Ruby/RackでログをLTSVで出す

今更感が強いですが実際ログをLTSVにすると扱いやすい場面に最近遭遇したので。

ltsv_formatter.rb

require 'logger'

class Logger
  class FreeFormatter < Formatter
    Format = "%{label}, [%{time}#%{pid}] %<severity>5s -- %{progname}: %{message}\n"

    attr_accessor :format

    def initialize(format=self.class::Format)
      @format = format || Format
      super()
    end

    def call(severity, time, progname, msg)
      @format % {
        :label => severity[0..0],
        :time => format_datetime(time),
        :pid => $$,
        :severity => severity,
        :progname => progname,
        :message => msg2str(msg)
      }
    end
  end

  class LTSVFormatter < FreeFormatter
    Format = %w[severity time progname pid message].map {|field|
      "#{field}:%{#{field}}"
    }.join("\t") + "\n"

    private

    def format_datetime(time)
      if @datetime_format.nil?
        time.strftime("%Y-%m-%dT%H:%M:%S.") << "%06d" % time.usec
      else
        super
      end
    end
  end
end

if __FILE__ == $0
  logger = Logger.new($stderr)
  logger.formatter = Logger::FreeFormatter.new
  logger.debug 'hello'
  logger.info 'world'
  logger.formatter = Logger::LTSVFormatter.new
  logger.warn 'hi'
  logger.error 'again'
end

ltsv_logger.ru

class LTSVLogger < Rack::CommonLogger
  FORMAT = %w[host user time method path query version status size].map {|field| "#{field}:%{#{field}}"}.join("\t") + "\truntime:%<runtime>0.4f\n"

  def log(env, status, header, began_at)
    now = Time.now
    length = extract_content_length(header)

    logger = @logger || env['rack.errors']
    logger.write FORMAT % {
      host:    env['HTTP_X_FORWARDED_FOR'] || env["REMOTE_ADDR"] || "-",
      user:    env["REMOTE_USER"] || "-",
      time:    now.strftime("%d/%b/%Y %H:%M:%S"),
      method:  env["REQUEST_METHOD"],
      path:    env["PATH_INFO"],
      query:   env["QUERY_STRING"].empty? ? "" : "?"+env["QUERY_STRING"],
      version: env["HTTP_VERSION"],
      status:  status.to_s[0..3],
      size:    length,
      runtime: now - began_at }
  end
end

use LTSVLogger
run lambda {|env|
  [200, {'Content-Type' => 'text/plain'}, ['Hello, LTSV']]
}