Fix threading issues with BufferedLogger.

activesupport/lib/active_support/buffered_logger.rb

@@ -25,22 +25,28 @@ module Severity
     # Silences the logger for the duration of the block.
     def silence(temporary_level = ERROR)
       if silencer
+        old_logger_level = @tmp_levels[Thread.current]
         begin
-          old_logger_level, self.level = level, temporary_level
+          @tmp_levels[Thread.current] = temporary_level
           yield self
         ensure
-          self.level = old_logger_level
+          if old_logger_level
+            @tmp_levels[Thread.current] = old_logger_level
+          else
+            @tmp_levels.delete(Thread.current)
+          end
         end
       else
         yield self
       end
     end
 
-    attr_accessor :level
+    attr_writer :level
     attr_reader :auto_flushing
 
     def initialize(log, level = DEBUG)
       @level         = level
+      @tmp_levels    = {}
       @buffer        = Hash.new { |h,k| h[k] = [] }
       @auto_flushing = 1
       @guard = Mutex.new
@@ -62,8 +68,12 @@ def open_log(log, mode)
       end
     end
 
+    def level
+      @tmp_levels[Thread.current] || @level
+    end
+
     def add(severity, message = nil, progname = nil, &block)
-      return if @level > severity
+      return if level > severity
       message = (message || (block && block.call) || progname).to_s
       # If a newline is necessary then create a new message ending with a newline.
       # Ensures that the original message is not mutated.
@@ -84,7 +94,7 @@ def #{severity.downcase}(message = nil, progname = nil, &block) # def debug(mess
         end                                                             # end
 
         def #{severity.downcase}?                                       # def debug?
-          #{severity} >= @level                                         #   DEBUG >= @level
+          #{severity} >= level                                         #   DEBUG >= @level
         end                                                             # end
       EOT
     end
@@ -105,13 +115,15 @@ def auto_flushing=(period)
 
     def flush
       @guard.synchronize do
-        buffer.each do |content|
-          @log.write(content)
-        end
+        write_buffer(buffer)
 
         # Important to do this even if buffer was empty or else @buffer will
         # accumulate empty arrays for each request where nothing was logged.
         clear_buffer
+
+        # Clear buffers associated with dead threads or else spawned threads
+        # that don't call flush will result in a memory leak.
+        flush_dead_buffers
       end
     end
 
@@ -133,5 +145,21 @@ def buffer
       def clear_buffer
         @buffer.delete(Thread.current)
       end
+
+      # Find buffers created by threads that are no longer alive and flush them to the log
+      # in order to prevent memory leaks from spawned threads.
+      def flush_dead_buffers #:nodoc:
+        @buffer.keys.reject{|thread| thread.alive?}.each do |thread|
+          buffer = @buffer[thread]
+          write_buffer(buffer)
+          @buffer.delete(thread)
+        end
+      end
+
+      def write_buffer(buffer)
+        buffer.each do |content|
+          @log.write(content)
+        end
+      end
   end
 end

activesupport/test/buffered_logger_test.rb

@@ -198,4 +198,57 @@ def test_buffer_multibyte
     end
     assert byte_string.include?(BYTE_STRING)
   end
+
+  def test_silence_only_current_thread
+    @logger.auto_flushing = true
+    run_thread_a = false
+
+    a = Thread.new do
+      while !run_thread_a do
+        sleep(0.001)
+      end
+      @logger.info("x")
+      run_thread_a = false
+    end
+
+    @logger.silence do
+      run_thread_a = true
+      @logger.info("a")
+      while run_thread_a do
+        sleep(0.001)
+      end
+    end
+
+    a.join
+
+    assert @output.string.include?("x")
+    assert !@output.string.include?("a")
+  end
+
+  def test_flush_dead_buffers
+    @logger.auto_flushing = false
+
+    a = Thread.new do
+      @logger.info("a")
+    end
+    
+    keep_running = true
+    b = Thread.new do
+      @logger.info("b")
+      while keep_running
+        sleep(0.001)
+      end
+    end
+
+    @logger.info("x")
+    a.join
+    @logger.flush
+
+
+    assert @output.string.include?("x")
+    assert @output.string.include?("a")
+    assert !@output.string.include?("b")
+    
+    keep_running = false
+  end
 end