Support a custom DnsAddressResolverGroup builder function (reactor#2745)

Support a user provided function to build a DnsAddressResolverGroup

docs/asciidoc/http-client.adoc

@@ -537,6 +537,7 @@ Default: 0.
 | `completeOncePreferredResolved` | When this setting is enabled, the resolver notifies as soon as all queries for the preferred address type are complete.
 When this setting is disabled, the resolver notifies when all possible address types are complete.
 This configuration is applicable for `DnsNameResolver#resolveAll(String)`. By default, this setting is enabled.
+| `dnsAddressResolverGroupProvider` | Sets a custom function to create a `DnsAddressResolverGroup` given a `DnsNameResolverBuilder`
 | `disableOptionalRecord` | Disables the automatic inclusion of an optional record that tries to give a hint to the remote DNS server about
 how much data the resolver can read per response. By default, this setting is enabled.
 | `disableRecursionDesired` | Specifies whether this resolver has to send a DNS query with the recursion desired (RD) flag set.

docs/asciidoc/tcp-client.adoc

@@ -419,6 +419,7 @@ The following listing shows the available configurations:
 | `completeOncePreferredResolved` | When this setting is enabled, the resolver notifies as soon as all queries for the preferred address type are complete.
 When this setting is disabled, the resolver notifies when all possible address types are complete.
 This configuration is applicable for `DnsNameResolver#resolveAll(String)`. By default, this setting is enabled.
+| `dnsAddressResolverGroupProvider` | Sets a custom function to create a `DnsAddressResolverGroup` given a `DnsNameResolverBuilder`
 | `disableOptionalRecord` | Disables the automatic inclusion of an optional record that tries to give a hint to the remote DNS server about
  how much data the resolver can read per response. By default, this setting is enabled.
 | `disableRecursionDesired` | Specifies whether this resolver has to send a DNS query with the recursion desired (RD) flag set.

reactor-netty-core/build.gradle

@@ -240,6 +240,8 @@ task japicmp(type: JapicmpTask) {
 	compatibilityChangeExcludes = [ "METHOD_NEW_DEFAULT" ]
 
 	methodExcludes = [
+			'reactor.netty.transport.NameResolverProvider#dnsAddressResolverGroupProvider()',
+			'reactor.netty.transport.NameResolverProvider$NameResolverSpec#dnsAddressResolverGroupProvider(java.util.function.Function)'
 	]
 }
 

reactor-netty-core/src/main/java/reactor/netty/transport/NameResolverProvider.java

@@ -38,6 +38,7 @@
 import java.time.Duration;
 import java.util.List;
 import java.util.Objects;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 /**
@@ -122,6 +123,16 @@ public interface NameResolverSpec {
 		 */
 		NameResolverSpec disableRecursionDesired(boolean disable);
 
+		/**
+		 * Sets the custom function to build the {@link DnsAddressResolverGroup} given a {@link DnsNameResolverBuilder}
+		 *
+		 * @param dnsAddressResolverGroupProvider the {@link DnsAddressResolverGroup} provider function
+		 * @return {@code this}
+		 * @since 1.1.6
+		 */
+		NameResolverSpec dnsAddressResolverGroupProvider(
+				Function<DnsNameResolverBuilder, DnsAddressResolverGroup> dnsAddressResolverGroupProvider);
+
 		/**
 		 * Specifies a custom {@link HostsFileEntriesResolver} to be used for hosts file entries.
 		 * Default to {@link DefaultHostsFileEntriesResolver}.
@@ -295,6 +306,17 @@ public Duration cacheNegativeTimeToLive() {
 		return cacheNegativeTimeToLive;
 	}
 
+	/**
+	 * Returns the configured custom provider of {@link DnsAddressResolverGroup} or null
+	 *
+	 * @return the configured custom provider of {@link DnsAddressResolverGroup} or null
+	 * @since 1.1.6
+	 */
+	@Nullable
+	public Function<DnsNameResolverBuilder, DnsAddressResolverGroup> dnsAddressResolverGroupProvider() {
+		return dnsAddressResolverGroupProvider;
+	}
+
 	/**
 	 * Returns the configured custom {@link HostsFileEntriesResolver} to be used for hosts file entries or null.
 	 *
@@ -452,6 +474,7 @@ public boolean equals(Object o) {
 		}
 		NameResolverProvider that = (NameResolverProvider) o;
 		return completeOncePreferredResolved == that.completeOncePreferredResolved &&
+				Objects.equals(dnsAddressResolverGroupProvider, that.dnsAddressResolverGroupProvider) &&
 				disableRecursionDesired == that.disableRecursionDesired &&
 				disableOptionalRecord == that.disableOptionalRecord &&
 				maxPayloadSize == that.maxPayloadSize &&
@@ -479,6 +502,7 @@ public int hashCode() {
 		result = 31 * result + Objects.hashCode(cacheMinTimeToLive);
 		result = 31 * result + Objects.hashCode(cacheNegativeTimeToLive);
 		result = 31 * result + Boolean.hashCode(completeOncePreferredResolved);
+		result = 31 * result + Objects.hashCode(dnsAddressResolverGroupProvider);
 		result = 31 * result + Boolean.hashCode(disableRecursionDesired);
 		result = 31 * result + Boolean.hashCode(disableOptionalRecord);
 		result = 31 * result + Objects.hashCode(loggingFactory);
@@ -547,6 +571,9 @@ public DnsAddressResolverGroup newNameResolverGroup(LoopResources defaultLoopRes
 		if (searchDomains != null) {
 			builder.searchDomains(searchDomains);
 		}
+		if (dnsAddressResolverGroupProvider != null) {
+			return dnsAddressResolverGroupProvider.apply(builder);
+		}
 		return roundRobinSelection ? new RoundRobinDnsAddressResolverGroup(builder) : new DnsAddressResolverGroup(builder);
 	}
 
