基于Redis 的任务队列Bull -- （十五）failed

bull 中 job 的 moveToFailed 和 moveToCompleted 虽然非常像，都调用了 moveToFinished 方法

但实际上 moveToFailed 还有其它的复杂处理逻辑

首先会保存错误和调用堆栈

Job.prototype.moveToFailed = async function(err, ignoreLock) {
  err = err || { message: 'Unknown reason' };

  this.failedReason = err.message;

  await this.queue.isReady();

  let command;
  const multi = this.queue.client.multi();
  this._saveAttempt(multi, err);

_saveAttempt 将 attemptsMade++, stacktrace 和 failedReason 保存到 job 数据的 hash 中

Job.prototype._saveAttempt = function(multi, err) {
  this.attemptsMade++;

  const params = {
    attemptsMade: this.attemptsMade
  };

  if (this.opts