Fixes LoggerSilence#silence threadsafety

- uses instance defined level if no custom local log level defined
- Keeps track of local log level per [ thread + object-instance ]
- prevents memory leakage by removing local level hash key/value on #silence method exit
- avoids the use of Thread local variables

1 files changed, 22 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/logger_silence.rb b/activesupport/lib/active_support/logger_silence.rb
index 7d92256f24..690e5596f7 100644
--- a/activesupport/lib/active_support/logger_silence.rb
+++ b/activesupport/lib/active_support/logger_silence.rb
@@ -1,22 +1,42 @@
 require 'active_support/concern'
 require 'active_support/core_ext/module/attribute_accessors'
+require 'concurrent'
 
 module LoggerSilence
   extend ActiveSupport::Concern
 
   included do
     cattr_accessor :silencer
+    attr_reader :local_levels
     self.silencer = true
   end
 
+  def after_initialize
+    @local_levels = Concurrent::Map.new(:initial_capacity => 2)
+  end
+
+  def local_log_id
+    Thread.current.__id__
+  end
+
+  def level
+    local_levels[local_log_id] || super
+  end
+
   # Silences the logger for the duration of the block.
   def silence(temporary_level = Logger::ERROR)
     if silencer
       begin
-        old_logger_level, self.level = level, temporary_level
+        old_local_level            = local_levels[local_log_id]
+        local_levels[local_log_id] = temporary_level
+
         yield self
       ensure
-        self.level = old_logger_level
+        if old_local_level
+          local_levels[local_log_id] = old_local_level
+        else
+          local_levels.delete(local_log_id)
+        end
       end
     else
       yield self