..a25e448 100644
--- a/core/modules/image/image.services.yml
+++ b/core/modules/image/image.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.image:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['image']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/language/language.services.yml b/core/modules/language/language.services.yml
index b00afe6..caff67d 100644
--- a/core/modules/language/language.services.yml
+++ b/core/modules/language/language.services.yml
@@ -8,7 +8,5 @@ services:
   logger.channel.language:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['language']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/locale/locale.services.yml b/core/modules/locale/locale.services.yml
index d6704d5..b02f963 100644
--- a/core/modules/locale/locale.services.yml
+++ b/core/modules/locale/locale.services.yml
@@ -19,7 +19,5 @@ services:
   logger.channel.locale:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['locale']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/menu/menu.services.yml b/core/modules/menu/menu.services.yml
index 1d9fcc6..bd923a7 100644
--- a/core/modules/menu/menu.services.yml
+++ b/core/modules/menu/menu.services.yml
@@ -10,7 +10,5 @@ services:
   logger.channel.menu:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['menu']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/node/node.services.yml b/core/modules/node/node.services.yml
index 08be04b..f340e46 100644
--- a/core/modules/node/node.services.yml
+++ b/core/modules/node/node.services.yml
@@ -10,14 +10,10 @@ services:
   logger.channel.content:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['content']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.node:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['node']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/picture/picture.services.yml b/core/modules/picture/picture.services.yml
index fb5fd7b..429c5ff 100644
--- a/core/modules/picture/picture.services.yml
+++ b/core/modules/picture/picture.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.picture:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['picture']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/rest/rest.services.yml b/core/modules/rest/rest.services.yml
index b069720..5d4cd0a 100644
--- a/core/modules/rest/rest.services.yml
+++ b/core/modules/rest/rest.services.yml
@@ -23,7 +23,5 @@ services:
   logger.channel.rest:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['rest']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/search/search.services.yml b/core/modules/search/search.services.yml
index 5e09c64..d6a703e 100644
--- a/core/modules/search/search.services.yml
+++ b/core/modules/search/search.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.search:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['search']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/syslog/lib/Drupal/syslog/Logger/SysLog.php b/core/modules/syslog/lib/Drupal/syslog/Logger/SysLog.php
index 48b4d80..87dd173 100644
--- a/core/modules/syslog/lib/Drupal/syslog/Logger/SysLog.php
+++ b/core/modules/syslog/lib/Drupal/syslog/Logger/SysLog.php
@@ -42,15 +42,9 @@ public function __construct(ConfigFactory $config_factory) {
    */
   public function log($level, $message, array $context = array()) {
     global $base_url;
-    $variables = array();
+
     // Populate the $context['variables'] with the message placeholders.
     $this->parseMessagePlaceholders($message, $context);
-    foreach ($context['variables'] as $key => $variable) {
-      // A message placeholder will be in format_string() style after parsing.
-      if (strpos($key, '@') === 0 || strpos($key, '%') === 0 || strpos($key, '!') === 0) {
-        $variables[$key] = $variable;
-      }
-    }
 
     $entry = strtr($this->config->get('format'), array(
       '!base_url' => $base_url,
@@ -61,7 +55,7 @@ public function log($level, $message, array $context = array()) {
       '!referer' => $context['referer'],
       '!uid' => $context['uid'],
       '!link' => strip_tags($context['link']),
-      '!message' => strip_tags(empty($variables) ? $message : strtr($message, $variables)),
+      '!message' => strip_tags(empty($context['variables']) ? $message : strtr($message, $context['variables'])),
     ));
 
     syslog($level, $entry);
diff --git a/core/modules/system/system.services.yml b/core/modules/system/system.services.yml
index cf9a261..979177c 100644
--- a/core/modules/system/system.services.yml
+++ b/core/modules/system/system.services.yml
@@ -20,70 +20,55 @@ services:
   logger.channel.access_denied:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['access denied']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.ajax:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['ajax']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.cron:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['cron']
-    calls:
-      - [setRequest, ['@?request']]
+    tags:
+      - { name: logger_channel }
+  logger.channel.debug:
+    class: Drupal\Core\Logger\LoggerChannel
+    arguments: ['debug']
     tags:
       - { name: logger_channel }
   logger.channel.file_system:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['file system']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.form:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['form']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.mail:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['mail']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.theme:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['theme']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.page_not_found:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['page not found']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.php:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['php']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
   logger.channel.security:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['security']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/taxonomy/taxonomy.services.yml b/core/modules/taxonomy/taxonomy.services.yml
index ecceb76..036cf27 100644
--- a/core/modules/taxonomy/taxonomy.services.yml
+++ b/core/modules/taxonomy/taxonomy.services.yml
@@ -7,7 +7,5 @@ services:
   logger.channel.taxonomy:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['taxonomy']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/tracker/tracker.services.yml b/core/modules/tracker/tracker.services.yml
index f14e154..a2930d0 100644
--- a/core/modules/tracker/tracker.services.yml
+++ b/core/modules/tracker/tracker.services.yml
@@ -2,7 +2,5 @@ services:
   logger.channel.tracker:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['tracker']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/user/user.services.yml b/core/modules/user/user.services.yml
index 3504f21..df8870c 100644
--- a/core/modules/user/user.services.yml
+++ b/core/modules/user/user.services.yml
@@ -28,7 +28,5 @@ services:
   logger.channel.user:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['user']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }
diff --git a/core/modules/views/views.services.yml b/core/modules/views/views.services.yml
index 47fd2bb..bc55ea5 100644
--- a/core/modules/views/views.services.yml
+++ b/core/modules/views/views.services.yml
@@ -93,7 +93,5 @@ services:
   logger.channel.views:
     class: Drupal\Core\Logger\LoggerChannel
     arguments: ['views']
-    calls:
-      - [setRequest, ['@?request']]
     tags:
       - { name: logger_channel }