Resolve hostname of node again during reconnection

This is essential when memcached cluster is built on cloud infra, e.g.
k8s, where nodes move and their ips vary.

src/main/java/net/spy/memcached/MemcachedConnection.java

@@ -1131,7 +1131,7 @@ private void attemptReconnects() {
           ch.configureBlocking(false);
           ch.socket().setTcpNoDelay(!connectionFactory.useNagleAlgorithm());
           int ops = 0;
-          if (ch.connect(node.getSocketAddress())) {
+          if (ch.connect(node.getSocketAddress(true))) {
             connected(node);
             addedQueue.offer(node);
             getLogger().info("Immediately reconnected to %s", node);

src/main/java/net/spy/memcached/MemcachedNode.java

@@ -135,6 +135,14 @@ public interface MemcachedNode {
    */
   SocketAddress getSocketAddress();
 
+  /**
+   * Get the SocketAddress of the server to which this node is connected, and resolve it again if specified.
+   *
+   * @param resolve whether to resolve and update the address
+   * @return The SocketAddress of the server to which this node is connected
+   */
+  SocketAddress getSocketAddress(boolean resolve);
+
   /**
    * True if this node is <q>active.</q> i.e. is is currently connected and
    * expected to be able to process requests

src/main/java/net/spy/memcached/MemcachedNodeROImpl.java

@@ -106,6 +106,10 @@ public SocketAddress getSocketAddress() {
     return root.getSocketAddress();
   }
 
+  public SocketAddress getSocketAddress(boolean resolve) {
+    return root.getSocketAddress(resolve);
+  }
+
   public ByteBuffer getWbuf() {
     throw new UnsupportedOperationException();
   }

src/main/java/net/spy/memcached/protocol/TCPMemcachedNodeImpl.java

@@ -24,6 +24,7 @@
 package net.spy.memcached.protocol;
 
 import java.io.IOException;
+import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.nio.ByteBuffer;
 import java.nio.channels.SelectionKey;
@@ -51,7 +52,7 @@
 public abstract class TCPMemcachedNodeImpl extends SpyObject implements
     MemcachedNode {
 
-  private final SocketAddress socketAddress;
+  private SocketAddress socketAddress;
   private final ByteBuffer rbuf;
   private final ByteBuffer wbuf;
   protected final BlockingQueue<Operation> writeQ;
@@ -426,6 +427,22 @@ public final ByteBuffer getWbuf() {
    * @see net.spy.memcached.MemcachedNode#getSocketAddress()
    */
   public final SocketAddress getSocketAddress() {
+    return getSocketAddress(false);
+  }
+
+  public final SocketAddress getSocketAddress(boolean resolve) {
+    if (resolve && socketAddress instanceof InetSocketAddress) {
+      InetSocketAddress originalAddress = (InetSocketAddress) socketAddress;
+      InetSocketAddress resolvedAddress = new InetSocketAddress(
+          originalAddress.getHostName(), originalAddress.getPort());
+
+      if (!originalAddress.equals(resolvedAddress)) {
+        socketAddress = resolvedAddress;
+        getLogger().info("node address changed from %s to %s",
+            originalAddress, resolvedAddress);
+      }
+    }
+
     return socketAddress;
   }
 

src/test/java/net/spy/memcached/MockMemcachedNode.java

@@ -43,6 +43,10 @@ public SocketAddress getSocketAddress() {
     return socketAddress;
   }
 
+  public SocketAddress getSocketAddress(boolean resolve) {
+    return socketAddress; // sufficiently good
+  }
+
   public MockMemcachedNode(InetSocketAddress socketAddress) {
     this.socketAddress = socketAddress;
   }

src/test/java/net/spy/memcached/protocol/binary/AddressResolutionTest.java

@@ -0,0 +1,54 @@
+package net.spy.memcached.protocol.binary;
+
+import junit.framework.Assert;
+import net.spy.memcached.DefaultConnectionFactory;
+import net.spy.memcached.MemcachedNode;
+import net.spy.memcached.ops.Operation;
+import org.junit.Test;
+
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.channels.SocketChannel;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+
+public class AddressResolutionTest {
+  @Test
+  public void testResolveAddressWithHostname() throws Exception {
+    BlockingQueue<Operation> queue = new ArrayBlockingQueue<>(1);
+    MemcachedNode node = new BinaryMemcachedNodeImpl(new InetSocketAddress("memcached.org", 80),
+        SocketChannel.open(), 1024, queue, queue, queue, 1024L, false,
+        1024, 1024, new DefaultConnectionFactory());
+      SocketAddress originalSocketAddress = node.getSocketAddress();
+      SocketAddress resolvedSocketAddress = node.getSocketAddress(true);
+      Assert.assertEquals("socket address with hostname couldn't be resolved",
+          originalSocketAddress, resolvedSocketAddress);
+  }
+
+  @Test
+  public void testResolveAddressWithAddress() throws Exception {
+    BlockingQueue<Operation> queue = new ArrayBlockingQueue<>(1);
+    MemcachedNode node = new BinaryMemcachedNodeImpl(
+        new InetSocketAddress(InetAddress.getByName("memcached.org"), 80),
+        SocketChannel.open(), 1024, queue, queue, queue, 1024L, false,
+        1024, 1024, new DefaultConnectionFactory());
+    SocketAddress originalSocketAddress = node.getSocketAddress();
+    SocketAddress resolvedSocketAddress = node.getSocketAddress(true);
+    Assert.assertEquals("socket address with address couldn't be resolved",
+        originalSocketAddress, resolvedSocketAddress);
+  }
+
+  @Test
+  public void testResolveAddressWithAddressAsHostname() throws Exception {
+    BlockingQueue<Operation> queue = new ArrayBlockingQueue<>(1);
+    MemcachedNode node = new BinaryMemcachedNodeImpl(
+        new InetSocketAddress(InetAddress.getByName("memcached.org").getHostAddress(), 80),
+        SocketChannel.open(), 1024, queue, queue, queue, 1024L, false,
+        1024, 1024, new DefaultConnectionFactory());
+    SocketAddress originalSocketAddress = node.getSocketAddress();
+    SocketAddress resolvedSocketAddress = node.getSocketAddress(true);
+    Assert.assertEquals("socket address with address as hostname couldn't be resolved",
+        originalSocketAddress, resolvedSocketAddress);
+  }
+}