/**
  * 获取一个任务
  *
  * @return bool|Caster
  */
 private function getReadyJob()
 {
     $keyChip = $this->queue->name . ':' . Job::JOBS_TAB . ':' . $this->tube . ':';
     $timePort = Util::now();
     $this->expireActivate($keyChip, $timePort);
     if (!($id = $this->pop($keyChip . Job::STATE_READY, $timePort))) {
         return false;
     }
     if (!($job = Caster::reload($id))) {
         return false;
     }
     $this->client->hIncrBy($this->queue->name . ':' . Job::JOB_TAB . ':' . $id, 'retry_times', 1);
     $this->jobId = $id;
     $this->periodic = $this->client->hGet($this->queue->name . ':' . Job::JOB_TAB . ':' . $id, 'periodic');
     return $job;
 }