add ability to use RoundRobinDnsAddressResolverGroup in Connection manager.

redisson/src/main/java/org/redisson/config/Config.java

@@ -27,6 +27,7 @@ import org.redisson.codec.DefaultReferenceCodecProvider;
 import org.redisson.codec.JsonJacksonCodec;
 import org.redisson.codec.ReferenceCodecProvider;
 import org.redisson.connection.ConnectionManager;
+import org.redisson.connection.AddressResolverGroupFactory;
 import org.redisson.connection.ReplicatedConnectionManager;
 
 import io.netty.channel.EventLoopGroup;
@@ -86,6 +87,11 @@ public class Config {
     
     private boolean keepPubSubOrder = true;
     
+    /**
+     * AddressResolverGroupFactory switch between default and round robin
+     */
+    private AddressResolverGroupFactory addressResolverGroupFactory = AddressResolverGroupFactory.DNS_ADDRESS_RESOLVER_GROUP;
+
     public Config() {
     }
 
@@ -107,7 +113,8 @@ public class Config {
         setReferenceEnabled(oldConf.isReferenceEnabled());
         setEventLoopGroup(oldConf.getEventLoopGroup());
         setTransportMode(oldConf.getTransportMode());
-        
+        setAddressResolverGroupFactory(oldConf.getAddressResolverGroupFactory());
+
         if (oldConf.getSingleServerConfig() != null) {
             setSingleServerConfig(new SingleServerConfig(oldConf.getSingleServerConfig()));
         }
@@ -591,6 +598,13 @@ public class Config {
         return keepPubSubOrder;
     }
 
+    public void setAddressResolverGroupFactory(AddressResolverGroupFactory addressResolverGroupFactory) {
+        this.addressResolverGroupFactory = addressResolverGroupFactory;
+    }
+
+    public AddressResolverGroupFactory getAddressResolverGroupFactory() {
+        return addressResolverGroupFactory;
+    }
 
     /**
      * Read config object stored in JSON format from <code>String</code>

redisson/src/main/java/org/redisson/connection/AddressResolverGroupFactory.java

@@ -0,0 +1,16 @@
+package org.redisson.connection;
+
+import io.netty.channel.socket.DatagramChannel;
+import io.netty.resolver.dns.DnsAddressResolverGroup;
+import io.netty.resolver.dns.DnsServerAddressStreamProvider;
+import io.netty.resolver.dns.RoundRobinDnsAddressResolverGroup;
+
+/**
+ * Created by hasaadon on 15/02/2018.
+ */
+public interface AddressResolverGroupFactory {
+    DnsAddressResolverGroup create(Class<? extends DatagramChannel> channelType, DnsServerAddressStreamProvider nameServerProvider);
+
+    AddressResolverGroupFactory ROUND_ROBIN_DNS_ADDRESS_RESOLVER_GROUP = RoundRobinDnsAddressResolverGroup::new;
+    AddressResolverGroupFactory DNS_ADDRESS_RESOLVER_GROUP = DnsAddressResolverGroup::new;
+}

redisson/src/main/java/org/redisson/connection/MasterSlaveConnectionManager.java

@@ -190,7 +190,7 @@ public class MasterSlaveConnectionManager implements ConnectionManager {
             }
 
             this.socketChannelClass = EpollSocketChannel.class;
-            this.resolverGroup = new DnsAddressResolverGroup(EpollDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
+            this.resolverGroup = cfg.getAddressResolverGroupFactory().create(EpollDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
         } else if (cfg.getTransportMode() == TransportMode.KQUEUE) {
             if (cfg.getEventLoopGroup() == null) {
                 this.group = new KQueueEventLoopGroup(cfg.getNettyThreads(), new DefaultThreadFactory("redisson-netty"));
@@ -199,7 +199,7 @@ public class MasterSlaveConnectionManager implements ConnectionManager {
             }
 
             this.socketChannelClass = KQueueSocketChannel.class;
-            this.resolverGroup = new DnsAddressResolverGroup(KQueueDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
+            this.resolverGroup = cfg.getAddressResolverGroupFactory().create(KQueueDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
         } else {
             if (cfg.getEventLoopGroup() == null) {
                 this.group = new NioEventLoopGroup(cfg.getNettyThreads(), new DefaultThreadFactory("redisson-netty"));
@@ -208,7 +208,7 @@ public class MasterSlaveConnectionManager implements ConnectionManager {
             }
 
             this.socketChannelClass = NioSocketChannel.class;
-            this.resolverGroup = new DnsAddressResolverGroup(NioDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
+            this.resolverGroup = cfg.getAddressResolverGroupFactory().create(NioDatagramChannel.class, DnsServerAddressStreamProviders.platformDefault());
         }
         
         if (cfg.getExecutor() == null) {