Implement fallback to IPv4/IPv6 vice-versa for sync

This commit changes the way the driver attempts connections to the
ip addresses that are associated with a host. Instead of only fetching
the first ip address and attempting a connection that single ip address,
the driver will now fetch all of the ip addresses and attempt to
connect to each one until a successful connection is made, or until
it is determined that none of the ip addresses can be connected to.
Note that this commit is only for sync. The implementation of this
for async will be handled in a separate commit. A couple of tests
were added for this change as well.

JAVA-2700

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

@@ -23,6 +23,8 @@
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * Represents the location of a Mongo server - i.e. server name and port number
@@ -189,6 +191,27 @@ public InetSocketAddress getSocketAddress() {
         }
     }
 
+    /**
+     * Gets all underlying socket addresses
+     *
+     * @return array of socket addresses
+     *
+     * @since 3.9
+     */
+    public List<InetSocketAddress> getSocketAddresses() {
+        try {
+            InetAddress[] inetAddresses = InetAddress.getAllByName(host);
+            List<InetSocketAddress> inetSocketAddressList = new ArrayList<InetSocketAddress>();
+            for (InetAddress inetAddress : inetAddresses) {
+                inetSocketAddressList.add(new InetSocketAddress(inetAddress, port));
+            }
+
+            return inetSocketAddressList;
+        } catch (UnknownHostException e) {
+            throw new MongoSocketException(e.getMessage(), this, e);
+        }
+    }
+
     @Override
     public String toString() {
         return host + ":" + port;

driver-core/src/main/com/mongodb/connection/netty/NettyStream.java

@@ -127,7 +127,7 @@ public void initChannel(final SocketChannel ch) throws Exception {
                     SSLEngine engine = getSslContext().createSSLEngine(address.getHost(), address.getPort());
                     engine.setUseClientMode(true);
                     SSLParameters sslParameters = engine.getSSLParameters();
-                    enableSni(address, sslParameters);
+                    enableSni(address.getHost(), sslParameters);
                     if (!sslSettings.isInvalidHostNameAllowed()) {
                         enableHostNameVerification(sslParameters);
                     }

driver-core/src/main/com/mongodb/internal/connection/Java8SniSslHelper.java

@@ -16,8 +16,6 @@
 
 package com.mongodb.internal.connection;
 
-import com.mongodb.ServerAddress;
-
 import javax.net.ssl.SNIHostName;
 import javax.net.ssl.SNIServerName;
 import javax.net.ssl.SSLParameters;
@@ -37,9 +35,9 @@ final class Java8SniSslHelper implements SniSslHelper {
     }
 
     @Override
-    public void enableSni(final ServerAddress address, final SSLParameters sslParameters) {
+    public void enableSni(final String host, final SSLParameters sslParameters) {
         try {
-            SNIServerName sniHostName = new SNIHostName(address.getHost());
+            SNIServerName sniHostName = new SNIHostName(host);
             sslParameters.setServerNames(singletonList(sniHostName));
         } catch (IllegalArgumentException e) {
             // ignore because SNIHostName will throw this for some legit host names for connecting to MongoDB, e.g an IPV6 literal

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

@@ -16,17 +16,15 @@
 
 package com.mongodb.internal.connection;
 
-import com.mongodb.ServerAddress;
-
 import javax.net.ssl.SSLParameters;
 
 interface SniSslHelper {
 
     /**
      * Enable SNI.
      *
-     * @param address       the server address
+     * @param host          the server host
      * @param sslParameters the SSL parameters
      */
-    void enableSni(ServerAddress address, SSLParameters sslParameters);
+    void enableSni(String host, SSLParameters sslParameters);
 }

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

@@ -16,6 +16,7 @@
 
 package com.mongodb.internal.connection;
 
+import com.mongodb.MongoSocketException;
 import com.mongodb.MongoSocketOpenException;
 import com.mongodb.MongoSocketReadException;
 import com.mongodb.ServerAddress;
@@ -27,8 +28,11 @@
 import org.bson.ByteBuf;
 
 import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.SocketTimeoutException;
 import java.nio.ByteBuffer;
 import java.nio.channels.SocketChannel;
+import java.util.Iterator;
 import java.util.List;
 
 import static com.mongodb.assertions.Assertions.isTrue;
@@ -51,16 +55,32 @@ public SocketChannelStream(final ServerAddress address, final SocketSettings set
     }
 
