Handle Rails logger setting

lib/scout_apm/logging/loggers/capture.rb

@@ -42,20 +42,21 @@ def create_proxy_log_dir!
           Utils.ensure_directory_exists(context.config.value('logs_proxy_log_dir'))
         end
 
-        def add_logging_patches!
+        def add_logging_patches! # rubocop:disable Metrics/AbcSize
+          require_relative './patches/rails_logger' if ::Rails.gem_version < Gem::Version.new('7.1')
           # We can't swap out the logger similar to that of Rails and Sidekiq, as
           # the TaggedLogging logger is dynamically generated.
-          return unless Rails.logger.respond_to?(:tagged)
+          return unless ::Rails.logger.respond_to?(:tagged)
 
           ::ActiveSupport::TaggedLogging.prepend(Patches::TaggedLogging)
 
           # Re-extend TaggedLogging to verify the patch is be applied.
           # This appears to be an issue in Ruby 2.7 with the broadcast logger.
           ruby_version = Gem::Version.new(RUBY_VERSION)
           isruby27 = (ruby_version >= Gem::Version.new('2.7') && ruby_version < Gem::Version.new('3.0'))
-          return unless isruby27 && Rails.logger.respond_to?(:broadcasts)
+          return unless isruby27 && ::Rails.logger.respond_to?(:broadcasts)
 
-          Rails.logger.broadcasts.each do |logger|
+          ::Rails.logger.broadcasts.each do |logger|
             logger.extend ::ActiveSupport::TaggedLogging
           end
         end

lib/scout_apm/logging/loggers/patches/rails_logger.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+# A patch to Rails to allow swapping out the logger for the held logger in the proxy.
+module Rails
+  class << self
+    def logger=(new_logger)
+      @logger.tap do |rails_logger|
+        if rails_logger.respond_to?(:is_scout_proxy_logger?)
+          old_logger = rails_logger.instance_variable_get(:@loggers).first
+          rails_logger.swap_scout_loggers!(old_logger, new_logger)
+        else
+          @logger = new_logger
+        end
+      end
+    end
+  end
+end

lib/scout_apm/logging/loggers/proxy.rb

@@ -19,12 +19,19 @@ def add_scout_loggers(logger)
           @loggers << logger
         end
 
-        def remove_scout_loggers(logger)
+        def remove_scout_loggers!(logger)
           @loggers.reject! { |inst_log| inst_log == logger }
 
           @loggers
         end
 
+        def swap_scout_loggers!(old_logger, new_logger)
+          logger_index = @loggers.index(old_logger)
+          return unless logger_index
+
+          @loggers[logger_index] = new_logger
+        end
+
         # We don't want other libraries to change the formatter of the logger we create.
         def formatter=(formatter)
           @loggers.first.formatter = formatter

lib/scout_apm_logging.rb

@@ -18,7 +18,7 @@ module Logging
     if defined?(Rails) && defined?(Rails::Railtie)
       # If we are in a Rails environment, setup the monitor daemon manager.
       class RailTie < ::Rails::Railtie
-        initializer 'scout_apm_logging.monitor' do
+        initializer 'scout_apm_logging.monitor', after: :initialize_logger, before: :initialize_cache do
           context = ScoutApm::Logging::MonitorManager.instance.context
 
           Loggers::Capture.new(context).setup!