Major Description
While reviewing HDFS-11493, cheersyang commented that it would be a good idea to support priority for datanode commands send from SCM.
The queue seems to be time ordered, I think it will be better to support priority as well. Commands may have different priority, for example, replicate a container priority is usually higher than delete a container replica; replicate a container also may have different priorities according to the number of replicas
This jira tracks that work item.