     @Override
-    public void open() throws IOException {
+    public void open() {
         try {
-            socketChannel = SocketChannel.open();
-            SocketStreamHelper.initialize(socketChannel.socket(), address, settings, sslSettings);
+            socketChannel = initializeSocketChannel();
         } catch (IOException e) {
             close();
             throw new MongoSocketOpenException("Exception opening socket", getAddress(), e);
         }
     }
 
+    private SocketChannel initializeSocketChannel() throws IOException {
+        Iterator<InetSocketAddress> inetSocketAddresses = address.getSocketAddresses().iterator();
+        while (inetSocketAddresses.hasNext()) {
+            SocketChannel socketChannel = SocketChannel.open();
+            try {
+                SocketStreamHelper.initialize(socketChannel.socket(), inetSocketAddresses.next(), settings, sslSettings);
+                return socketChannel;
+            } catch (SocketTimeoutException e) {
+                if (!inetSocketAddresses.hasNext()) {
+                    throw e;
+                }
+            }
+        }
+
+        throw new MongoSocketException("Exception opening socket", getAddress());
+    }
+
     @Override
     public ByteBuf getBuffer(final int size) {
         return bufferProvider.getBuffer(size);

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

@@ -16,6 +16,7 @@
 
 package com.mongodb.internal.connection;
 
+import com.mongodb.MongoSocketException;
 import com.mongodb.MongoSocketOpenException;
 import com.mongodb.MongoSocketReadException;
 import com.mongodb.ServerAddress;
@@ -30,7 +31,10 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.net.SocketTimeoutException;
+import java.util.Iterator;
 import java.util.List;
 
 import static com.mongodb.assertions.Assertions.notNull;
@@ -56,10 +60,9 @@ public SocketStream(final ServerAddress address, final SocketSettings settings,
     }
 
     @Override
-    public void open() throws IOException {
+    public void open() {
         try {
-            socket = socketFactory.createSocket();
-            SocketStreamHelper.initialize(socket, address, settings, sslSettings);
+            socket = initializeSocket();
             outputStream = socket.getOutputStream();
             inputStream = socket.getInputStream();
         } catch (IOException e) {
@@ -68,6 +71,23 @@ public void open() throws IOException {
         }
     }
 
+    private Socket initializeSocket() throws IOException {
+        Iterator<InetSocketAddress> inetSocketAddresses = address.getSocketAddresses().iterator();
+        while (inetSocketAddresses.hasNext()) {
+            Socket socket = socketFactory.createSocket();
+            try {
+                SocketStreamHelper.initialize(socket, inetSocketAddresses.next(), settings, sslSettings);
+                return socket;
+            } catch (SocketTimeoutException e) {
+                if (!inetSocketAddresses.hasNext()) {
+                    throw e;
+                }
+            }
+        }
+
+        throw new MongoSocketException("Exception opening socket", getAddress());
+    }
+
     @Override
     public ByteBuf getBuffer(final int size) {
         return bufferProvider.getBuffer(size);

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

@@ -17,13 +17,13 @@
 package com.mongodb.internal.connection;
 
 import com.mongodb.MongoInternalException;
-import com.mongodb.ServerAddress;
 import com.mongodb.connection.SocketSettings;
 import com.mongodb.connection.SslSettings;
 
 import javax.net.ssl.SSLParameters;
 import javax.net.ssl.SSLSocket;
 import java.io.IOException;
+import java.net.InetSocketAddress;
 import java.net.Socket;
 
 import static com.mongodb.internal.connection.SslHelper.enableHostNameVerification;
@@ -33,8 +33,8 @@
 final class SocketStreamHelper {
 
     @SuppressWarnings("deprecation")
-    static void initialize(final Socket socket, final ServerAddress address, final SocketSettings settings, final SslSettings sslSettings)
-    throws IOException {
+    static void initialize(final Socket socket, final InetSocketAddress inetSocketAddress, final SocketSettings settings,
+                           final SslSettings sslSettings) throws IOException {
         socket.setTcpNoDelay(true);
         socket.setSoTimeout(settings.getReadTimeout(MILLISECONDS));
         socket.setKeepAlive(settings.isKeepAlive());
@@ -54,14 +54,14 @@ static void initialize(final Socket socket, final ServerAddress address, final S
                 sslParameters = new SSLParameters();
             }
 
