Resolve hostnames using netty's non-blocking DNS resolver #1498

We now use netty's non-blocking DNS resolver upon connect.

pom.xml

@@ -154,6 +154,11 @@
             <artifactId>netty-handler</artifactId>
         </dependency>
 
+        <dependency>
+            <groupId>io.netty</groupId>
+            <artifactId>netty-resolver-dns</artifactId>
+        </dependency>
+
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-transport</artifactId>

src/main/java/io/lettuce/core/AbstractRedisClient.java

@@ -54,6 +54,9 @@
 import io.netty.channel.group.ChannelGroup;
 import io.netty.channel.group.DefaultChannelGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.resolver.dns.DnsAddressResolverGroup;
+import io.netty.resolver.dns.DnsNameResolverBuilder;
 import io.netty.util.concurrent.EventExecutorGroup;
 import io.netty.util.concurrent.Future;
 import io.netty.util.internal.logging.InternalLogger;
@@ -73,6 +76,7 @@
  * @author Mark Paluch
  * @author Jongyeol Choi
  * @author Poorva Gokhale
+ * @author Yohei Ueki
  * @since 3.0
  * @see ClientResources
  */
@@ -297,6 +301,17 @@ protected void channelType(ConnectionBuilder connectionBuilder, ConnectionPoint
         }
     }
 
+    protected void resolver(ConnectionBuilder connectionBuilder, ConnectionPoint connectionPoint) {
+
+        LettuceAssert.notNull(connectionPoint, "ConnectionPoint must not be null");
+
+        if (connectionPoint.getSocket() == null) {
+            connectionBuilder.bootstrap().resolver(
+                    new DnsAddressResolverGroup(new DnsNameResolverBuilder().channelType(Transports.datagramChannelClass())
+                            .socketChannelType(Transports.socketChannelClass().asSubclass(SocketChannel.class))));
+        }
+    }
+
     private EventLoopGroup getEventLoopGroup(ConnectionPoint connectionPoint) {
 
         for (;;) {

src/main/java/io/lettuce/core/RedisClient.java

@@ -75,6 +75,7 @@
  *
  * @author Will Glozer
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @see RedisURI
  * @see StatefulRedisConnection
  * @see RedisFuture
@@ -322,6 +323,7 @@ private <K, V, S> ConnectionFuture<S> connectStatefulAsync(StatefulRedisConnecti
         connectionBuilder(getSocketAddressSupplier(redisURI), connectionBuilder, redisURI);
         connectionBuilder.connectionInitializer(createHandshake(state));
         channelType(connectionBuilder, redisURI);
+        resolver(connectionBuilder, redisURI);
 
         ConnectionFuture<RedisChannelHandler<K, V>> future = initializeChannelAsync(connectionBuilder);
 
@@ -599,6 +601,7 @@ private <K, V> ConnectionFuture<StatefulRedisSentinelConnection<K, V>> doConnect
         connectionBuilder(getSocketAddressSupplier(redisURI), connectionBuilder, redisURI);
 
         channelType(connectionBuilder, redisURI);
+        resolver(connectionBuilder, redisURI);
         ConnectionFuture<?> sync = initializeChannelAsync(connectionBuilder);
 
         return sync.thenApply(ignore -> (StatefulRedisSentinelConnection<K, V>) connection).whenComplete((ignore, e) -> {

src/main/java/io/lettuce/core/Transports.java

@@ -22,13 +22,16 @@
 import io.netty.channel.Channel;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.DatagramChannel;
+import io.netty.channel.socket.nio.NioDatagramChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
 
 /**
  * Transport infrastructure utility class. This class provides {@link EventLoopGroup} and {@link Channel} classes for socket and
  * native socket transports.
  *
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @since 4.4
  */
 class Transports {
@@ -57,6 +60,18 @@ static Class<? extends Channel> socketChannelClass() {
         return NioSocketChannel.class;
     }
 
+    /**
+     * @return the default {@link DatagramChannel} for socket (network/UDP) transport.
+     */
+    static Class<? extends DatagramChannel> datagramChannelClass() {
+
+        if (NativeTransports.isSocketSupported()) {
+            return NativeTransports.datagramChannelClass();
+        }
+
+        return NioDatagramChannel.class;
+    }
+
     /**
      * Native transport support.
      */
@@ -79,6 +94,13 @@ static Class<? extends Channel> socketChannelClass() {
             return RESOURCES.socketChannelClass();
         }
 
