HDFS-15250. Setting `dfs.client.use.datanode.hostname` to true can crash the system because of unhandled UnresolvedAddressException. Contributed by Ctest.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/client/impl/BlockReaderFactory.java

@@ -27,6 +27,7 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.lang.reflect.Constructor;
 import java.net.InetSocketAddress;
+import java.nio.channels.UnresolvedAddressException;
 import java.util.List;
 
 import com.google.common.io.ByteArrayDataOutput;
@@ -823,7 +824,7 @@ public class BlockReaderFactory implements ShortCircuitReplicaCreator {
           datanode);
       LOG.trace("nextTcpPeer: created newConnectedPeer {}", peer);
       return new BlockReaderPeer(peer, false);
-    } catch (IOException e) {
+    } catch (IOException | UnresolvedAddressException e) {
       LOG.trace("nextTcpPeer: failed to create newConnectedPeer connected to"
           + "{}", datanode);
       throw e;