RailsでLTSV形式でLogを出す

Gemとかあるのかもしれないけど、とりあえず自分で作ったものを使ってる

module Utils
  class FormattedLogger
    class << self
      def create(path, taggers=nil)
        unless File.exist?(File.dirname(path))
          FileUtils.mkdir_p(File.dirname(path))
        end
        logger = Logger.new(path, taggers)
        logger.formatter = proc do |severity, datetime, progname, msg|
          log = []
          log << "pid:#{$PROCESS_ID}"
          log << "level:#{severity}"
          log << "datetime:#{datetime}"

          file_caller = caller.find { |item| item.include?("#{Rails.root}/app") }
          if file_caller.present?
            filename, line_num = file_caller.match(/(?<path>.*):(?<line_num>\d+)/).tap do |path_and_line_num|
              break [
                path_and_line_num['path'].gsub("#{Rails.root}", ''),
                path_and_line_num['line_num']
              ]
            end
            log << "filename:#{filename}"
            log << "line_num:#{line_num}"
          end
          case msg
          when Hash
            msg.each do |key, val|
              log << "#{key}:#{val}"
            end
          else
            msg_divided_uuid = msg.match(/^\[(.*)\](.*)/)
            if msg_divided_uuid
              log << "uuid:#{msg_divided_uuid[1]}"
              log << "message:#{msg_divided_uuid[2].strip}"
            else
              log << "message:#{msg}"
            end
          end
          "#{log.join("\t")}\n"
        end
        ActiveSupport::TaggedLogging.new(logger)
      rescue StandardError
        logger = ActiveSupport::TaggedLogging.new(ActiveSupport::BufferedLogger.new(STDERR))
        logger.level = ActiveSupport::BufferedLogger::WARN
        logger.warn(
          "Rails Error: Unable to access log file. Please ensure that #{path} exists and is chmod 0666. " \
          'The log level has been raised to WARN and the output directed to STDERR until the problem is fixed.'
        )
        logger
      end
    end
  end
end

lib配下に置くと、 config/application.rb の読み込み中だとまだ読み込まれていないみたいなので、下記のような記載が必要

require File.expand_path('../boot', __FILE__)
$LOAD_PATH.push(File.join(File.dirname(__FILE__), "../lib")) ## 追加

require 'rails/all'
require 'utils/formatted_logger'　## 追加

module TestApp
  class Application < Rails::Application
    ## 追加する
    config.logger = Utils::FormattedLogger.create(config.paths['log'].first, 'weekly')
  end
end