-            enableSni(address, sslParameters);
+            enableSni(inetSocketAddress.getHostName(), sslParameters);
 
             if (!sslSettings.isInvalidHostNameAllowed()) {
                 enableHostNameVerification(sslParameters);
             }
             sslSocket.setSSLParameters(sslParameters);
         }
-        socket.connect(address.getSocketAddress(), settings.getConnectTimeout(MILLISECONDS));
+        socket.connect(inetSocketAddress, settings.getConnectTimeout(MILLISECONDS));
     }
 
     private SocketStreamHelper() {

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

@@ -16,8 +16,6 @@
 
 package com.mongodb.internal.connection;
 
-import com.mongodb.ServerAddress;
-
 import javax.net.ssl.SSLParameters;
 import java.lang.reflect.InvocationTargetException;
 
@@ -69,12 +67,12 @@ public static void enableHostNameVerification(final SSLParameters sslParameters)
     /**
      * Enable SNI if running on Java 8 or later.  Otherwise fail silently to enable SNI.
      *
-     * @param address       the server address
+     * @param host          the server host
      * @param sslParameters the SSL parameters
      */
-    public static void enableSni(final ServerAddress address, final SSLParameters sslParameters) {
+    public static void enableSni(final String host, final SSLParameters sslParameters) {
         if (SNI_SSL_HELPER != null) {
-            SNI_SSL_HELPER.enableSni(address, sslParameters);
+            SNI_SSL_HELPER.enableSni(host, sslParameters);
         }
     }
 

driver-core/src/test/functional/com/mongodb/internal/connection/SocketStreamHelperSpecification.groovy

@@ -45,7 +45,7 @@ class SocketStreamHelperSpecification extends Specification {
                 .build()
 
         when:
-        SocketStreamHelper.initialize(socket, getPrimary(), socketSettings, SslSettings.builder().build())
+        SocketStreamHelper.initialize(socket, getPrimary().getSocketAddress(), socketSettings, SslSettings.builder().build())
 
         then:
         socket.getTcpNoDelay()
@@ -61,7 +61,8 @@ class SocketStreamHelperSpecification extends Specification {
         Socket socket = SocketFactory.default.createSocket()
 
         when:
-        SocketStreamHelper.initialize(socket, getPrimary(), SocketSettings.builder().build(), SslSettings.builder().build())
+        SocketStreamHelper.initialize(socket, getPrimary().getSocketAddress(),
+                SocketSettings.builder().build(), SslSettings.builder().build())
 
         then:
         socket.isConnected()
@@ -76,7 +77,7 @@ class SocketStreamHelperSpecification extends Specification {
         SSLSocket socket = SSLSocketFactory.default.createSocket()
 
         when:
-        SocketStreamHelper.initialize(socket, getPrimary(), SocketSettings.builder().build(), sslSettings)
+        SocketStreamHelper.initialize(socket, getPrimary().getSocketAddress(), SocketSettings.builder().build(), sslSettings)
 
         then:
         socket.getSSLParameters().endpointIdentificationAlgorithm == (sslSettings.invalidHostNameAllowed ? null : 'HTTPS')
@@ -96,7 +97,7 @@ class SocketStreamHelperSpecification extends Specification {
         SSLSocket socket = SSLSocketFactory.default.createSocket()
 
         when:
-        SocketStreamHelper.initialize(socket, getPrimary(), SocketSettings.builder().build(), sslSettings)
+        SocketStreamHelper.initialize(socket, getPrimary().getSocketAddress(), SocketSettings.builder().build(), sslSettings)
 
         then:
         socket.getSSLParameters().getServerNames() == [new SNIHostName(getPrimary().getHost())]
@@ -114,7 +115,8 @@ class SocketStreamHelperSpecification extends Specification {
         Socket socket = SocketFactory.default.createSocket()
 
         when:
-        SocketStreamHelper.initialize(socket, getPrimary(), SocketSettings.builder().build(), SslSettings.builder().enabled(true).build())
+        SocketStreamHelper.initialize(socket, getPrimary().getSocketAddress(), SocketSettings.builder().build(),
+                SslSettings.builder().enabled(true).build())
 
         then:
         thrown(MongoInternalException)