Round-robin DNS resolution

pom.xml

@@ -55,6 +55,11 @@
                 <artifactId>netty-handler-proxy</artifactId>
                 <version>${netty.version}</version>
             </dependency>
+            <dependency>
+                <groupId>io.netty</groupId>
+                <artifactId>netty-resolver-dns</artifactId>
+                <version>${netty.version}</version>
+            </dependency>
             <dependency>
                 <groupId>io.netty</groupId>
                 <artifactId>netty-tcnative-boringssl-static</artifactId>

pushy/pom.xml

@@ -43,6 +43,10 @@
             <groupId>io.netty</groupId>
             <artifactId>netty-handler-proxy</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.netty</groupId>
+            <artifactId>netty-resolver-dns</artifactId>
+        </dependency>
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-tcnative-boringssl-static</artifactId>

pushy/src/main/java/com/turo/pushy/apns/ApnsChannelFactory.java

@@ -33,8 +33,9 @@
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslHandler;
 import io.netty.handler.timeout.IdleStateHandler;
-import io.netty.resolver.DefaultAddressResolverGroup;
 import io.netty.resolver.NoopAddressResolverGroup;
+import io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider;
+import io.netty.resolver.dns.RoundRobinDnsAddressResolverGroup;
 import io.netty.util.AttributeKey;
 import io.netty.util.ReferenceCounted;
 import io.netty.util.concurrent.Future;
@@ -84,7 +85,8 @@ class ApnsChannelFactory implements PooledObjectFactory<Channel>, Closeable {
         this.bootstrapTemplate.option(ChannelOption.TCP_NODELAY, true);
         this.bootstrapTemplate.remoteAddress(apnsServerAddress);
         this.bootstrapTemplate.resolver(proxyHandlerFactory == null ?
-                DefaultAddressResolverGroup.INSTANCE : NoopAddressResolverGroup.INSTANCE);
+                new RoundRobinDnsAddressResolverGroup(ClientChannelClassUtil.getDatagramChannelClass(eventLoopGroup),
+                        DefaultDnsServerAddressStreamProvider.INSTANCE) : NoopAddressResolverGroup.INSTANCE);
 
         if (connectTimeoutMillis > 0) {
             this.bootstrapTemplate.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, connectTimeoutMillis);
@@ -186,7 +188,7 @@ public void run() {
 
                 final Bootstrap bootstrap = ApnsChannelFactory.this.bootstrapTemplate.clone()
                         .channelFactory(new AugmentingReflectiveChannelFactory<>(
-                                ClientSocketChannelClassUtil.getSocketChannelClass(ApnsChannelFactory.this.bootstrapTemplate.config().group()),
+                                ClientChannelClassUtil.getSocketChannelClass(ApnsChannelFactory.this.bootstrapTemplate.config().group()),
                                 CHANNEL_READY_PROMISE_ATTRIBUTE_KEY, channelReadyPromise));
 
                 final ChannelFuture connectFuture = bootstrap.connect();

pushy/src/main/java/com/turo/pushy/apns/ClientChannelClassUtil.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2013-2017 Turo
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.turo.pushy.apns;
+
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.socket.DatagramChannel;
+import io.netty.channel.socket.SocketChannel;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+class ClientChannelClassUtil {
+
+    private static final Map<String, String> SOCKET_CHANNEL_CLASSES = new HashMap<>();
+    private static final Map<String, String> DATAGRAM_CHANNEL_CLASSES = new HashMap<>();
+
+    static {
+        SOCKET_CHANNEL_CLASSES.put("io.netty.channel.nio.NioEventLoopGroup", "io.netty.channel.socket.nio.NioSocketChannel");
+        SOCKET_CHANNEL_CLASSES.put("io.netty.channel.oio.OioEventLoopGroup", "io.netty.channel.socket.oio.OioSocketChannel");
+        SOCKET_CHANNEL_CLASSES.put("io.netty.channel.epoll.EpollEventLoopGroup", "io.netty.channel.epoll.EpollSocketChannel");
+        SOCKET_CHANNEL_CLASSES.put("io.netty.channel.kqueue.KQueueEventLoopGroup", "io.netty.channel.kqueue.KQueueSocketChannel");
+
+        DATAGRAM_CHANNEL_CLASSES.put("io.netty.channel.nio.NioEventLoopGroup", "io.netty.channel.socket.nio.NioDatagramChannel");
+        DATAGRAM_CHANNEL_CLASSES.put("io.netty.channel.oio.OioEventLoopGroup", "io.netty.channel.socket.oio.OioDatagramChannel");
+        DATAGRAM_CHANNEL_CLASSES.put("io.netty.channel.epoll.EpollEventLoopGroup", "io.netty.channel.epoll.EpollDatagramChannel");
+        DATAGRAM_CHANNEL_CLASSES.put("io.netty.channel.kqueue.KQueueEventLoopGroup", "io.netty.channel.kqueue.KQueueDatagramChannel");
+    }
+
+    /**
+     * Returns a socket channel class suitable for specified event loop group.
+     *
+     * @param eventLoopGroup the event loop group for which to identify an appropriate socket channel class; must not
+     * be {@code null}
+     *
+     * @return a socket channel class suitable for use with the given event loop group
+     *
+     * @throws IllegalArgumentException in case of null or unrecognized event loop group
+     */
+    static Class<? extends SocketChannel> getSocketChannelClass(final EventLoopGroup eventLoopGroup) {
+        Objects.requireNonNull(eventLoopGroup);
+
+        final String socketChannelClassName = SOCKET_CHANNEL_CLASSES.get(eventLoopGroup.getClass().getName());
+
+        if (socketChannelClassName == null) {
+            throw new IllegalArgumentException("No socket channel class found for event loop group type: " + eventLoopGroup.getClass().getName());
+        }
+
+        try {
+            return Class.forName(socketChannelClassName).asSubclass(SocketChannel.class);
+        } catch (final ClassNotFoundException e) {
+            throw new IllegalArgumentException(e);
+        }
+    }
+
+    /**
+     * Returns a datagram channel class suitable for specified event loop group.
+     *
+     * @param eventLoopGroup the event loop group for which to identify an appropriate datagram channel class; must not
+     * be {@code null}
+     *
+     * @return a datagram channel class suitable for use with the given event loop group
+     *
+     * @throws IllegalArgumentException in case of null or unrecognized event loop group
+     */
+    static Class<? extends DatagramChannel> getDatagramChannelClass(final EventLoopGroup eventLoopGroup) {
+        Objects.requireNonNull(eventLoopGroup);
+
+        final String datagramChannelClassName = DATAGRAM_CHANNEL_CLASSES.get(eventLoopGroup.getClass().getName());
+
+        if (datagramChannelClassName == null) {
+            throw new IllegalArgumentException("No datagram channel class found for event loop group type: " + eventLoopGroup.getClass().getName());
+        }
+
+        try {
+            return Class.forName(datagramChannelClassName).asSubclass(DatagramChannel.class);
+        } catch (final ClassNotFoundException e) {
+            throw new IllegalArgumentException(e);
+        }
+    }
+}

