     #     + `total`
     #     + `finished`
     #     + `total_pending_time`
-    #     + `total_processing_time`
+    #     + `total_process_time`
     #   3. Count processing tasks -- `LLEN` of `PROCESSING` list.
     #   4. Count failed task -- `LLEN` of `FAILED` list.
     #   5. Get identifiers of blocked group -- `SMEMBERS` of `BLOCKED` set.

      #
      # 1. Process `STATISTICS` hash:
      #   + Convert:
      #     - `total_pending_time` and `total_processing_time` into:
      #     - `average_pending_time` and `average_processing_time`
      #   + Calibrate initial condition (in case of no task is finished).
      # 2. Set `failed` key of returned object.
      statistics = multi_res[1] or {}

        process_time = finish_time - start_time
        multi.hincrby @key('STATISTICS'), 'finished', 1
        multi.hincrby @key('STATISTICS'), 'total_pending_time', start_time - task[task.length - 1]
        multi.hincrby @key('STATISTICS'), 'total_process_time', process_time
        multi.lpush @key('RECENT'), JSON.stringify([task..., finish_time])
        multi.ltrim @key('RECENT'), 0, @recent_size - 1
        multi.zadd @key('SLOWEST'), process_time, JSON.stringify([task..., start_time])
