Add jitter on the processor fetch backoff sleep (#868)

processor.go

@@ -181,7 +181,8 @@ func (p *processor) exec() {
  // Sleep to avoid slamming redis and let scheduler move tasks into queues.
  // Note: We are not using blocking pop operation and polling queues instead.
  // This adds significant load to redis.
- time.Sleep(p.taskCheckInterval)
+ jitter := time.Duration(rand.Intn(int(p.taskCheckInterval)))
+ time.Sleep(p.taskCheckInterval/2 + jitter)
  <-p.sema // release token
  return
  case err != nil: