Use InetAddressResolverProvider and add tests

driver-core/src/main/com/mongodb/MongoClientSettings.java

@@ -184,12 +184,10 @@ public DnsClient getDnsClient() {
     }
 
     /**
-     * Gets the {@link InetAddressResolver} to use for looking up the {@link java.net.InetAddress} instances for each host.
-     *
-     * <p>If set, it will be used to look up the {@link java.net.InetAddress} for each host, via
-     * {@link InetAddressResolver#lookupByName(String)}. Otherwise, {@link java.net.InetAddress#getAllByName(String)} will be used.
+     * Gets the explicitly set {@link InetAddressResolver} to use for looking up the {@link java.net.InetAddress} instances for each host.
      *
      * @return the {@link java.net.InetAddress} resolver
+     * @see Builder#inetAddressResolver(InetAddressResolver)
      * @since 4.10
      */
     @Nullable
@@ -660,6 +658,7 @@ public Builder dnsClient(@Nullable final DnsClient dnsClient) {
          *
          * @param inetAddressResolver the InetAddress provider
          * @return the {@link java.net.InetAddress} resolver
+         * @see #getInetAddressResolver()
          * @since 4.10
          */
         public Builder inetAddressResolver(@Nullable final InetAddressResolver inetAddressResolver) {

driver-core/src/main/com/mongodb/internal/connection/ServerAddressHelper.java

@@ -21,17 +21,27 @@
 import com.mongodb.MongoSocketException;
 import com.mongodb.ServerAddress;
 import com.mongodb.UnixServerAddress;
+import com.mongodb.lang.Nullable;
 import com.mongodb.spi.dns.InetAddressResolver;
+import com.mongodb.spi.dns.InetAddressResolverProvider;
 
 import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
 import java.util.List;
+import java.util.ServiceLoader;
 import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 
 /**
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
 public final class ServerAddressHelper {
+    @Nullable
+    private static final InetAddressResolver LOCATED_INET_ADDRESS_RESOLVER = StreamSupport.stream(
+            ServiceLoader.load(InetAddressResolverProvider.class).spliterator(), false)
+            .findFirst()
+            .map(InetAddressResolverProvider::create)
+            .orElse(null);
 
     public static ServerAddress createServerAddress(final String host) {
         return createServerAddress(host, ServerAddress.defaultPort());
@@ -46,8 +56,14 @@ public static ServerAddress createServerAddress(final String host, final int por
     }
 
     public static InetAddressResolver getInetAddressResolver(final MongoClientSettings settings) {
-        InetAddressResolver inetAddressResolver = settings.getInetAddressResolver();
-        return inetAddressResolver == null ? new DefaultInetAddressResolver() : inetAddressResolver;
+        InetAddressResolver explicitInetAddressResolver = settings.getInetAddressResolver();
+        if (explicitInetAddressResolver != null) {
+            return explicitInetAddressResolver;
+        } else if (LOCATED_INET_ADDRESS_RESOLVER != null) {
+            return LOCATED_INET_ADDRESS_RESOLVER;
+        } else {
+            return new DefaultInetAddressResolver();
+        }
     }
 
     public static List<InetSocketAddress> getSocketAddresses(final ServerAddress serverAddress, final InetAddressResolver resolver) {

driver-core/src/main/resources/META-INF/native-image/org.mongodb/bson/native-image.properties

@@ -13,4 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-Args = --initialize-at-run-time=com.mongodb.UnixServerAddress,com.mongodb.internal.connection.SnappyCompressor,org.bson.types.ObjectId,com.mongodb.internal.connection.ClientMetadataHelper
+Args =\
+  --initialize-at-run-time=\
+    com.mongodb.UnixServerAddress,\
+    com.mongodb.internal.connection.SnappyCompressor,\
+    com.mongodb.internal.connection.ClientMetadataHelper,\
+    com.mongodb.internal.connection.ServerAddressHelper

driver-core/src/main/resources/META-INF/native-image/resource-config.json

@@ -0,0 +1,7 @@
+{
+  "resources":{
+  "includes":[{
+    "pattern":"\\QMETA-INF/services/com.mongodb.spi.dns.InetAddressResolverProvider\\E"
+  }]},
+  "bundles":[]
+}

driver-core/src/test/unit/com/mongodb/connection/ServerAddressHelperTest.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.mongodb.connection;
+
+import com.mongodb.MongoClientSettings;
+import com.mongodb.internal.connection.DefaultInetAddressResolver;
+import com.mongodb.internal.connection.ServerAddressHelper;
+import com.mongodb.spi.dns.InetAddressResolver;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+final class ServerAddressHelperTest {
+    @Test
+    void getInetAddressResolver() {
+        assertAll(
+                () -> assertEquals(
+                        DefaultInetAddressResolver.class,
+                        ServerAddressHelper.getInetAddressResolver(MongoClientSettings.builder().build()).getClass()),
+                () -> {
+                    InetAddressResolver resolver = new DefaultInetAddressResolver();
+                    assertSame(
+                            resolver,
+                            ServerAddressHelper.getInetAddressResolver(MongoClientSettings.builder().inetAddressResolver(resolver).build()));
+                }
+        );
+    }
+}