+        /**
+         * @return the native transport socket {@link DatagramChannel} class.
+         */
+        static Class<? extends DatagramChannel> datagramChannelClass() {
+            return RESOURCES.datagramChannelClass();
+        }
+
         /**
          * @return the native transport domain socket {@link Channel} class.
          */

src/main/java/io/lettuce/core/cluster/RedisClusterClient.java

@@ -135,6 +135,7 @@
  * possible.
  *
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @since 3.0
  * @see RedisURI
  * @see StatefulRedisClusterConnection
@@ -815,6 +816,7 @@ private <K, V> ConnectionBuilder createConnectionBuilder(RedisChannelHandler<K,
         connectionBuilder.commandHandler(commandHandlerSupplier);
         connectionBuilder(socketAddressSupplier, connectionBuilder, connectionSettings);
         channelType(connectionBuilder, connectionSettings);
+        resolver(connectionBuilder, connectionSettings);
 
         return connectionBuilder;
     }

src/main/java/io/lettuce/core/resource/EpollProvider.java

@@ -22,9 +22,11 @@
 import io.netty.channel.Channel;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.epoll.Epoll;
+import io.netty.channel.epoll.EpollDatagramChannel;
 import io.netty.channel.epoll.EpollDomainSocketChannel;
 import io.netty.channel.epoll.EpollEventLoopGroup;
 import io.netty.channel.epoll.EpollSocketChannel;
+import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.unix.DomainSocketAddress;
 import io.netty.util.concurrent.EventExecutorGroup;
 import io.netty.util.internal.SystemPropertyUtil;
@@ -36,6 +38,7 @@
  * the {@literal netty-transport-native-epoll} library during runtime. Internal API.
  *
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @since 4.4
  */
 public class EpollProvider {
@@ -153,6 +156,13 @@ public Class<? extends Channel> socketChannelClass() {
             return null;
         }
 
+        @Override
+        public Class<? extends DatagramChannel> datagramChannelClass() {
+
+            checkForEpollLibrary();
+            return null;
+        }
+
     }
 
     /**
@@ -194,6 +204,14 @@ public Class<? extends Channel> socketChannelClass() {
             return EpollSocketChannel.class;
         }
 
+        @Override
+        public Class<? extends DatagramChannel> datagramChannelClass() {
+
+            checkForEpollLibrary();
+
+            return EpollDatagramChannel.class;
+        }
+
         @Override
         public Class<? extends EventLoopGroup> eventLoopGroupClass() {
 

src/main/java/io/lettuce/core/resource/EventLoopResources.java

@@ -21,12 +21,14 @@
 import io.netty.channel.Channel;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.epoll.EpollEventLoopGroup;
+import io.netty.channel.socket.DatagramChannel;
 import io.netty.util.concurrent.EventExecutorGroup;
 
 /**
  * Interface to encapsulate EventLoopGroup resources.
  *
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @since 6.0
  */
 public interface EventLoopResources {
@@ -58,6 +60,11 @@ public interface EventLoopResources {
      */
     Class<? extends Channel> socketChannelClass();
 
+    /**
+     * @return the {@link DatagramChannel} class.
+     */
+    Class<? extends DatagramChannel> datagramChannelClass();
+
     /**
      * @return the {@link EventLoopGroup} class.
      */

src/main/java/io/lettuce/core/resource/KqueueProvider.java

@@ -22,9 +22,11 @@
 import io.netty.channel.Channel;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.kqueue.KQueue;
+import io.netty.channel.kqueue.KQueueDatagramChannel;
 import io.netty.channel.kqueue.KQueueDomainSocketChannel;
 import io.netty.channel.kqueue.KQueueEventLoopGroup;
 import io.netty.channel.kqueue.KQueueSocketChannel;
+import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.unix.DomainSocketAddress;
 import io.netty.util.concurrent.EventExecutorGroup;
 import io.netty.util.internal.SystemPropertyUtil;
@@ -36,6 +38,7 @@
  * the {@literal netty-transport-native-kqueue} library during runtime. Internal API.
  *
  * @author Mark Paluch
+ * @author Yohei Ueki
  * @since 4.4
  */
 public class KqueueProvider {
@@ -153,6 +156,15 @@ public Class<? extends Channel> socketChannelClass() {
             return null;
         }
 
+        @Override
+        public Class<? extends DatagramChannel> datagramChannelClass() {
+
+
+            checkForKqueueLibrary();
+            return null;
+        }
+
+
     }
 
     /**
@@ -194,6 +206,15 @@ public Class<? extends Channel> socketChannelClass() {
             return KQueueSocketChannel.class;
         }
 
+        @Override
+        public Class<? extends DatagramChannel> datagramChannelClass() {
+
+            checkForKqueueLibrary();
+
+            return KQueueDatagramChannel.class;
+        }
+
+
         @Override
         public Class<? extends EventLoopGroup> eventLoopGroupClass() {