Deprecate DnsResolver in favor of AddressResolverGroup(#1572) (#3291)

* Deprecate DnsResolver in favor of AddressResolverGroup(#1572)

* Mark DnsResolver and related API as @deprecated

* DefaultClientResources now unconditionally uses DnsAddressResolverGroup

* Update test coverage to reflect new default behavior

* Polishing

---------

Co-authored-by: Tihomir Mateev <tihomir.mateev@gmail.com>

Author: young0264

pom.xml

@@ -256,7 +256,6 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-resolver-dns</artifactId>
-            <optional>true</optional>
         </dependency>
 
         <dependency>

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

@@ -1,44 +1,29 @@
 package io.lettuce.core.resource;
 
-import io.lettuce.core.internal.LettuceClassUtils;
 import io.netty.channel.socket.SocketChannel;
 import io.netty.resolver.AddressResolverGroup;
 import io.netty.resolver.DefaultAddressResolverGroup;
 import io.netty.resolver.dns.DefaultDnsCache;
 import io.netty.resolver.dns.DefaultDnsCnameCache;
 import io.netty.resolver.dns.DnsAddressResolverGroup;
 import io.netty.resolver.dns.DnsNameResolverBuilder;
-import io.netty.util.internal.logging.InternalLogger;
-import io.netty.util.internal.logging.InternalLoggerFactory;
 
 /**
  * Wraps and provides {@link AddressResolverGroup} classes. This is to protect the user from {@link ClassNotFoundException}'s
  * caused by the absence of the {@literal netty-dns-resolver} library during runtime. This class will be deleted when
  * {@literal netty-dns-resolver} becomes mandatory. Internal API.
+ * <p>
+ * Since Lettuce 6.7, {@literal netty-dns-resolver} became a required dependency so this class now unconditionally uses
+ * {@link DnsAddressResolverGroup}
  *
  * @author Yohei Ueki
  * @author Mark Paluch
+ * @author Euiyoung Nam
  * @since 6.1
  */
 class AddressResolverGroupProvider {
 
-    private static final InternalLogger logger = InternalLoggerFactory.getInstance(AddressResolverGroupProvider.class);
-
-    private static final AddressResolverGroup<?> ADDRESS_RESOLVER_GROUP;
-
-    static {
-        boolean dnsResolverAvailable = LettuceClassUtils.isPresent("io.netty.resolver.dns.DnsAddressResolverGroup");
-
-        AddressResolverGroup<?> group;
-        if (dnsResolverAvailable) {
-            logger.debug("Starting with netty's non-blocking DNS resolver library");
-            group = DefaultDnsAddressResolverGroupWrapper.INSTANCE;
-        } else {
-            logger.debug("Starting without optional netty's non-blocking DNS resolver library");
-            group = DefaultAddressResolverGroup.INSTANCE;
-        }
-        ADDRESS_RESOLVER_GROUP = group;
-    }
+    private static final AddressResolverGroup<?> ADDRESS_RESOLVER_GROUP = DefaultDnsAddressResolverGroupWrapper.INSTANCE;
 
     /**
      * Returns the {@link AddressResolverGroup} for DNS resolution.

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

@@ -56,6 +56,7 @@
  * @author Mark Paluch
  * @author Mikhael Sokolov
  * @author Yohei Ueki
+ * @author Euiyoung Nam
  * @since 3.4
  * @see DefaultClientResources
  */
@@ -361,7 +362,9 @@ default Builder commandLatencyCollector(CommandLatencyCollector commandLatencyCo
      *
      * @return the DNS resolver.
      * @since 4.3
+     * @deprecated since 6.6 replaced by{@link AddressResolverGroup} instead.
      */
+    @Deprecated
     DnsResolver dnsResolver();
 
     /**

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

@@ -79,6 +79,7 @@
  *
  * @author Mark Paluch
  * @author Yohei Ueki
+ * @author Euiyoung Nam
  * @since 3.4
  */
 public class DefaultClientResources implements ClientResources {
@@ -786,6 +787,10 @@ public int computationThreadPoolSize() {
         return LettuceLists.newList(eventExecutorGroup.iterator()).size();
     }
 
+    /**
+     * @deprecated since 6.7 replaced by{@link AddressResolverGroup} instead.
+     **/
+    @Deprecated
     @Override
     public DnsResolver dnsResolver() {
         return dnsResolver;

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

@@ -2,18 +2,21 @@
 
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import io.netty.resolver.AddressResolverGroup;
 
 /**
  * Users may implement this interface to override the normal DNS lookup offered by the OS.
  *
  * @author Mark Paluch
+ * @author Euiyoung Nam
  * @since 4.2
  */
 public interface DnsResolver {
 
     /**
      * Java VM default resolver.
      *
+     * @deprecated since 6.7, see {@link AddressResolverGroup}
      * @since 5.1
      */
     static DnsResolver jvmDefault() {

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

@@ -1,5 +1,7 @@
 package io.lettuce.core.resource;
 
+import io.netty.resolver.AddressResolverGroup;
+
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 
@@ -13,6 +15,8 @@ public enum DnsResolvers implements DnsResolver {
 
     /**
      * Java VM default resolver.
+     *
+     * @deprecated since 6.7. Configure {@link AddressResolverGroup} instead.
      */
     JVM_DEFAULT {
 

src/test/java/io/lettuce/core/resource/DefaultClientResourcesUnitTests.java

@@ -27,6 +27,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 
+import io.netty.resolver.dns.DnsAddressResolverGroup;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
 
@@ -112,6 +113,15 @@ void testDnsResolver() {
         assertThat(sut.dnsResolver()).isEqualTo(dirContextDnsResolver);
     }
 
+    @Test
+    void testShouldUseDnsAddressResolverGroup() {
+        DefaultClientResources sut = DefaultClientResources.create();
+        AddressResolverGroup<?> addressResolverGroup = sut.addressResolverGroup();
+
+        assertThat(addressResolverGroup).as("Default AddressResolverGroup should be DnsAddressResolverGroup")
+                .isInstanceOf(DnsAddressResolverGroup.class);
+    }
+
     @Test
     void testProvidedResources() {