Accept cluster nodes without hostname.

RedisNode can now be constructed using an empty hostname. This can happen when a node is in failover state. RedisNode exposes hasValidHost() to check whether the node has a valid hostname.

Also, introduce copy constructor to avoid mutations caused by the builder.

Closes #1985
Original Pull Request: #1991

src/main/java/org/springframework/data/redis/connection/ClusterTopology.java

@@ -197,11 +197,11 @@ public class ClusterTopology {
 
 		Assert.notNull(node, "RedisClusterNode must not be null!");
 
-		if (nodes.contains(node) && StringUtils.hasText(node.getHost()) && StringUtils.hasText(node.getId())) {
+		if (nodes.contains(node) && node.hasValidHost() && StringUtils.hasText(node.getId())) {
 			return node;
 		}
 
-		if (StringUtils.hasText(node.getHost()) && node.getPort() != null) {
+		if (node.hasValidHost() && node.getPort() != null) {
 			return lookup(node.getHost(), node.getPort());
 		}
 

src/main/java/org/springframework/data/redis/connection/RedisNode.java

@@ -18,6 +18,7 @@ package org.springframework.data.redis.connection;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * @author Christoph Strobl
@@ -50,6 +51,16 @@ public class RedisNode implements NamedNode {
 
 	protected RedisNode() {}
 
+	private RedisNode(RedisNode redisNode) {
+
+		this.id = redisNode.id;
+		this.name = redisNode.name;
+		this.host = redisNode.host;
+		this.port = redisNode.port;
+		this.type = redisNode.type;
+		this.masterId = redisNode.masterId;
+	}
+
 	/**
 	 * @return can be {@literal null}.
 	 */
@@ -58,6 +69,14 @@ public class RedisNode implements NamedNode {
 		return host;
 	}
 
+	/**
+	 * @return whether this node has a valid host (not null and not empty).
+	 * @since 2.3.8
+	 */
+	public boolean hasValidHost() {
+		return StringUtils.hasText(host);
+	}
+
 	/**
 	 * @return can be {@literal null}.
 	 */
@@ -229,7 +248,7 @@ public class RedisNode implements NamedNode {
 		 */
 		public RedisNodeBuilder listeningAt(String host, int port) {
 
-			Assert.hasText(host, "Hostname must not be empty or null.");
+			Assert.notNull(host, "Hostname must not be null.");
 			node.host = host;
 			node.port = port;
 			return this;
@@ -290,7 +309,7 @@ public class RedisNode implements NamedNode {
 		 * @return
 		 */
 		public RedisNode build() {
-			return this.node;
+			return new RedisNode(this.node);
 		}
 	}
 

src/main/java/org/springframework/data/redis/connection/convert/Converters.java

@@ -554,6 +554,7 @@ abstract public class Converters {
 		static final int LINK_STATE_INDEX = 7;
 		static final int SLOTS_INDEX = 8;
 
+		@Override
 		public RedisClusterNode convert(String source) {
 
 			String[] args = source.split(" ");

src/main/java/org/springframework/data/redis/connection/jedis/JedisClusterConnection.java

@@ -951,6 +951,11 @@ public class JedisClusterConnection implements DefaultedRedisClusterConnection {
 
 			RedisClusterNode member = topologyProvider.getTopology().lookup(node);
 
+			if (!member.hasValidHost()) {
+				throw new DataAccessResourceFailureException(String
+						.format("Cannot obtain connection to node %ss as it is not associated with a hostname!", node.getId()));
+			}
+
 			if (member != null && connectionHandler != null) {
 				return connectionHandler.getConnectionFromNode(new HostAndPort(member.getHost(), member.getPort()));
 			}