DNS discovery fixes

.gitignore

@@ -27,3 +27,5 @@ enterprise/server-enterprise/neo4j-home
 integrationtests/data
 dependency-reduced-pom.xml
 venv
+testkit-backend/bin/
+testkit/CAs/

driver/src/main/java/org/neo4j/driver/internal/BoltServerAddress.java

@@ -18,19 +18,13 @@
  */
 package org.neo4j.driver.internal;
 
-import java.net.InetAddress;
-import java.net.InetSocketAddress;
-import java.net.SocketAddress;
 import java.net.URI;
-import java.net.UnknownHostException;
-import java.util.List;
 import java.util.Objects;
 import java.util.stream.Stream;
 
 import org.neo4j.driver.net.ServerAddress;
 
 import static java.util.Objects.requireNonNull;
-import static java.util.stream.Collectors.toList;
 
 /**
  * Holds a host and port pair that denotes a Bolt server address.
@@ -40,12 +34,11 @@ public class BoltServerAddress implements ServerAddress
     public static final int DEFAULT_PORT = 7687;
     public static final BoltServerAddress LOCAL_DEFAULT = new BoltServerAddress( "localhost", DEFAULT_PORT );
 
-    private final String host; // This could either be the same as originalHost or it is an IP address resolved from the original host.
-    private final int port;
+    protected final String host; // Host or IP address.
+    private final String connectionHost; // Either is equal to the host or is explicitly provided on creation and is expected to be a resolved IP address.
+    protected final int port;
     private final String stringValue;
 
-    private InetAddress resolved;
-
     public BoltServerAddress( String address )
     {
         this( uriFrom( address ) );
@@ -58,15 +51,17 @@ public BoltServerAddress( URI uri )
 
     public BoltServerAddress( String host, int port )
     {
-        this( host, null, port );
+        this( host, host, port );
     }
 
-    private BoltServerAddress( String host, InetAddress resolved, int port )
+    public BoltServerAddress( String host, String connectionHost, int port )
     {
         this.host = requireNonNull( host, "host" );
-        this.resolved = resolved;
+        this.connectionHost = requireNonNull( connectionHost, "connectionHost" );
         this.port = requireValidPort( port );
-        this.stringValue = resolved != null ? String.format( "%s(%s):%d", host, resolved.getHostAddress(), port ) : String.format( "%s:%d", host, port );
+        this.stringValue = host.equals( connectionHost )
+                           ? String.format( "%s:%d", host, port )
+                           : String.format( "%s(%s):%d", host, connectionHost, port );
     }
 
     public static BoltServerAddress from( ServerAddress address )
@@ -87,14 +82,14 @@ public boolean equals( Object o )
         {
             return false;
         }
-        BoltServerAddress that = (BoltServerAddress) o;
-        return port == that.port && host.equals( that.host );
+        BoltServerAddress address = (BoltServerAddress) o;
+        return port == address.port && host.equals( address.host ) && connectionHost.equals( address.connectionHost );
     }
 
     @Override
     public int hashCode()
     {
-        return Objects.hash( host, port );
+        return Objects.hash( host, connectionHost, port );
     }
 
     @Override
@@ -103,44 +98,6 @@ public String toString()
         return stringValue;
     }
 
-    /**
-     * Create a {@link SocketAddress} from this bolt address. This method always attempts to resolve the hostname into
-     * an {@link InetAddress}.
-     *
-     * @return new socket address.
-     * @see InetSocketAddress
-     */
-    public SocketAddress toSocketAddress()
-    {
-        return resolved == null ? new InetSocketAddress( host, port ) : new InetSocketAddress( resolved, port );
-    }
-
-    /**
-     * Resolve the host name down to an IP address
-     *
-     * @return a new address instance
-     * @throws UnknownHostException if no IP address for the host could be found
-     * @see InetAddress#getByName(String)
-     */
-    public BoltServerAddress resolve() throws UnknownHostException
-    {
-        return new BoltServerAddress( host, InetAddress.getByName( host ), port );
-    }
-
-    /**
-     * Resolve the host name down to all IP addresses that can be resolved to
-     *
-     * @return an array of new address instances that holds resolved addresses
-     * @throws UnknownHostException if no IP address for the host could be found
-     * @see InetAddress#getAllByName(String)
-     */
-    public List<BoltServerAddress> resolveAll() throws UnknownHostException
-    {
-        return Stream.of( InetAddress.getAllByName( host ) )
-                .map( address -> new BoltServerAddress( host, address, port ) )
-                .collect( toList() );
-    }
-
     @Override
     public String host()
     {
@@ -153,9 +110,21 @@ public int port()
         return port;
     }
 
