Most UnknownHostExceptions thrown throughout hadoop include a useful message, either the hostname that was not found or some other descriptor of the problem. The UnknownHostException thrown from NetUtils.connect only includes the message of the underlying UnresolvedAddressException. If you take a look at the source for UnresolvedAddressException, it only has a no-args constructor (java11, but same is true in other versions). So it never has a message, meaning the UnknownHostException message is empty.
We should include the endpoint.toString() in the UnknownHostException thrown by NetUtils.connect
|Backport HADOOP-17837 to branch-3.2||Resolved||