module ActiveSupport::LoggerThreadSafeLevel

def level
  local_level || super
end

def local_level
  IsolatedExecutionState[local_level_key]
end

def local_level=(level)
  case level
  when Integer
  when Symbol
    level = Logger::Severity.const_get(level.to_s.upcase)
  when nil
  else
    raise ArgumentError, "Invalid log level: #{level.inspect}"
  end
  if level.nil?
    IsolatedExecutionState.delete(local_level_key)
  else
    IsolatedExecutionState[local_level_key] = level
  end
end

def local_level_key
  @local_level_key ||= :"logger_thread_safe_level_#{object_id}"
end

def log_at(level)
  old_local_level, self.local_level = local_level, level
  yield
ensure
  self.local_level = old_local_level
end