@@ -570,11 +597,14 @@ public DnsAddressResolverGroup newNameResolverGroup(LoopResources defaultLoopRes
 	final boolean roundRobinSelection;
 	final Iterable<String> searchDomains;
 
+	final Function<DnsNameResolverBuilder, DnsAddressResolverGroup> dnsAddressResolverGroupProvider;
+
 	NameResolverProvider(Build build) {
 		this.cacheMaxTimeToLive = build.cacheMaxTimeToLive;
 		this.cacheMinTimeToLive = build.cacheMinTimeToLive;
 		this.cacheNegativeTimeToLive = build.cacheNegativeTimeToLive;
 		this.completeOncePreferredResolved = build.completeOncePreferredResolved;
+		this.dnsAddressResolverGroupProvider = build.dnsAddressResolverGroupProvider;
 		this.disableOptionalRecord = build.disableOptionalRecord;
 		this.disableRecursionDesired = build.disableRecursionDesired;
 		this.hostsFileEntriesResolver = build.hostsFileEntriesResolver;
@@ -622,6 +652,8 @@ static final class Build implements NameResolverSpec {
 		boolean roundRobinSelection;
 		Iterable<String> searchDomains;
 
+		Function<DnsNameResolverBuilder, DnsAddressResolverGroup> dnsAddressResolverGroupProvider;
+
 		@Override
 		public NameResolverSpec cacheMaxTimeToLive(Duration cacheMaxTimeToLive) {
 			this.cacheMaxTimeToLive = Objects.requireNonNull(cacheMaxTimeToLive);
@@ -658,6 +690,13 @@ public NameResolverSpec disableRecursionDesired(boolean disable) {
 			return this;
 		}
 
+		@Override
+		public NameResolverSpec dnsAddressResolverGroupProvider(
+				Function<DnsNameResolverBuilder, DnsAddressResolverGroup> dnsAddressResolverGroupProvider) {
+			this.dnsAddressResolverGroupProvider = Objects.requireNonNull(dnsAddressResolverGroupProvider);
+			return this;
+		}
+
 		@Override
 		public NameResolverSpec hostsFileEntriesResolver(HostsFileEntriesResolver hostsFileEntriesResolver) {
 			this.hostsFileEntriesResolver = Objects.requireNonNull(hostsFileEntriesResolver);

reactor-netty-core/src/test/java/reactor/netty/transport/NameResolverProviderTest.java

@@ -19,9 +19,12 @@
 import io.netty.handler.codec.dns.DnsRecord;
 import io.netty.handler.logging.LogLevel;
 import io.netty.resolver.ResolvedAddressTypes;
+import io.netty.resolver.dns.DnsAddressResolverGroup;
 import io.netty.resolver.dns.DnsCache;
 import io.netty.resolver.dns.DnsCacheEntry;
+import io.netty.resolver.dns.DnsNameResolverBuilder;
 import io.netty.resolver.dns.DnsServerAddressStreamProviders;
+import io.netty.resolver.dns.RoundRobinDnsAddressResolverGroup;
 import io.netty.resolver.dns.macos.MacOSDnsServerAddressStreamProvider;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -36,6 +39,7 @@
 import java.time.Duration;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -125,6 +129,15 @@ void completeOncePreferredResolved() {
 		assertThat(builder.build().isCompleteOncePreferredResolved()).isFalse();
 	}
 
+	@Test
+	void dnsAddressResolverGroupProvider() {
+		assertThat(builder.build().dnsAddressResolverGroupProvider()).isNull();
+
+		Function<DnsNameResolverBuilder, DnsAddressResolverGroup> provider = RoundRobinDnsAddressResolverGroup::new;
+		builder.dnsAddressResolverGroupProvider(provider);
+		assertThat(builder.build().dnsAddressResolverGroupProvider()).isEqualTo(provider);
+	}
+
 	@Test
 	void disableOptionalRecord() {
 		assertThat(builder.build().isDisableOptionalRecord()).isFalse();
@@ -143,10 +156,10 @@ void disableRecursionDesired() {
 
 	@Test
 	void hostsFileEntriesResolver() {
-		assertThat(builder.build().hostsFileEntriesResolver).isNull();
+		assertThat(builder.build().hostsFileEntriesResolver()).isNull();
 
 		builder.hostsFileEntriesResolver((inetHost, resolvedAddressTypes) -> null);
-		assertThat(builder.build().hostsFileEntriesResolver).isNotNull();
+		assertThat(builder.build().hostsFileEntriesResolver()).isNotNull();
 	}
 
 	@Test