HDFS-13639 improves the performance of short-circuit shm slot releasing by reusing the domain socket that the client previously used to send release request to the DataNode.
This is good when there are only one DataNode locates with the client (truth in most of the production environment). However, if we launch multiple DataNodes on a machine (usually for testing, e.g. Impala's end-to-end tests), the request could be sent to the wrong DataNode. See an example in