1 files changed, 12 insertions, 7 deletions
diff --git a/activesupport/lib/active_support/buffered_logger.rb b/activesupport/lib/active_support/buffered_logger.rb
index cedc1afe7f..6553d72b4f 100644
--- a/activesupport/lib/active_support/buffered_logger.rb
+++ b/activesupport/lib/active_support/buffered_logger.rb
@@ -33,11 +33,10 @@ module ActiveSupport
 
     attr_accessor :level
     attr_reader :auto_flushing
-    attr_reader :buffer
 
     def initialize(log, level = DEBUG)
       @level         = level
-      @buffer        = []
+      @buffer        = {}
       @auto_flushing = 1
       @guard = Mutex.new
 
@@ -60,9 +59,7 @@ module ActiveSupport
       # If a newline is necessary then create a new message ending with a newline.
       # Ensures that the original message is not mutated.
       message = "#{message}\n" unless message[-1] == ?\n
-      @guard.synchronize do
-        buffer << message
-      end
+      buffer << message
       auto_flush
       message
     end
@@ -96,8 +93,8 @@ module ActiveSupport
     def flush
       @guard.synchronize do
         unless buffer.empty?
-          old_buffer    = @buffer
-          @buffer       = []
+          old_buffer = buffer
+          clear_buffer
           @log.write(old_buffer.join)
         end
       end
@@ -113,5 +110,13 @@ module ActiveSupport
       def auto_flush
         flush if buffer.size >= @auto_flushing
       end
+
+      def buffer
+        @buffer[Thread.current] ||= []
+      end
+
+      def clear_buffer
+        @buffer[Thread.current] = []
+      end
   end
 end