-    public boolean isResolved()
+    public String connectionHost()
+    {
+        return connectionHost;
+    }
+
+    /**
+     * Create a stream of unicast addresses.
+     * <p>
+     * While this implementation just returns a stream of itself, the subclasses may provide multiple addresses.
+     *
+     * @return stream of unicast addresses.
+     */
+    public Stream<BoltServerAddress> unicastStream()
     {
-        return resolved != null;
+        return Stream.of( this );
     }
 
     private static String hostFrom( URI uri )

driver/src/main/java/org/neo4j/driver/internal/DefaultDomainNameResolver.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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 org.neo4j.driver.internal;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public class DefaultDomainNameResolver implements DomainNameResolver
+{
+    private static final DefaultDomainNameResolver INSTANCE = new DefaultDomainNameResolver();
+
+    public static DefaultDomainNameResolver getInstance()
+    {
+        return INSTANCE;
+    }
+
+    private DefaultDomainNameResolver()
+    {
+    }
+
+    @Override
+    public InetAddress[] resolve( String name ) throws UnknownHostException
+    {
+        return InetAddress.getAllByName( name );
+    }
+}

driver/src/main/java/org/neo4j/driver/internal/DomainNameResolver.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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 org.neo4j.driver.internal;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+/**
+ * A resolver function used by the driver to resolve domain names.
+ */
+@FunctionalInterface
+public interface DomainNameResolver
+{
+    /**
+     * Resolve the given domain name to a set of addresses.
+     *
+     * @param name the name to resolve.
+     * @return the resolved addresses.
+     * @throws UnknownHostException must be thrown if the given name can not be resolved to at least one address.
+     */
+    InetAddress[] resolve( String name ) throws UnknownHostException;
+}

driver/src/main/java/org/neo4j/driver/internal/DriverFactory.java

@@ -127,7 +127,7 @@ protected static MetricsProvider createDriverMetrics( Config config, Clock clock
     protected ChannelConnector createConnector( ConnectionSettings settings, SecurityPlan securityPlan,
             Config config, Clock clock, RoutingContext routingContext )
     {
-        return new ChannelConnectorImpl( settings, securityPlan, config.logging(), clock, routingContext );
+        return new ChannelConnectorImpl( settings, securityPlan, config.logging(), clock, routingContext, getDomainNameResolver() );
     }
 
     private InternalDriver createDriver( URI uri, SecurityPlan securityPlan, BoltServerAddress address, ConnectionPool connectionPool,
@@ -210,7 +210,7 @@ protected LoadBalancer createLoadBalancer( BoltServerAddress address, Connection
         LoadBalancingStrategy loadBalancingStrategy = new LeastConnectedLoadBalancingStrategy( connectionPool, config.logging() );
         ServerAddressResolver resolver = createResolver( config );
         return new LoadBalancer( address, routingSettings, connectionPool, eventExecutorGroup, createClock(),
-                config.logging(), loadBalancingStrategy, resolver );
+                                 config.logging(), loadBalancingStrategy, resolver, getDomainNameResolver() );
     }
 
     private static ServerAddressResolver createResolver( Config config )
@@ -271,6 +271,17 @@ protected Bootstrap createBootstrap( EventLoopGroup eventLoopGroup )
         return BootstrapFactory.newBootstrap( eventLoopGroup );
     }
 
