HDFS-9427 (HDFS should not default to ephemeral ports), we changed all default ports to ephemeral ports, which is very appreciated by admin. As part of that change, we also modified the NN RPC port from the famous 8020 to 9820, to be closer to other ports changed there.
With more integration going on, it appears that all the other ephemeral port changes are fine, but the NN RPC port change is painful for downstream on migrating to Hadoop 3. Some examples include:
- Hive table locations pointing to hdfs://nn:port/dir
- Downstream minicluster unit tests that assumed 8020
- Oozie workflows / downstream scripts that used 8020
This isn't a problem for HA URLs, since that does not include the port number. But considering the downstream impact, instead of requiring all of them change their stuff, it would be a way better experience to leave the NN port unchanged. This will benefit Hadoop 3 adoption and ease unnecessary upgrade burdens.
It is of course incompatible, but giving 3.0.0 is just out, IMO it worths to switch the port back.