BroadcastLogger#formatter is its first logger's formatter

There is no practical value in BroadcastLogger storing its own copy of
the formatter. In all observed cases, it is assigned to the value of the
initial Logger, and it is never used by BroadcastLogger.

activesupport/lib/active_support/broadcast_logger.rb

@@ -76,7 +76,6 @@ class BroadcastLogger
 
     # Returns all the logger that are part of this broadcast.
     attr_reader :broadcasts
-    attr_reader :formatter
     attr_accessor :progname
 
     def initialize(*loggers)
@@ -110,6 +109,7 @@ def stop_broadcasting_to(logger)
       << log add debug info warn error fatal unknown
       debug! info! warn! error! fatal!
       level= sev_threshold= local_level local_level= close
+      formatter formatter=
     ]
     LOGGER_METHODS.each do |method|
       class_eval <<-RUBY, __FILE__, __LINE__ + 1
@@ -124,12 +124,6 @@ def level
       @broadcasts.map(&:level).min
     end
 
-    def formatter=(formatter)
-      dispatch(:formatter=, formatter)
-
-      @formatter = formatter
-    end
-
     # +True+ if the log level allows entries with severity Logger::DEBUG to be written
     # to at least one broadcast. +False+ otherwise.
     def debug?
@@ -163,7 +157,6 @@ def fatal?
     def initialize_copy(other)
       @broadcasts = []
       @progname = other.progname.dup
-      @formatter = other.formatter.dup
 
       broadcast_to(*other.broadcasts.map(&:dup))
     end

railties/lib/rails/application/bootstrap.rb

@@ -60,9 +60,7 @@ module Bootstrap
           end
         else
           Rails.logger.level = ActiveSupport::Logger.const_get(config.log_level.to_s.upcase)
-          broadcast_logger = ActiveSupport::BroadcastLogger.new(Rails.logger)
-          broadcast_logger.formatter = Rails.logger.formatter
-          Rails.logger = broadcast_logger
+          Rails.logger = ActiveSupport::BroadcastLogger.new(Rails.logger)
         end
       end