+    /**
+     * Provides an instance of {@link DomainNameResolver} that is used for domain name resolution.
+     * <p>
+     * <b>This method is protected only for testing</b>
+     *
+     * @return the instance of {@link DomainNameResolver}.
+     */
+    protected DomainNameResolver getDomainNameResolver()
+    {
+        return DefaultDomainNameResolver.getInstance();
+    }
 
     private static void assertNoRoutingContext( URI uri, RoutingSettings routingSettings )
     {

driver/src/main/java/org/neo4j/driver/internal/ResolvedBoltServerAddress.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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 org.neo4j.driver.internal;
+
+import java.net.InetAddress;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Stream;
+
+import static java.util.Objects.requireNonNull;
+import static java.util.stream.Collectors.joining;
+
+/**
+ * An explicitly resolved version of {@link BoltServerAddress} that always contains one or more resolved IP addresses.
+ */
+public class ResolvedBoltServerAddress extends BoltServerAddress
+{
+    private static final String HOST_ADDRESSES_FORMAT = "%s%s:%d";
+    private static final int MAX_HOST_ADDRESSES_IN_STRING_VALUE = 5;
+    private static final String HOST_ADDRESS_DELIMITER = ",";
+    private static final String HOST_ADDRESSES_PREFIX = "(";
+    private static final String HOST_ADDRESSES_SUFFIX = ")";
+    private static final String TRIMMED_HOST_ADDRESSES_SUFFIX = ",..." + HOST_ADDRESSES_SUFFIX;
+
+    private final Set<InetAddress> resolvedAddresses;
+    private final String stringValue;
+
+    public ResolvedBoltServerAddress( String host, int port, InetAddress[] resolvedAddressesArr )
+    {
+        super( host, port );
+        requireNonNull( resolvedAddressesArr, "resolvedAddressesArr" );
+        if ( resolvedAddressesArr.length == 0 )
+        {
+            throw new IllegalArgumentException(
+                    "The resolvedAddressesArr must not be empty, check your DomainNameResolver is compliant with the interface contract" );
+        }
+        resolvedAddresses = Collections.unmodifiableSet( new LinkedHashSet<>( Arrays.asList( resolvedAddressesArr ) ) );
+        stringValue = createStringRepresentation();
+    }
+
+    /**
+     * Create a stream of unicast addresses.
+     * <p>
+     * The stream is created from the list of resolved IP addresses. Each unicast address is given a unique IP address as the connectionHost value.
+     *
+     * @return stream of unicast addresses.
+     */
+    @Override
+    public Stream<BoltServerAddress> unicastStream()
+    {
+        return resolvedAddresses.stream().map( address -> new BoltServerAddress( host, address.getHostAddress(), port ) );
+    }
+
+    @Override
+    public boolean equals( Object o )
+    {
+        if ( this == o )
+        {
+            return true;
+        }
+        if ( o == null || getClass() != o.getClass() )
+        {
+            return false;
+        }
+        if ( !super.equals( o ) )
+        {
+            return false;
+        }
+        ResolvedBoltServerAddress that = (ResolvedBoltServerAddress) o;
+        return resolvedAddresses.equals( that.resolvedAddresses );
+    }
+
+    @Override
+    public int hashCode()
+    {
+        return Objects.hash( super.hashCode(), resolvedAddresses );
+    }
+
+    @Override
+    public String toString()
+    {
+        return stringValue;
+    }
+
+    private String createStringRepresentation()
+    {
+        String hostAddresses = resolvedAddresses.stream()
+                                                .limit( MAX_HOST_ADDRESSES_IN_STRING_VALUE )
+                                                .map( InetAddress::getHostAddress )
+                                                .collect( joining( HOST_ADDRESS_DELIMITER, HOST_ADDRESSES_PREFIX,
+                                                                   resolvedAddresses.size() > MAX_HOST_ADDRESSES_IN_STRING_VALUE
+                                                                   ? TRIMMED_HOST_ADDRESSES_SUFFIX
+                                                                   : HOST_ADDRESSES_SUFFIX ) );
+        return String.format( HOST_ADDRESSES_FORMAT, host, hostAddresses, port );
+    }
+}