何度も手でdigdag logを打つのは面倒
digdag logは時々「error: Attempted read on closed stream. (io)」エラーになる(0.9.4にて)
digdag UIはログの取りこぼしがある(0.9.4にて)

digdag_log.rb

require 'open3'

STDOUT.sync = true

attempt_id = ARGV[0]

log_line_no_max = 0
attempt_stdout = nil

loop do
  # digdag attempt実行 (エラーなら即終了)
  status = nil
  attempt_stdout = []
  Open3.popen3("digdag attempt " + attempt_id) do |stdin, stdout, stderr, wait_thr|
    stdout.each do |line|
      tmp = line.match(/  status: (.+)/)
      status = tmp[1] unless tmp.nil?
      attempt_stdout << line
    end
    unless wait_thr.value.success?
      stdout.each do |line|        puts line end
      stderr.each do |line| STDERR.puts line end
      abort
    end
  end

  # digdag log実行 (正常終了するまで繰り返す)
  loop do
    log_line_no = 0
    log_success = false
    Open3.popen3("digdag log " + attempt_id) do |stdin, stdout, stderr, wait_thr|
      stdout.each do |line|
        log_line_no += 1
        # 前回出力行以降を出力
        if (log_line_no > log_line_no_max)
          puts line
          log_line_no_max = log_line_no
        end
      end
      log_success = wait_thr.value.success?
    end
    if log_success
      break
    end
  end

  # attemptが終了しているか
  if status == "error" || status == "success"
    break
  end

  # 次の実行までスリープ
  sleep 10
end

puts
puts "this attempt ended with following status"
puts
puts attempt_stdout

ruby digdag_log.rb 6