pushy/src/main/java/com/turo/pushy/apns/server/ServerSocketChannelClassUtil.java

@@ -22,23 +22,23 @@
 
 package com.turo.pushy.apns.server;
 
-import io.netty.channel.Channel;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.ServerChannel;
-import io.netty.channel.nio.NioEventLoopGroup;
-import io.netty.channel.oio.OioEventLoopGroup;
-import io.netty.channel.socket.nio.NioServerSocketChannel;
-import io.netty.channel.socket.oio.OioServerSocketChannel;
 
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Objects;
 
 class ServerSocketChannelClassUtil {
 
-    private static final String EPOLL_EVENT_LOOP_GROUP_CLASS = "io.netty.channel.epoll.EpollEventLoopGroup";
-    private static final String EPOLL_SERVER_SOCKET_CHANNEL_CLASS = "io.netty.channel.epoll.EpollServerSocketChannel";
+    private static final Map<String, String> SERVER_SOCKET_CHANNEL_CLASSES = new HashMap<>();
 
-    private static final String KQUEUE_EVENT_LOOP_GROUP_CLASS = "io.netty.channel.kqueue.KQueueEventLoopGroup";
-    private static final String KQUEUE_SERVER_SOCKET_CHANNEL_CLASS = "io.netty.channel.kqueue.KQueueServerSocketChannel";
+    static {
+        SERVER_SOCKET_CHANNEL_CLASSES.put("io.netty.channel.nio.NioEventLoopGroup", "io.netty.channel.socket.nio.NioServerSocketChannel");
+        SERVER_SOCKET_CHANNEL_CLASSES.put("io.netty.channel.oio.OioEventLoopGroup", "io.netty.channel.socket.oio.OioServerSocketChannel");
+        SERVER_SOCKET_CHANNEL_CLASSES.put("io.netty.channel.epoll.EpollEventLoopGroup", "io.netty.channel.epoll.EpollServerSocketChannel");
+        SERVER_SOCKET_CHANNEL_CLASSES.put("io.netty.channel.kqueue.KQueueEventLoopGroup", "io.netty.channel.kqueue.KQueueServerSocketChannel");
+    }
 
     /**
      * Returns a server socket channel class suitable for specified event loop group.
@@ -54,26 +54,14 @@ class ServerSocketChannelClassUtil {
     static Class<? extends ServerChannel> getServerSocketChannelClass(final EventLoopGroup eventLoopGroup) {
         Objects.requireNonNull(eventLoopGroup);
 
-        final Class<? extends ServerChannel> serverSocketChannelClass;
+        final String serverSocketChannelClassName = SERVER_SOCKET_CHANNEL_CLASSES.get(eventLoopGroup.getClass().getName());
 
-        if (eventLoopGroup instanceof NioEventLoopGroup) {
-            serverSocketChannelClass = NioServerSocketChannel.class;
-        } else if (eventLoopGroup instanceof OioEventLoopGroup) {
-            serverSocketChannelClass = OioServerSocketChannel.class;
-        } else if (EPOLL_EVENT_LOOP_GROUP_CLASS.equals(eventLoopGroup.getClass().getName())) {
-            serverSocketChannelClass = (Class<? extends ServerChannel>) loadSocketChannelClass(EPOLL_SERVER_SOCKET_CHANNEL_CLASS);
-        } else if (KQUEUE_EVENT_LOOP_GROUP_CLASS.equals(eventLoopGroup.getClass().getName())) {
-            serverSocketChannelClass = (Class<? extends ServerChannel>) loadSocketChannelClass(KQUEUE_SERVER_SOCKET_CHANNEL_CLASS);
-        } else {
-            throw new IllegalArgumentException("Could not find server socket class for event loop group class: " + eventLoopGroup.getClass().getName());
+        if (serverSocketChannelClassName == null) {
+            throw new IllegalArgumentException("No server socket channel class found for event loop group type: " + eventLoopGroup.getClass().getName());
         }
 
-        return serverSocketChannelClass;
-    }
-
-    private static Class<? extends Channel> loadSocketChannelClass(final String className) {
         try {
-            return Class.forName(className).asSubclass(Channel.class);
+            return Class.forName(serverSocketChannelClassName).asSubclass(ServerChannel.class);
         } catch (final ClassNotFoundException e) {
             throw new IllegalArgumentException(e);
         }