graalvm-native-image-app/build.gradle

@@ -51,9 +51,8 @@ graalvmNative {
         configureEach {
             buildArgs.add('--strict-image-heap')
             buildArgs.add('-H:+UnlockExperimentalVMOptions')
-            // see class initialization report is generated at `graalvm/build/native/nativeCompile/reports`,
-            // informing us on the kind of initialization for each Java class
-            buildArgs.add('-H:+PrintClassInitialization')
+            // see class initialization and other reports in `graalvm/build/native/nativeCompile/reports`
+            buildArgs.add('--diagnostics-mode')
             // see the "registerResource" entries in the `native-image` built-time output,
             // informing us on the resources included in the native image being built
             buildArgs.add('-H:Log=registerResource:5')

graalvm-native-image-app/src/main/com/mongodb/internal/graalvm/CustomInetAddressResolverProvider.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.mongodb.internal.graalvm;
+
+import com.mongodb.internal.connection.DefaultInetAddressResolver;
+import com.mongodb.spi.dns.InetAddressResolver;
+import com.mongodb.spi.dns.InetAddressResolverProvider;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.List;
+
+import static java.lang.String.format;
+
+public final class CustomInetAddressResolverProvider implements InetAddressResolverProvider {
+    private static volatile boolean used = false;
+
+    public CustomInetAddressResolverProvider() {
+    }
+
+    @Override
+    public InetAddressResolver create() {
+        return new CustomInetAddressResolver();
+    }
+
+    static void assertUsed() throws AssertionError {
+        if (!used) {
+            throw new AssertionError(format("%s is not used", CustomInetAddressResolverProvider.class.getSimpleName()));
+        }
+    }
+
+    private static void markUsed() {
+        used = true;
+    }
+
+    private static final class CustomInetAddressResolver implements InetAddressResolver {
+        private final DefaultInetAddressResolver wrapped;
+
+        CustomInetAddressResolver() {
+            wrapped = new DefaultInetAddressResolver();
+        }
+
+        @Override
+        public List<InetAddress> lookupByName(final String host) throws UnknownHostException {
+            markUsed();
+            return wrapped.lookupByName(host);
+        }
+    }
+}

graalvm-native-image-app/src/main/com/mongodb/internal/graalvm/DnsSpi.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.mongodb.internal.graalvm;
+
+import com.mongodb.client.MongoClient;
+import com.mongodb.client.MongoClients;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+
+final class DnsSpi {
+    private static final Logger LOGGER = LoggerFactory.getLogger(DnsSpi.class);
+
+    public static void main(final String... args) {
+        LOGGER.info("Begin");
+        try (MongoClient client = args.length == 0 ? MongoClients.create() : MongoClients.create(args[0])) {
+            LOGGER.info("Database names: {}", client.listDatabaseNames().into(new ArrayList<>()));
+        }
+        CustomInetAddressResolverProvider.assertUsed();
+        LOGGER.info("End");
+    }
+
+    private DnsSpi() {
+    }
+}

graalvm-native-image-app/src/main/com/mongodb/internal/graalvm/NativeImageApp.java

@@ -29,11 +29,14 @@ final class NativeImageApp {
     private static final Logger LOGGER = LoggerFactory.getLogger(NativeImageApp.class);
 
     public static void main(final String[] args) {
+        LOGGER.info("Begin");
         LOGGER.info("java.vendor={}, java.vm.name={}, java.version={}",
                 System.getProperty("java.vendor"), System.getProperty("java.vm.name"), System.getProperty("java.version"));
         String[] arguments = new String[] {getConnectionStringSystemPropertyOrDefault()};
         LOGGER.info("proper args={}, tour/example arguments={}", Arrays.toString(args), Arrays.toString(arguments));
         List<Throwable> errors = Stream.<ThrowingRunnable>of(
+                new ThrowingRunnable.Named(DnsSpi.class,
+                        () -> DnsSpi.main(arguments)),
                 new ThrowingRunnable.Named(gridfs.GridFSTour.class,
                         () -> gridfs.GridFSTour.main(arguments)),
                 new ThrowingRunnable.Named(documentation.CausalConsistencyExamples.class,
@@ -85,6 +88,7 @@ public static void main(final String[] args) {
             errors.forEach(error::addSuppressed);
             throw error;
         }
+        LOGGER.info("End");
     }
 
     private NativeImageApp() {

graalvm-native-image-app/src/main/com/mongodb/internal/graalvm/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2008-present MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@NonNullApi
+package com.mongodb.internal.graalvm;
+
+import com.mongodb.lang.NonNullApi;

graalvm-native-image-app/src/main/resources/META-INF/services/com.mongodb.spi.dns.InetAddressResolverProvider

@@ -0,0 +1 @@
+com.mongodb.internal.graalvm.CustomInetAddressResolverProvider