 
   # ### Re-Schedule Failed and Blocked Tasks
 
+  # Requeue the failed and blocked tasks into `SOURCE` list. Useful for failure
+  # recovery. **Usage:**
+  #
+  #     queue.reschedule () ->
+  #       console.log 'reschedule successed'
+  #
   #   1. Requeue tasks in the `FAILED` list into `SOURCE` list, and,
   #   2. Pop all blocked tasks (`QUEUED` lists listed in the `BLOCKED` set,
   #   without first task of each list, because that's the failed task


  # ### Poll New Task

  # If any task presents in the `SOURCE` list, `lpop` from `SOURCE`
  # (`rpush`) into `QUEUED`. The `lpop` and `rpush` are protected by a
  # transaction.
  #
  # Since the task being popped and pushed should be known in prior of the
  # begin of the transaction (aka, the `multi` command), we need to get the


  # ### Continue Process a Group

  # **Private** method. Upon successful execution of a task, or skipping a
  # failed task:
  #
  #   1. `lpop` the current task from `QUEUED` list.
