1 files changed, 55 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/logger_thread_safe_level.rb b/activesupport/lib/active_support/logger_thread_safe_level.rb
new file mode 100644
index 0000000000..f16c90cfc6
--- /dev/null
+++ b/activesupport/lib/active_support/logger_thread_safe_level.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "active_support/concern"
+require "active_support/core_ext/module/attribute_accessors"
+require "concurrent"
+
+module ActiveSupport
+  module LoggerThreadSafeLevel # :nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      cattr_accessor :local_levels, default: Concurrent::Map.new(initial_capacity: 2), instance_accessor: false
+    end
+
+    Logger::Severity.constants.each do |severity|
+      class_eval(<<-EOT, __FILE__, __LINE__ + 1)
+        def #{severity.downcase}?                # def debug?
+          Logger::#{severity} >= level           #   DEBUG >= level
+        end                                      # end
+      EOT
+    end
+
+    def after_initialize
+      ActiveSupport::Deprecation.warn(
+        "Logger don't need to call #after_initialize directly anymore. It will be deprecated without replacement in " \
+        "Rails 6.1."
+      )
+    end
+
+    def local_log_id
+      Thread.current.__id__
+    end
+
+    def local_level
+      self.class.local_levels[local_log_id]
+    end
+
+    def local_level=(level)
+      if level
+        self.class.local_levels[local_log_id] = level
+      else
+        self.class.local_levels.delete(local_log_id)
+      end
+    end
+
+    def level
+      local_level || super
+    end
+
+    def add(severity, message = nil, progname = nil, &block) # :nodoc:
+      return true if @logdev.nil? || (severity || UNKNOWN) < level
+      super
+    end
+  end
+end