stackdriver_formatter.rb

require "logger"
require "json"
require "active_support"

# https://github.com/yfuruyama/stackdriver-request-context-log/blob/master/stackdriver.go
# severityの変換
# https://github.com/GoogleCloudPlatform/fluent-plugin-google-cloud/blob/master/lib/fluent/plugin/out_google_cloud.rb#L1737
module Rrp
  module Logger
    class StackdriverFormatter < ::Logger::Formatter
      include ActiveSupport::TaggedLogging::Formatter

      DEFAULT_PARAMS_PROC = proc { {} }

      attr_writer :params_proc

      def initialize(*_args)
        super
        @params_proc = nil
      end

      def call(severity, time, progname, msg)
        message_params = {}
        message_params[:severity] = severity
        message_params[:time] = time
        message_params[:progname] = progname
        message_params[:message] = msg2str(msg)
        message_params.merge!(build_params)

        # JSONで出力する
        message_params.to_json + "\n"
      end

      def self.global_formatter
        @global_formatter ||= self.new
      end

      private def build_params
        params_proc = @params_proc || DEFAULT_PARAMS_PROC
        params = params_proc.call
        raise ArgumentError, "request_info should be a Hash. it was #{params.inspect}" unless params.is_a? Hash

        params["logging.googleapis.com/trace"] = params[:request_id] if params[:request_id]
        params
      end

      private def msg2str(msg)
        case msg
        when ::String
          msg
        when ::Exception
          "#{msg.message} (#{msg.class}) #{msg.backtrace.inspect}"
        else
          msg.inspect
        end
      end
    end
  end
end